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Bauer, Wolfgang. "Understanding Spin Crossover: A Contribution." Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-131697.
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Bergen, Elvira [Verfasser]. "Multifunctional Spin Crossover Complexes / Elvira Bergen." Mainz : Universitätsbibliothek der Johannes Gutenberg-Universität Mainz, 2021. http://d-nb.info/1225796032/34.
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Craig, Gavin. "Advanced Study of Switchable Spin Crossover Compounds." Doctoral thesis, Universitat de Barcelona, 2013. http://hdl.handle.net/10803/119688.
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Systems based on the organic ligand 3-bpp display a wide variety of magnetic behaviour, and have been studied in depth in the field of spin crossover (SCO). However, despite the apparent richness of SCO behaviour observed for 3-bpp systems, at the time of undertaking this thesis there were no published examples of the use of synthetic derivatives of 3-bpp in this field of research. This was remarked upon by Olguín and Brooker, who attributed this lack of 3-bpp analogues not to a lack of interest, but to “synthetic issues”. Therefore, the initial challenge set out was to develop a methodology that would allow the synthesis of functionalised 3-bpp ligands. Once obtained, these ligands would then be used for the generation of mononuclear Fe(II) compounds, with a view to study their macroscopic properties. Provided that this strategy was successful, and depending on the availability of structural data, an attempt would then be made to outline correlations between the observed magnetic properties and the relationship between the lattice entities, both spin-active and –inactive. The development of this work is detailed over the course of the ten Chapters. The first is an Introduction, primarily to the general field of SCO, the theory underlying its occurrence and its potential utility, but also describes the latest advances in the field before focussing on the family of 3-bpp systems.
Chapter 2 contains the synthetic procedures and experimental details for the physical characterisation of the compounds obtained. Chapter 3 then describes the development of the novel polypyrazolyl ligands that have been designed for the subsequent investigation of their coordination chemistry. The magneto-structural properties of a new [Fe(3-bpp)2]2+ salt are described, and the compound shown to display a gradual spin crossover.
Chapters 4 and 5 provide an in-depth study of a mononuclear compound, [Fe(H4L)2](ClO4)2•H2O•2(CH3)2CO (1), containing one of the polypyrazolyl ligands. A strongly cooperative spin transition is found to be intimately related to the structure and level of disorder within the lattice. This conclusion is supported by a description of the thermally trapped crystal structure. The photo-physical properties of 1 are then described, through the study of its meta-stable HS phase, which is distinct to the thermally trapped meta-stable HS phase. A Raman spectroscopy study of the system is then used to observe photo-switching within the hysteresis loop, and as a means of following the pressure-induced spin switch.
Chapters 6 and 7 use compound 1 as the basis of an investigation into the effect of varying the anions and solvents within the lattice on the magnetic properties and crystal packing. A case where the spin crossover becomes more cooperative on ageing the compound is described. Chapter 8 details the compounds obtained using another 3-bpp derivative, which results in the formation of distorted structures that do not display SCO.
In Chapter 9, the structural data provided by this thesis is collated with that found in the CSD for mononuclear Fe(II) systems with 3-bpp ligands. The data is then analysed from two points of view: a first, which involves previously defined parameters for the distortion of the cations, both in terms of their shape and in terms of the coordination sphere using Continuous Symmetry Measures. And a second, which uses Hirshfeld surface analysis to look at the bonding motifs and intermolecular interactions that are observed in the novel compounds obtained in this thesis. Chapter 10 offers conclusions based on the results obtained in this thesis.A pesar de la riqueza de los comportamientos de la transición de espín de los sistemas basados en el ligando 3-bpp, no se ha estudiado ningún derivado del ligando. Así pues, el reto inicial de esta tesis fue el de desarrollar ligandos derivados del 3-bpp. Estos se utilizarían en la síntesis de compuestos mononucleares de Fe(II), para estudiar sus propiedades macroscópicas. Este trabajo se detalla a lo largo de nueve capítulos. El capítulo 2 contiene los procedimientos experimentales para la síntesis y caracterización de los compuestos obtenidos. El capítulo 3 describe el desarrollo de los ligandos que fueron utilizados en la química de coordinación. Se detallan las propiedades magneto-estructurales de una nueva sal [Fe(3-bpp)2](ClO4)2 que presenta una transición de espín gradual. Los capítulos 4 y 5 estudian el compuesto [Fe(H4L)2](ClO4)2•H2O•2(CH3)2CO (1). Se observa que una transición de alta cooperatividad se asocia al desorden cristalográfico. Se procede a describir las propiedades foto-físicas del compuesto, mediante el estudio de su fase meta-estable de espín alto inducido por irradiación. Un estudio de espectroscopia de Raman se llevó a cabo, permitiendo así la observación de un proceso de “photo-switch” dentro del ciclo de histéresis. Los espectros obtenidos sirvieron para seguir la transición al aplicar una presión externa. Los capítulos 6 y 7 investigan el efecto de los aniones y disolventes sobre las propiedades magnéticas y el empaquetamiento estructural del compuesto 1. Se describe un caso dónde un proceso de envejecimiento del compuesto lleva a que se aumente su grado de cooperatividad. En el capítulo 8, se utiliza otro derivado del 3-bpp para preparar unos compuestos mononucleares de Fe(II). Debido a la deformación estructural presentada por estos compuestos, no se observa una transición de espín. En el capítulo 9, se recogen los datos estructurales obtenidos a lo largo de la tesis, y se combinan con los datos disponibles en el CSD para compuestos mononucleares de Fe(II). Se analizan los datos para medir la forma y distorsión de los cationes, y para estudiar los tipos de interacción intermolecular mediante los análisis de superficies de Hirshfeld. El capítulo 10 saca unas conclusiones basadas en los resultados descritos en los capítulos anteriores.
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Bauer, Wolfgang [Verfasser]. "Understanding Spin Crossover: A Contribution / Wolfgang Bauer." München : Verlag Dr. Hut, 2011. http://d-nb.info/1014848571/34.
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Tovee, Clare Anne. "Metal complexes exhibiting spin crossover and fluorescence." Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509875.
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Dong, Xu. "Ultrafast infrared spectroscopy applied to spin crossover materials." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S111/document.
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Ces dix dernières années ont vu émerger des avancées technologiques majeures, nous permettant capturer une image instantanée des processus physique. L'amélioration systématique de la résolution temporelle de ces instants, grâce aux lasers (de différente sorte) aux impulsions ultracourtes, a joué un rôle important dans l'exploration des transitions de phases photo-induites dans différents matériaux, et leur potentiel applicatif. Néanmoins, ce progrès technologique incontestable a poussé à ses limites notre capacité de décrire les phénomènes hors-équilibre très complexes qui pilotent les transitions. Ils sont intrinsèquement multi-échelles dans le temps et dans l'espace, s'étalant de la femtoseconde aux plusieurs jours, et de la dimension atomique jusqu'à celle d'un cristal macroscopique. Les expériences résolues en temps permettent de séparer temporellement différents dégrées de liberté et les phénomènes pilotés par ceux-ci, au lieu d'observer seulement leur moyenne statistique. La première étape (processus photo-induit) de cette séquence temporelle est liée à l'absorption d'un photon, la deuxième (élastique) est pilotée par la dilation du volume macroscopique du matériau, et la troisième étape (thermique) est due aux effets de chaleur. Cette approche séquentielle offre de nouvelles possibilités pour mieux comprendre comment impacter les matériaux de façon contrôlée et efficace. Les lasers opérant dans le moyen infrarouge (mid IR) permettent de suivre le déroulement d'une transition de phase par le changement de vibrations des molécules/liaisons ciblées. Cette spécificité au site moléculaire combinée avec la résolution en temps ultracourte devrait ouvrir une nouvelle fenêtre d'observation des phénomènes qui échappaient aux études scientifique. Ce travail de thèse a commencé exactement dans cet esprit. L'effort majeur a été dédié à l'application de la spectroscopie mid IR ultrarapide aux matériaux présentant une conversion de l'état de spin, [Fe(3-MeO-SalEen)]2PF6 en particulier. La principale difficulté de ce travail consistait à décrypter le contenu spectral des molécules hors-équilibre. Nous avons découvert que l'approche utilisé dans les spectroscopies résolues en temps de plus haute énergie (UV/VIS) ne suffit pas pour étudier la problématique posé dans le cadre de cette thèse. Une nouvelle approche a été pensée pour modéliser les spectres résolus en temps, et celle-ci consistait à séparer la réponse spectrale en deux contributions : le transfert de poids spectral, et un décalage spectral. J'ai pu démontrer que ces deux contributions suivent sensiblement le changement d'état de spin, et la pression (dilatation du volume). L'analyse de données basée sur ce modèle, corrobore les résultats obtenus jusqu'alors avec d'autres techniques. Sur l'échelle de temps ultracourts, plus difficile à modéliser, nous avons pu néanmoins résoudre très clairement le refroidissement vibrationnelle (VC) de l'état électronique haut spin -chaud. A ma connaissance, ce phénomène dans un système solide présentant crossover de spin n'a jamais été observé directementThe past few decades have seen great advancements in technology that allow us to capture the picture of a physical process, as the adage “seeing is believing” implies how people understand the world. The increasing temporal resolution of lasers played an important role in the study of materials, among which materials exhibiting photo-induced phase transition are of great importance thanks to their potential for future applications. However, as we proceed further and further in the investigation of the mechanism of phase transition, we found ourselves confronted with the very complex nature of phase transition dynamics. It is intrinsically multi-scale in time and space, from femtosecond to days and from atomic dimensions to macroscopic distances. Time resolved experiments disentangle different degrees of freedom and different phenomena in a step-like manner, rather than providing a statistical average. The first step is photo induced due to absorption of photons, the second step (elastic step) is pressure induced due to volume dilation, and the third step is temperature induced due to dissipation of heat. This step-like approach offers an opportunity to understand the mechanism, so that we could effectively impact the materials and possibly control phase transition. Mid IR lasers have a unique advantage of monitoring phase transition through vibrational modes on specific molecular sites. Implementing ultrafast mid IR spectroscopy in phase transition materials should be therefore very insightful in discovering new phenomena and revealing hidden mechanism. This PhD project, focusing on mid IR technique, started exactly in this context. The main effort is dedicated to the application of ultrafast mid IR spectroscopy to the spin crossover solids, [Fe(3-MeO-SalEen)]2PF6. The major challenge in this work was to comprehend the shape of transient mid IR spectra. We found out that this is conceptually different from the experiences accumulated in UV/VIS spectroscopy. A suitable model had to be developed, separating the transient IR spectra into two contributions: spectral weight transfer and spectral shift. I demonstrated that these two components are sensitive to the spin change and pressure effect (volume dilation), respectively. Data analysis based on the new model shows consistency with previously published results. On the ultrafast timescale, more difficult to fit our model to, vibrational cooling (VC) of electronically hot HS state has been very well resolved. To the best of my knowledge, direct observation of VC in solid state SCO compound by IR spectroscopy has not been reported earlier
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Thompson, Amber L. "Structure-property correlations in novel spin crossover materials." Thesis, Durham University, 2004. http://etheses.dur.ac.uk/2997/.
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In complexes where the energy difference between the high and low spin state of the metal is of the order of k(_b)T, temperature can be used to induce a spin crossover transition (SC). In some cases, at very low temperatures, irradiation can induce excitation to a meta-stable high spin state. At low temperatures, this Light-Induced Excited Spin-State Trapped (LIESST) state is generally long lived, enabling structural examination. The results presented herein refer to a wide range of iron(II) spin crossover materials which have been structurally studied in both thermal and light induced states. These fall into three categories; mononuclear, dinuclear and polymeric. The mononuclear complexes studied include FeL[H(_2)B(Pz)(_2)](_2) L = 2,2'-bipyridine (1) and 1,10-phenanthroline (2), of which 2 was found to undergo a change in symmetry in addition to the change in spin state, leading to a novel light induced polymorphism that has not been previously seen. Two dinuclear compounds with step transitions have been examined. While {[N(CN)(_2)](FeBpl)(_2)}(PF(_6))(_3) undergoes a gradual transition, the transitions in [Fe(Btz)(NCS)(_2)](_2)Bpmd are abrupt and the latter also undergoes LIESST but with a rapid relaxation that has not been observed previously with any other technique. While the origin of this relaxation is uncertain, the structure of this excited state has been studied under constant irradiation. The largest structural study of three dimensional SC materials has been carried out, including bimetallic polymers with [Au(CN)(_2)], [Ag(CN)(_2)]-, [Ag(_2)(CN)(_3)]- and [Pd(CN)(_4)](^2-) bridging ligands. These anionic bridges have been shown to enhance cooperativity between iron centres leading to abrupt transitions and hysteresis. These materials have been shown to undergo LIESST, crystalline state allosterism, and thermo-chromism. Such multi-property materials have a high potential for technological applications.
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Shepherd, Helena Jane. "Spin crossover under extreme conditions : a structural approach." Thesis, Durham University, 2009. http://etheses.dur.ac.uk/228/.
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Structural studies of several iron complexes that show spin crossover (SCO) properties are presented and intrinsic links between the structure and properties have been established for these systems. X-ray diffraction experiments of samples under extremes of temperature and pressure and after irradiation with laser light have been performed to characterise the structure of these various compounds. The incomplete thermal SCO observed in the dinuclear species [
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Money, Victoria A. "Structural studies of iron (II) spin crossover compounds." Thesis, Durham University, 2004. http://etheses.dur.ac.uk/2987/.
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The drive for ever smaller and faster computers has, in recent years, caused much research interest to be focussed on the development of new materials in which individual molecules or assemblies of molecules can be used for information processing. Materials which show spin crossover behaviour have great potential for use not only in molecular computing but also in applications such as optical switches and display devices and are of fundamental interest due to their importance in biological and geological systems. The results of comprehensive variable temperature and excited state crystallographic studies into the spin crossover behaviour of a family of iron (II) spin crossover complexes based on the 2,6-di(pyrazol-l-yl)pyridine ligand are presented herein. A fascinating aspect of spin crossover materials is their ability to undergo a transition from the low spin state to a metastable high spin state, with a very long lifetime, on irradiation. Crystallographic information on the structure of the metastable high spin state formed as a result of irradiation is very rare. Full structural analyses of the metastable state are reported for [FeLl(_2)](BF(_4))(_2), [Fe(L3)(_2)](BF(_4))(_2), [Fe(L3)(_2)](C1O(_4))(_2) and [Fe(L4)(_2)](BF(_4))(_2) (LI = 2,6- di(pyrazol-l-yl)pyridine, L3 = 2,6-(dipyrazol-l-yl)-4-hydroxymethylpyridine, L4 = 2,6-di(3-methylpyrazol-1 -yl)pyridine). These studies have shown that, unlike other reported materials, the metastable high spin state is structurally identical to that reached as a result of the thermal spin transition. [Fe(L4)(_2)](BF(_4)) (_2)1/3H(_2)O is shown to have a fascinating complexity of spin crossover behaviour including the existence of a number of metastable states. The effect of dehydration on the spin crossover behaviour has been determined. Spin crossover compounds are extremely sensitive to changes in pressure; nonetheless there have been very few studies of the effect of pressure on the structure of these materials. The structure of the pressure induced low spin state at ambient temperature and 4.5 kbar is reported for [FeLl2](BF4)2. The crystallographic results are supported throughout by SQUID magnetometry studies.
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Kershaw, Cook Laurence Jonas. "Crystal engineering and bifunctionality in spin-crossover materials." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/7760/.
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This thesis focuses on crystal engineering metal salts of 2,2’:6’,2’’-terpyridine and 2,6-di(pyrazol-1’-yl)pyridine to tune and better understand the cooperative spin crossover in the solid state and incorporation of a second functionality towards bifunctional spin crossover materials. Chapter 1 can be considered an introduction to the phenomenon of spin crossover in first row transition metal complexes and outlines its discovery, recent developments and progression towards real-world application. Chaper 2 is a discussion of the methodology of synthetic efforts undertaken in the acquisition of the wealth of tris-chelating organic compounds whose coordination chemistry is the subject of later chapters. Chapter 3 details the spectroscopic, electrochemical and magnetic properties of cobalt(II) and iron(II) complexes of tris-azinyl analogues of 2,2’:6’,2’’-terpyridine in efforts towards tuning their electronic spin-equilibria. Chapter 4 presents a series of novel ruthenium(II) based materials exhibiting enhanced room temperature emission and their incorporation into an inert spin crossover host material. Retention of parent functionalities is screened for over an operable temperature regime. Chapter 5 concerns iron(II) complex salts of 2,6-di(pyrazol-1’-yl)pyridine derivatives, whose ligand backbones are modified in an attempt to tune the solid state spin crossover behaviour both electronically and sterically. Chapter 6 is an account of all synthetic procedures carried out during this work, their standard characterisation and details the instrumentation performed on all materials which are the subject of discussion in this thesis.
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Quintero, Pinzón Carlos Mario. "Luminescent spin crossover nanomaterials : physical properties and applications." Toulouse 3, 2012. http://thesesups.ups-tlse.fr/1899/.
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L'objectif principal de cette thèse est de fournir un nouveau protocole qui permet la détection de la transition de spin (TS) dans un nano-objet unique. Dans ce but, nous proposons d'utiliser la luminescence comme sonde très sensible qui peut être employée à des échelles où d'autres méthodes conventionnelles ne sont plus efficaces. Nous avons cherché à développer des nano-matériaux à TS avec des propriétés de luminescence dans le but d'isoler ces objets et ensuite sonder leurs propriétés via la détection luminescente. Sur la base de techniques de lithographie douce, plusieurs méthodes allant de l'assemblage aléatoire jusqu'à l'assemblage capillaire dirigé de nanoparticules à TS et également la synthèse in situ d'objets isolés luminescents à TS (ca. 150 nm) ont été explorées. Dans le même temps, leur étude en microscopie de fluorescence est présentée et les défis expérimentaux que cette tâche a imposée sont discutés. En outre, l'application potentielle de ces matériaux hybrides en microthermométrie est étudiée. Comme preuve de concept, des films minces de systèmes luminescents à TS ont été déposés sus des micro / nanofils chauffés par effet Joule afin de cartographier leur températureThe main objective of this thesis is to provide a new protocol that permits the detection of the spin crossover (SCO) phenomenon in a single nano-object. To accomplish this, we propose luminescence as a highly sensitive technique that may be employed at scales where other conventional methods are no longer effective. We aimed to develop SCO nano-materials with luminescence properties in order to isolate these objects, address them and then probe their properties via luminescent detection. Methods ranging from random to directed microcappilary assembly of SCO nanoparticles and also in situ synthesis of isolated luminescent SCO objects (ca. 150 nm) based on soft lithographic techniques were explored. At the same time, their investigation in fluorescence microscopy is shown and the experimental challenges that this task imposed are discussed. Also, the potential application of these hybrid materials in microthermometry is studied. As a proof of concept, thin films of luminescent SCO systems were employed to obtain thermal cartographies of gold micro - nanowires heated by Joule effect
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Huxel, Timo [Verfasser], and Julia [Akademischer Betreuer] Klingele. "Low-melting cationic transition metal complexes : : developing spin crossover ionic liquids = Niedrigschmelzende kationische Übergangsmetallkomplexe : die Entwicklung von Spin Crossover Ionic Liquids." Freiburg : Universität, 2014. http://d-nb.info/1123481598/34.
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Darawsheh, Mohanad D. "Spin crossover supramolecular coordination compounds: design, synthesis and properties." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/400859.
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The results obtained in this thesis demonstrate the importance of supramolecular chemistry for the design of potential new SCO clusters. Starting from synthesizing the suitable ligands with suitable functional groups, novel host-guest systems could be obtained where the guest play a major role in tuning the physical properties of the guest.
Two bis-pyrazolylpyridine lignads, H2L4 and H2L6 were designed and prepared to achieve the assembly of transition metal ions in a triple-stranded helicate fashion where the central cavity can encapsulate different counterions depending on the size of this cavity. The N-H groups found in these ligands which usually directed toward the internal cavity help in the encapsulation of hydrogen acceptor anions. 13 iron-based compounds have been crystallized and studied adding significantly to the helical SCO compounds in the literature. The crystal structure for all the compounds were resolved, which allowed for an extensive study of supramolecular interactions and the influence of these interactions on the magnetic properties of the compounds.
The first part of the thesis deals with spin-crossover dinuclear triple-stranded helicates compounds with encapsulated halide ions using H2L4. Six of such helicates with different encapsulated halide or counter ions were synthesized:
Cl⊂[Fe2(H2L4)3]Cl(PF6)2·5.7CH3OH (1)
Br⊂[Fe2(H2L4)3]Br(PF6)2·4CH3OH (2) Cl⊂[Fe2(H2L4)3]Cl(PF6)2·3CH3OH·1H2O (1a) Br⊂[Fe2(H2L4)3]Br(PF6)2·1CH3OH·1H2O (2a) Cl⊂[Fe2(H2L4)3](I3)3·3(Et2O) (3)
Br⊂[Fe2(H2L4)3](I3)3·3(Et2O) (4)
These isostructural compounds consist of triple-stranded helicates that encapsulate halide ion inside their cavity. The main difference is the kind of outer counterions and lattice solvents which affect dramatically the magnetic properties of these compounds as a result of changing the supramolecular interactions. Changing the halide ion from chloride to bromide in 1 and 2, respectively, shift the spin transition by 30 K. The SCO occur here from [HS-LS] to [HS-HS] upon heating.
Compounds 1a and 2a are the water solvate helicates that produced from single-crystal to single-crystal exchange by exposing the crystals to the ambient water. This exchange leads to important changes; the {X⊂ [Fe2(H2L4)3]}3+ helicate are now symmetric and the two Fe centers are crystallographically identical. This change in the solvent affects dramatically the SCO behavior of the helicates. Two-step SCO from [LS-LS] à [HS- LS]à [HS-HS] states was observed in the bulk magnetic studies. Compounds 3 and 4 consists of {X⊂ [Fe2(H2L4)3]}3+ triple-stranded helicates similar to the one seen in
previous helicates where the counter ions are now three triodide (I3-) linear ions
occupying the outer space formed between the helical strands and the solvent is ether. In these complexes the iron centers remain in the HS state through all the temperatures.
The change of the solvents used in the reaction yielded different supramolecular compounds using the same ligands H2L4. Dimerized mononuclear helicates
{X⊂[Fe(H2L4)3]2}3+ was prepared where a halide ion is encapsulated inside the cavity
formed by the intercalating dimers. Five dimerized triple-stranded helicates are presented in this thesis:
Cl⊂[Fe(H2L4)3]2(OH)(PF6)2·H2O (5).
Cl⊂[Fe(H2L4)3]2(FeCl4)3·2C3H6O·4C7H8 (6).
Br⊂[Fe(H2L4)3]2(OH)(PF6)2·H2O (7).
I⊂[Fe(H2L4)3]2(PF6)2.23(I)0.21(I3)0.56·2CH3OH (8)
I⊂[Fe(H2L4)3]2(I)2(I3)0.6(OH)0.4·0.6H2O·2CH3OH·2C3H6O (9)
In every mononuclear helicate, one pyrazolyl-pyridine side of each ligand is not coordinated to any metal ion. The SCO behavior of the dimer is also affected by the nature of the halide ions which make hydrogen bonding with the N-H groups of the pyrazole rings.
Using the ligand H2L6, the encapsulation of [M(III)(ox)3]3- (M = Fe and Cr; ox = oxalate) metal complexes inside the helical cavity of [Fe2(H2L6)3]4+ was achieved. Two of such triple-stranded helicates are presented in this thesis:
Fe(C2O4)3⊂[Fe2(H2L6)3](BF4)·4CH3OH·3.7H2O (10).
Cr(C2O4)3⊂[Fe2(H2L6)3](BF4)·1.4CH3OH·6H2O (11).
The Fe(II) ions of the helicate exhibit SCO behavior and LIESST effect in the case of the encapsulated chromium oxalate complex. Interestingly, the guest [Cr(III)(ox)3]3- exhibits SIM-like behavior at low temperatures. This is the first example where a host- guest system exhibits both LIESST effect and SIM behavior.Dos ligandos bis-pyrazolylpyridine, H2L4 y H2L6 fueron diseñados y preparados para sintetizar ensamblajes con iones de metales de transición en forma de helicatos de cadena triple donde la cavidad central puede encapsular diferentes contraiones en función del tamaño de esta cavidad. 13 compuestos a base de hierro se han cristalizado y estudiado, con la adición de manera significativa de compuestos helicoidales con SCO de la literatura. La estructura cristalina de todos los compuestos fueron resueltas, lo que permitió un amplio estudio de las interacciones supramoleculares y la influencia de estas interacciones sobre las propiedades magnéticas de los compuestos. La primera parte de la tesis trata de compuestos helicoidales dinucleares de cadena triple presentando transición de espín con iones haluro encapsulados utilizando H2L4. Estos compuestos isoestructurales consisten en helicatos de cadena triple que encapsulan iones haluro dentro de su cavidad. La principal diferencia es el tipo de contraiones exteriores y disolventes de cristalización que afectan dramáticamente las propiedades magnéticas de estos compuestos, como resultado de cambiar las interacciones supramoleculares. El cambio del ión haluro, de cloruro a bromuro, da un cambio de la transición de espín de unos 30 K. En los complejos metanólicos, la SCO se producen por calentamiento, a partir de [HS-LS] a [HS-HS], donde los estados de espín mixtos se consigue gracias a diferente distorsión alrededor de los iones metálicos, como resultado de diferentes enlaces de hidrógeno supramolecular cerca de los dos. Los helicatos con agua se producen a partir de una transformación cristal-cristal, mediante la exposición de los cristales a agua a temperatura ambiente. Este cambio en el disolvente afecta dramáticamente el comportamiento del SCO. Dos pasos en el SCO ([LS-LS] à [HS-LS] à [HS-HS]) se observarón en los estudios magnéticos. El cambio de los aniones a triyoduro (I3-) estabilizan el estado HS en todas las temperaturas medidas. El cambio en los disolventes utilizados en la reacción produjo diferentes compuestos supramoleculares utilizando el mismo ligando H2L4. Diferente helicatos mononucleares dimerizados {X⊂[Fe(H2L4)3]2}3+ fueron preparado donde se encapsula un ion haluro dentro de la cavidad formada por los dímeros intercalantes. En cada helicato mononuclear, un lado pirazolilo-piridina de cada ligando no se coordina a ningun ion metálico. El comportamiento de SCO del dímero también se ve afectada por la naturaleza de los iones haluro que forman con los enlaces de hidrógeno con los grupos N-H de los anillos de pirazol. Utilizando el ligando H2L6, se logró la encapsulación de complejos metálios de tipo [M(III)(ox)3]3- (M = Fe y Cr; ox = oxalato) dentro de la cavidad helicoidal [Fe2(H2L6)3]4+. Los iones Fe (II) del helicato exhiben SCO y efecto LIESST en el caso del complejo de cromo oxalato encapsulado. Curiosamente, el invitado [Cr(III)(ox)3]3- presenta un comportamiento de SIM a bajas temperaturas. Este es el primer ejemplo en el que un sistema hospedador-huésped exhibe tanto efecto LIESST y comportamiento SIM.
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Maldonado, Illescas María del Pilar. "Spin Crossover Phenomena: Towards Molecule-based Memories and Switches." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/444445.
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Avui en dia, la idea d'utilitzar molècules com a base de dispositius electrònics desperta molt d'interés en la comunitat científica arreu del món. La capacitat d'emmagatzemament d'informació des d'un punt de vista tecnològic creix a nivell exponencial i depén del desenvolupament en Nanociència. L'objectiu és l'emmagatzemament de dades ràpidament i amb miniaturització dels dispositius. Amb aquesta idea en ment, una de les estratègies més interessants està basada en el concepte de biestabilitat entre dos estats electrònics en una molècula, és a dir, anar d'un estat inicial (OFF) a un estat final (ON) sota la influència d'un estímul extern.
En la present tesi, per una banda, hem sintetitzat nous materials de transició d'espín aniònics amb lligams derivats de 1,2,4-triazol amb la intenció de ser una matèria primera en l'obtenció de materials funcionals, aconseguint així trímers amb transició d'espín per sobre temperatura ambient. A més a més, amb una TTIESST rècord en aquest tipus de compostos. També, per mitjà d'intercanvi catiònic hem aconseguit un nou compost amb propietats magnètiques diferents a l'original.
D'altra banda, hem estudiat diferents composites a partir d'un polímer conductor y compostos de transició d'espín, concretament trímers i polímers amb lligams derivats del 1,2,4-triazol, amb la finalitat de modificar les propietats elèctriques i termoelèctriques y generar una sinergia entre els comportaments magnètic i elèctric.Hoy en día, la idea de que una molécula pueda ser usada como base en un dispositivo electrónico despierta mucho interés en toda la comunidad científica en todo el mundo. La capacidad de almacenamiento de información desde un punto de vista tecnológico crece a nivel exponencial y depende del desarrollo en Nanociencia. El objetivo es el almacenamiento de datos rápidamente y con la miniaturización de los dispositivos y por ello, una de las más alentadoras estrategias está basada en el concepto de biestabilidad entre dos estados electrónicos en una molécula yendo de un estado inicial (OFF) a otro estado final (ON) bajo la influencia de un estímulo externo. En la presente tesis, por una parte, hemos sintetizado nuevos materiales de transición de espín aniónicos con ligandos derivados del 1,2,4-triazol con la intención de ser una materia prima en el empleo de materiales funcionales, obteniendo así trímeros con transición de espín por encima de temperatura ambiente y, además, con una TTIESST récord en este tipo de compuestos. Además, mediante el intercambio catiónico hemos logrado modificar sus propiedades magnéticas en base al compuesto original. Por otra parte, hemos estudiado diferentes composites a partir de un polímero conductor y compuestos de transición de espín, concretamente trímeros y polímeros con ligandos derivados del 1,2,4-triazol, con el fin de modificar las propiedades eléctricas y termoeléctricas y crear una sinergia entre comportamientos magnético y eléctrico.
Nowadays, the idea that molecules can be used as basis in an electronic device arouses scientific community around the World. The information storage capacity from technological demand a growing exponentially and depend on the development of Nanoscience. The aim is the storage of data quicker and the miniaturization of the devices and because of this, one of the most promising strategies is based on the concept of bistability between two electronic states of a molecule passing from an initial state (OFF) to a finale state (ON) under the influence of an external stimulus. In this thesis, on one hand, we synthetized successfully new anionic spin crossover materials with 1,2,4- triazole derivatives as coordinated ligand being used in multifunctional materials, obtaining trimers with spin transition above room temperature and in addition, with a record TTIESST in this kind of compounds. Moreover, with a cation exchange, we carried out to tune new compounds modifying theirs magnetic properties. On the other hand, we have studied several composites since a conductor polymer and spin transition compounds, specifically trimers and polymers with 1,2,4- triazole derivative ligands, with the purpose of modify the electrical and thermoelectric properties and create a synergy between the magnetic, electrical and thermoelectric behavior.
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Schlamp, Stephan [Verfasser], and Birgit [Akademischer Betreuer] Weber. "Amphiphilic Spin Crossover Complexes / Stephan Schlamp. Betreuer: Birgit Weber." Bayreuth : Universität Bayreuth, 2014. http://d-nb.info/106001002X/34.
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Bannwarth, Alexander [Verfasser]. "Photoswitchable Spin-Crossover Compounds for Surface Fixation / Alexander Bannwarth." Kiel : Universitätsbibliothek Kiel, 2011. http://d-nb.info/102016686X/34.
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Sung, Raymond Chi Wai. "ESR studies of some iron(II) spin crossover complexes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0013/NQ52415.pdf.
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Herold, Christian [Verfasser]. "Spin-Crossover Systems based on 1,3,4-Thiadiazoles / Christian Herold." Mainz : Universitätsbibliothek Mainz, 2019. http://d-nb.info/119418412X/34.
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Bovo, Gianluca. "Room temperature spin crossover in molecular and polymeric materials." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/51493.
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Spin crossover materials represent a remarkable model of molecular spin switching, where a transition between low spin and high spin configurations can be reversibly triggered by suitable external stimuli and is often accompanied by a hysteresis of various physical properties, holding potential for application in memory devices and optical switches. This thesis work investigates the thermal spin crossover behaviour of a class of Fe(II)-triazole polymers where the chemical properties can be tailored to achieve solubility in common solvents and one mononuclear Fe(II) complex deemed suitable for thermal evaporation. A broad spectrum of experimental techniques including magnetic, optical, calorimetric and structural assessments are applied to characterise the spin crossover phenomena in powders, thick films and pellets, highlighting the impact of the molecular environment and the effects of the processing methods on the spin switching. Additionally, thermal expansion measurements with a capacitance dilatometer provide a macroscopic evaluation of the mechanical changes associated with the transitions, which mirror the expansion/contraction of the Fe coordination sphere at the molecular level. Solution processing and vacuum deposition of the materials further enables the preparation and study of stable thin films, better suited to device application, with optical characterisation confirming the retention of spin crossover thermochromic properties. As a first step to deploy the iron-polymers inside simple electronic devices, MIM structures (metal-insulator-metal) are fabricated and tested by impedance spectroscopy, showing the presence of a thermal hysteresis loop in the dielectric function around room temperature. We demonstrate that in addition to the previous studies on bulk powders, optical and dielectric bistability with sharp spin transitions can also be achieved for thin films devices, thus opening interesting new perspectives for the application of spin crossover polymeric and molecular materials.
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Schlamp, Stephan Verfasser], and Birgit [Akademischer Betreuer] [Weber. "Amphiphilic Spin Crossover Complexes / Stephan Schlamp. Betreuer: Birgit Weber." Bayreuth : Universität Bayreuth, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:703-epub-1718-4.
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Bairagi, Kaushik. "Magnetic anisotropy and spin crossover at molecule-metal interfaces." Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCC241/document.
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L'utilisation de matériaux organiques pour l'électronique de spin suscite actuellement un fort intérêt. En effet, le long temps de diffusion de spin, la possibilité de manipuler l'état de spin d'une molécule ainsi que son interaction avec une surface magnétique offrent a priori de nouvelles possibilités pour la réalisation de nouveaux dispositifs d'électronique de spin. L'incorporation dans des dispositifs de molécules possédant deux états de spin nécessite la compréhension du phénomène de transition de spin une fois que les molécules sont en contact direct avec des surfaces métalliques.L'objectif de ce travail de thèse est l'étude des interfaces molécule-métal. Dans une première partie, nous avons étudié le magnétisme d'interfaces ferromagnétique-organique en utilisant différentes molécules et différents métaux ferromagnétiques. Nous nous sommes particulièrement intéresses a l'anisotropie magnétique dans ces systèmes. Dans une deuxième partie, nous avons étudié le phénomène de transition de spin moléculaire en contact avec une surface métallique. La spectroscopie d'absorption et le dichroïsme magnétique des rayons x ont d'abord permis de mettre en évidence cette transition à l'échelle globale ensuite, nous avons utilise la microscopie a effet tunnel pour étudier ce phénomène à l'échelle moléculaire dans un cristal 2d de molécule. Nous avons notamment observe la dynamique de la transition sous irradiation laser pour la première fois à l'échelle moléculaireThe use of organic materials in spintronic devices has recently raised a lot of interest. Large spin diffusion time in organic materials along with the flexibility of manipulating the spin state of the molecule and their interaction with the ferromagnetic metal electrode offers new functionalities in molecular spintronics. Understanding the spin crossover (sco) phenomenon for spin active molecules attached to metallic substrate is also necessary for a primary step towards device application.The main goal of the thesis work was to study these molecule—metal interfaces. In one part, we have studied the magnetism of the organic—ferromagnetic interface with different molecules and different ferromagnetic metals. The study was mainly focused on the magnetic anisotropy at the molecule-metal interfaces. In other part, we focused on the spin crossover phenomena of sco molecules attached to metallic substrates. X—ray absorption spectroscopy and magnetic circular dichroism techniques enabled us to study globally the spin crossover phenomenon. Using scanning tunneling microscopy we were able to study the sco phenomena at the single molecular level in a 2d crystal of molecules on a metal substrate. We have then studied locally the dynamics of the spin transition phenomenon upon laser exposure on a single 2d layer molecular crystal
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Hoefer, Andreas. "Vibrational spectroscopy on thermally and optically switchable spin crossover compounds." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=960457364.
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Bauer, Wolfgang [Verfasser], and Birgit [Akademischer Betreuer] Weber. "Understanding Spin Crossover : A Contribution / Wolfgang Bauer. Betreuer: Birgit Weber." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2011. http://d-nb.info/1015083749/34.
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Bornholdt, Claudia [Verfasser]. "Ligandgetriebener lichtinduzierter Spin-Crossover an Einzelmolekülen bei Raumtemperatur / Claudia Bornholdt." Kiel : Universitätsbibliothek Kiel, 2008. http://d-nb.info/1019809817/34.
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Mohammed, Rufeida. "Iron complexes of new dipyrazolylpyridine derivatives for spin-crossover applications." Thesis, University of Leeds, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.590300.
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This thesis concerns the synthesis and characterisation of new di(pyrazolyl)pyridine and di(pyrazolyl)pyrazine derivatives, and their iron(II) complexes which exhibit spin crossover behaviour. The examination of their magnetic behaviour using NMR spectroscopy, X-ray crystallography and magnetic measurements is described. Chapter One introduces the background behind the spin crossover phenomenon, especially in the case of iron(H) compounds. The methods of identification and the applications of spin crossover are discussed. Finally the aims of the research are also detailed. Chapters Two and Three discuss the synthesis and characterisation of previously unreported 2,6-di(4-R-pyrazol-I-yl)pyrazine compounds (R ~ CI, Br, I, Me, NO" NH" CCPh). The synthesis of their iron(ll) complexes as BF, and CIO, salts is also detailed, and their magnetic behaviour is discussed and compared to previous 2,6- bis(pyrazol-l-yl)pyridine complexes. The crystal structures of the complexes are presented. Chapter Four is a study of novel di(pyrazol-l-yl)pyridine derivatives substituted at the pyrazolyl or pyridyl 4-positions, and their iron(Il) complexes as before. Magnetochemical data for three complexes are presented, together with crystallographic data and a discussion relating structure to magnetic behaviour. Chapter Five focuses on the study of di(pyrazolyl)pyridine derivatives substituted at the pyridyl 4-positions by azo, ethynyl or styryl groups, and their iron(ll) complexes. Examination of their magnetic behaviour and crystal structures demonstrates the difficulty of predicting the spin state of an iron(lI) complex.
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Pritchard, Ruth. "Studies of Iron (II) and Iron (III) spin crossover compounds." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487772.
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Bertoni, Roman. "Ultrafast photo-switching of spin crossover crystals : coherence and cooperativity." Phd thesis, Université Rennes 1, 2013. http://tel.archives-ouvertes.fr/tel-01016162.
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The main topic of this thesis is the study of the ultrafast photo-switching of photo-magnetic molecular materials showing transition between spin states. These molecular crystals are prototypes of molecular bistability between two distinct electronic states, HS and LS. The molecules can be switched between these two states by a light pulse. The emergence of ultrafast techniques allows us to study in real time these photo-switching processes and also the associated out-of-equilibrium dynamics down to the femtosecond scale (10-15s). We have combined probes sensitive to the change of electronic state, on the hand, and to structural rearrangements, on the other hand, in order to observe these photo-switching processes. The measurements of ultrafast transient absorption spectroscopy have been made using the laser plateform at the IPR. Complementary time resolved X-ray diffraction and absorption experiments have been performed on large facilities. The first part of this manuscript is focused on the photo-switching dynamics at molecular scale. It reveals a complicated interaction between electronic and structural degrees of freedom. The generation and damping of coherent optical phonons is identified as a key parameter in the trapping in HS potential. Several experiments on different compounds show the linear and local character of such ultrafast photo-switching. The second part of this thesis presents studies on the complete out of equilibrium dynamics. It reveals a cascading process with activation of elastic and thermal effects at different time scales. Cooperative processes following a light excitation are observed. These complexes dynamics are driven by propagating and diffusive process sensitive to the size of the sample. The study of nanocrystals yields high conversion and faster response to elastics effect than single-crystals. These studies further elucidate the out of equilibrium processes underlying the photo-induced phase transitions on time and length scales, from the molecule to material scale.
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Elhaik, JeÌroÌ‚me Ange. "Iron (II) spin crossover complexes of dipyrazolylpyridine and related ligands." Thesis, University of Leeds, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414161.
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Powell, Robyn. "Structures and magnetic properties of iron(III) spin-crossover compounds." Thesis, Aston University, 2017. http://publications.aston.ac.uk/37512/.
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Transition metal fragments displaying switching behaviour are appealing materials, which may be used in a functional way in research and technology. Some molecular species containing transitionmetal ions may exhibit a crossover between states having a different magnetic moment, the magnetic interconversion between the low-spin and high-spin state in FeIII systems which can be triggered by a change in temperature, pressure or by light irradiation. The research presented in this thesis focuses on using substituted derivatives of R-salicylaldehyde 4R’-thiosemicarbazone (H2L, H2-R-thsa-R’) for generating FeIII spin crossover. The aim was to design mononuclear FeIII compounds with a view of studying their structural features and magnetic properties. The results present the full structural analysis of differently charged FeIII-bis(ligand) complexes, these include: (i) (cation+)[FeIII(L2‒)2]·x(solvent), (ii) [FeIII(HL‒)(L2‒)]·x(solvent) and(iii) [FeIII(HL‒)2](anion‒)·x(solvent). The studies discuss several influences on the structural features and the magnetic properties of the reported FeIII compounds, these include: the nature of the anionor cation associated with the FeIII complex, the degree of solvation of the complex and the variations in the ligand substituents. The magnetic studies of the (cation+)[FeIII(L2‒)2]·x(solvent) compounds have presented one high-spin compound ((CH3)2NH2[Fe(3-OEt-thsa)2]) and four low-spin compounds (Cs[Fe(3-OEt-thsa-Me)2]·CH3OH, Cs[Fe(5-Br-thsa)2], NH4[Fe(thsa)2] and NH4[Fe(5-Br-thsa)2]), of which NH4[Fe(5-Br-thsa)2] revealed a fraction of the FeIII ions convert into the high-spin state. Three [FeIII(HL‒)(L2‒)]·x(solvent) compounds have been studied, of which a rare two-step spin transition has been observed for [Fe(H-5-Cl-thsa-Me)(5-Cl-thsa-Me)]·H2O, while the isostructural compounds [Fe(Hthsa-Me)(thsa-Me)]·H2O undergoes an incomplete spin transition and [Fe(H-3-OEt-thsa-Me)(3-OEt-thsa-Me)]·H2O remains in the high-spin state. It was recognised that the steric and electronic features imposed by the R,R’-substituents may have an impact on the spin state of FeIII cations, and affect at which temperature the spin transition occurs. Furthermore, the FeIII cation of both [FeIII(HL‒)2](anion‒)·x(solvent) compounds, [Fe(H-5-Br-thsa-Et)2](NO3)·H2O and [Fe(H-4-OHthsa)2]4·(SO4)2·9H2O, were found to be in the high-spin state. Collectively, the described research has provided new insight into this family of FeIII bis(Rsalicylaldehyde4R’-thiosemicarbazone) compounds and provides a strong foundation for further studies.
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Nieto, Castro David. "Advances in Spin Crossover: Synthesis, Mechanosynthesis and Switchable Multifunctional Hybrids." Doctoral thesis, Universitat Rovira i Virgili, 2021. http://hdl.handle.net/10803/673157.
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Els compostos d' "spin crossover" (SCO) són materials moleculars formats per ions metàl·lics amb configuració electrònica d4d7 i lligands que desdoblen els orbitals d . Aquests materials presenten propietats rellevants per aplicacions pràctiques, ja que són capaços de produir una transició d' spin mitjançant un estímul extern, com per exemple, un canvi a la temperatura o la pressió, irradiació amb llum o mitjançant l'aplicació d'un camp magnètic. Fins ara, diferents complexes de coordinació amb distints centres metàl·lics han estat sintetitzats. Dins d'aquesta gran varietat de compostos, els que tenen un centre actiu Fe(II) han estat els més estudiats ja que, en alguns casos, la transició d' spin ocorre prop de la temperatura ambient, de forma abrupta, amb histèresi i amb gran estabilitat durant els successius cicles. Aquestes característiques fan que els compostos de SCO basats en Fe(II) tinguen rellevància per aplicacions pràctiques en electrònica molecular, dispositius per emmagatzematge d'informació, pantalles electròniques o actuadors.A la present tesi doctoral s'han desenvolupat diferents estratègies dins del camp de SCOLos compuestos de “Spin crossover” (SCO) son materiales moleculares formados por iones metálicos con configuración electrónica d4d7 y ligandos que desdoblan los orbitales d. Dichos materiales poseen propiedades relevantes para aplicaciones prácticas, ya que son capaces de producir una transición de spin mediante un estímulo externo, como por ejemplo, un cambios en la temperatura o presión, irradiación de luz o mediante la aplicación de un campo magnético. Hasta la fecha, diferentes complejos de coordinación con distintos centros metálicos activos en SCO han sido sintetizados. Dentro de esta gran variedad de compuestos, los que tienen como centro activo Fe(II) han sido los mas estudiados ya que, en algunos casos, la transición de spin ocurre cerca de la temperatura ambiente, de forma abrupta, con histéresis y con gran estabilidad durante sucesivos ciclos. Estas características hacen que los compuestos de SCO basados en Fe(II) tengan relevancia para aplicaciones prácticas en electrónica molecular, dispositivos para almacenamiento de información, pantallas electrónicas o actuadores.En la presente tesis doctoral, se han desarrollado distintas estrategias dentro del campo de SCO.
Spin crossover (SCO) complexes are molecular materials with d4 d7 metal ions that possess a set of properties relevant for practical applications, since they are able to display a spin transition in response to external perturbation, such as a change of temperature, pressure, light irradiation or pulsed magnetic field. To date, many coordination SCO complexes have been studied with different metallic SCO active centres. Among the diverse variety of metal ions, Fe(II) has been the most studied one as, in some cases, the spin transition occurs abruptly, with hysteresis, close to room temperature and is stable over successive cycles. These features make Fe(II) SCO complexes suitable for relevant practical applications in molecular electronics, data storage, display devices, non-linear optics, and photomagnetism. In the present doctoral thesis, several approaches in the field of SCO have been performed.
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Ould, Moussa Nawel. "Photomagnetic properties of spin crossover complexes with multi-metastable states." Toulouse 3, 2007. http://www.theses.fr/2007TOU30036.
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Ce travail de thèse a pour objectif principal l'étude des propriétés de photo-commutation dans le visible et l'infrarouge de composés moléculaires à transition de spin. Les systèmes étudiés ont la particularité de présenter plusieurs états métastables à basse température : "Composés à transition de spin multi-métastables". L'enjeu actuel de tels systèmes ainsi que les processus de photo-commutation est de taille dans le domaine de l'adressage optique de l'information. Afin d'effectuer cette étude, nous avons choisi cinq composés chimiquement distincts : un mononucléaire, [Fe(ptz)6](BF4)2 (ptz = 1-propyltetrazole), pour lequel on a mis en évidence le découplage entre la transition cristallographique et la transition de spin photo-induite et quatre binucléaires de la famille {[Fe(L)(NCX)2]2bpym} (X = S ou Se; L = bpym (2,2'-bipyrimidine) ou bt (2,2'-bithiazoline)), où nous avons pu montrer entre autre qu'il est possible de convertir l'état fondamental bas spin de façon sélective en deux états macroscopiques distincts en fonction de la longueur d'onde de l'éclairement utilisé (visible ou infrarouge)The aim of the present work was to develop a detailed picture of the photo-excitation process in some special spin crossover complexes, which exhibit more than one long-lived metastable states. We are interested in the effects of visible and infrared light irradiation on these systems. Such “multi-metastable spin crossover complexes” display actually an interesting and largely unexplored photophysics and hold also some promises as future candidates for storing and transferring information in molecular devices. In order to explore this topic, we have chosen five different systems: the mononuclear [Fe(ptz)6](BF4)2 complex (ptz = 1-propyleterazole) for which we demonstrate a clear decoupling between the crystallographic phase transition and the light-induced spin conversion and four binuclear complexes of the family {[Fe(L)(NCX)2]2bpym} (X = S or Se; L = bpym (2,2'-bipyrimidine) or bt (2,2'-bithiazoline)). This last study led to a number of original results, revealing for example wavelength-selective photomagnetic phenomena in these systems
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Clements, John Edward. "Spin crossover and postsynthetic modification in nanoporous Hofmann-type materials." Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/13714.
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Herein, the Hofmann-type spin crossover (SCO) material [Fe(bipytz)(Au(CN)2)2].xEtOH (1•EtOH) where bipytz = 3,6-bis(4-pyridyl)-1,2,4,5-tetrazine and its covalent postsynthetic modification (PSM) is described. In the first instance, structural characteristics of the as-synthesised phase 1•EtOH are investigated by variable temperature single-crystal X-ray diffraction, with follow-up SCO analysis performed with a mixture of variable temperature magnetic susceptibility, solid-state diffuse reflectance, lab- and synchroton-sourced powder X-ray diffraction. The influence of guest-exchange on 1•EtOH was also investigated, including the guest-free phase. Significant influences on the structure emerged from C–H…N and aurophilic interactions between the two-fold interpenetrated nets. Once 1•EtOH is fully described, a pre-functionalised ligand derivative 3,6-bis(4-pyridyl)-1,2,-diazine (bipydz) is used to synthesise a related Hofmann-type phase [Fe(bipydz)(Au(CN)2)2].xEtOH (2•EtOH). Similar investigation methods used for 1•EtOH are employed and reveal the first porous four-step spin crossover material, with each state identified as: HS1LS0, HS0.67LS0.33, HS0.5LS0.5, HS0.33LS0.67 and HS0LS1. Unlike 1•EtOH, 2•EtOH shows markedly different properties: it does not display negative thermal expansion, the SCO transition is nearly 100 K lower in temperature, the solvent is ordered within the pores, the chromic behaviour is drastically altered and the LIESST and reverse-LIESST effects are now observed – all from replacing two N atoms with C–H bonds. An analogous material obtained from PSM with 2,5-norbornadiene is also described, as well as phases generated from reaction with ethylene gas and pyrrole. These materials have a vastly different structural-magnetic phase transitions to 2•EtOH, with several interesting structure-function relationships established from the investigations, giving unprecedented insight into the influence of PSM on SCO.
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Mouri, Shinichiro. "Dynamical properties of photo-induced spin conversion in the spin crossover complex with multi-stability." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/124406.
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Archer, Rosanna Juliet. "The Effects of Supramolecular Interactions on Iron(II) Spin Crossover Compounds." Thesis, University of Canterbury. Chemistry, 2013. http://hdl.handle.net/10092/9053.
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Molecules with functional properties, especially ones that display spin crossover behaviour, are becoming increasingly well researched due to their potential applications as the active components in molecular memory, optical displays or sensors.1,2 To this end, a series of Fe(II) coordination compounds utilising imidazolylimine and pyridylimine based ligands have been synthesised and their spin crossover behaviour analysed through a variety of techniques including variable temperature X-ray crystallography, magnetic susceptibility, surface reflectivity and UV-Visible spectroscopy. Light-Induced Excited Spin-State Trapping (LIESST) effects have also been analysed via photomagnetic measurements.
Particular attention was paid to the supramolecular interactions present within the
solid-state and the effect that these interactions may have on spin crossover behaviour. Subtle changes to the complexes through counter-anion exchange, solvent effects and ligand design were explored and careful structural analysis completed.
This study was separated into two distinct categories. The first describes the synthesis, structural characterisation and spin crossover behaviour of Fe(II) dinuclear triple helicates. Four dinuclear triple helicates have been synthesised, three of which display spin crossover behaviour. Weak LIESST effects were observed in two of these examples. Variation in the ligand field strength between the complexes was achieved through modification of the coordinating “head group” and differences between the flexibility of the ligand backbone were also explored.
The latter part of this study describes the synthesis, structural characterisation and spin crossover behaviour of novel Fe(II) mononuclear complexes. A series of related ligands which differ in the p-substituent have been synthesised and their coordination chemistry with Fe(II) metal ions examined. Subtle changes to the counter-anion and crystallised solvent molecules were also explored during this study. Five mononuclear Fe(II) complexes were shown to undergo spin crossover and the structural changes associated with the spin-state conversion have been analysed via variable temperature X-ray crystallography and compared with magnetic susceptibility measurements. Two complexes were also analysed for LIESST behaviour and these complexes showed full photo-excitation into the high-spin state at 10 K.
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Pukenas, Laurynas. "Fabrication and characterisation of SAMs for spin crossover and photocleavable surfaces." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/16602/.
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This thesis investigates self-assembled monolayers (SAMs) of molecules of various complexity with a special focus on fabrication of surfaces that could exhibit an intrinsic active function, more precisely a capability to switch between two stable states upon external stimuli (spin crossover phenomenon) or to expose functional groups upon irradiation with light, i.e. photocleavage of a SAM. SAM formation of a complex novel molecule, lipoic acid ester of α-hydroxy-1-acetyl-pyrene (reagent 1), was studied in chapter 3. It contains i) a dithiolane headgroup capable of binding to gold surfaces via two sulfur atoms, and ii) a chromophore that makes it light sensitive (photocleavable) and leads to a deprotection of lipoic acid molecule upon exposure to soft UV (365nm). Reagent 1 successfully forms SAM1, but it interacts with the gold surface weaker than conventional thiol based SAMs, due to cross-linking of dithiolane headgroups. Nevertheless, SAM1 is a relatively stable monolayer and exerts a higher barrier against diffusion of copper ions towards gold surface in electrochemical deposition than SAMs of similarly complex molecules but with thiol headgroups or shorter alkanethiol SAMs terminated with carboxylic acid groups (COOH). SAM1 undergoes photolysis upon soft UV (365nm) irradiation, but only in the acidic catalyst 100mM HCl in isopropanol (IPA). Unexpectedly, this also leads to a removal of the resulting lipoic acid monolayer, thus ultimately leading to SAM1 with lower surface coverage, and changes packing and ordering. SAMs of alkanethiols terminated with COOH and of varying chain length were investigated in order to better understand the cause for the instability of lipoic acid monolayer. Loss of molecules from the surfaces was found to be a common issue in the COOH SAMs, however, the severity of the loss is strongly related to the initial SAM thickness. Thin SAMs like DTBA SAM yield huge (∼50%) loss, while thick SAMs like MUA SAM show no detectable loss. On the other hand, photo-patterned SAM1 produces especially high selectivity of Cu deposition between UV treated and non-treated regions, which is associated to this loss of surface coverage, packing and ordering. Surprisingly, reagent 1 also interacts with glass and silicon oxide surfaces to form hydrophobic films that exhibit green fluorescence under soft UV light. Such surfaces are photo-sensitive and can be photo-patterned in the air or in the acidic catalyst to produce non-fluorescent hydrophilic regions due to photo-bleaching of pyrene groups and photo-deprotection of lipoic acid molecules, respectively. The films and patterns stored under ambient conditions are detectable for at least 35 days. Formation of those films is associated with an interaction of pyrene group with adsorbates on the surfaces, while film growth is attributed to the cross-linking of dithiolane headgroups. SAM fabrication of metal complexes was explored in chapter 4. Two novel ligands L1 and L2, and their corresponding Fe(II) complexes C1 and C2, which can exhibit spin crossover (SCO) behaviour in bulk, were investigated. Both ligands successfully form SAMs. However, SAM L1 does not coordinate Fe(II), while its preformed complex C1 is not stable on Au surface and forms SAM L1 instead of SAM C1. In contrast, SAM L2 coordinates Fe(II) at nearly 100% yield, which leads to almost the same chemical composition as in a SAM of its preformed Fe(II) complex C2 (SAM C2). Although complex C2 with MeCN as the sixth exogenous ligand (SEL) exhibits low spin (LS) state in bulk at room temperature, only high spin (HS) state was detected in SAM C2. Complex C2 exhibits a unique property of changing its spins state in certain solvents, because a solvent molecule can easily displace the sixth exogenous ligand (SEL). However, rinsing SAM C2 with such solvents did not lead to a spin transition, and LS state was never observed for the SAM. This implies that the strength of the ligand field may need to be increased or SEL with a higher affinity coordinated to complex C2, in order to change the spin state by rinsing or to detect SCO in SAM C2. A long-chain alkanethiololigoethyleneglycol (LCAT-OEG) type molecule terminated with the azide group (reagent 2) was investigated for the facilitation of click chemistry on gold surfaces (chapter 5). Reagent 2 forms a good quality SAM (SAM2), and the concentration of reagent 2 in the SAM can be reduced in a controlled and predictable manner by the addition of LCAT-OEG-1 or LCAT-OEG-4 to the growth solution. QCMD measurements indicate that the whole surface of SAM2 successfully undergoes click reaction with cycloalkyne in aqueous solution without any catalyst. Finally, simple alkanethiol and aromatic type SAMs were investigated for use in surface-enhanced Raman spectroscopy (SERS) with nanoparticle-on-mirror configuration and for studying plasmonic systems, due to their ability to yield optimum precision over the control of thickness and dielectric function (chapter 5).
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Daniell, Joanna. "Synthesis and characterisation of new spin crossover salts and molecular magnets." Thesis, University of Surrey, 2016. http://epubs.surrey.ac.uk/810422/.
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This research focuses on the synthesis and characterisation of novel molecular salts with the potential to undergo spin crossover (SCO) transitions. SCO describes the reversible transition between the LS and HS states, which can occur in some first row transition metal complexes with d4 – d7 valence electrons, induced by changes in external stimuli such as temperature. The rearrangement of electrons during the SCO transition results in changes to the properties exhibited by the bulk material, which can be characterised by a number of methods. Such techniques used in this work include X-ray diffraction (XRD), SQUID (Superconducting Quantum Interference Device) magnetisation measurements, differential scanning calorimetry (DSC) and Mössbauer spectroscopy. Both cationic and anionic complexes of iron (II) and iron (III) have been synthesised with a range of ligands, based on 2,6-bis(pyrazol-1-yl)pyridines/pyrazines (dpp), salicylaldehyde triethylenetetramine (sal2-trien) and salicylaldehyde thiosemicarbazones (thsa). Ionic materials previously reported to exhibit molecular conductivity are used as counterions, such as tetrathiafulvalene (TTF+), 7,7,8,8-tetracyanoquinodeimethane (TCNQ-), nickel (II) complexes of maleonitriledithiolate ([Ni(mnt)2]-) and 2-thioxo-1,3-dithiole-4,5-dithiolato ([Ni(dmit)2]-). Metathesis reactions or electrocrystallisation experiments have been utilised, resulting in salts in one of the following combinations; [SCO]+[Conductor]- or [Conductor]+[SCO]- where SCO is a potential SCO metal complex and conductor is an ion which may support electrical conductivity. Whilst there are a limited number of examples of the former, no examples have been found of the latter combination. The synthesis of SCO double salts has also been attempted to give [SCO][SCO] compounds, by reacting cationic iron (II) complexes with dpp ligands with anionic iron (III) complexes with thsa ligands. All products have been analysed by a range of techniques, including elemental analysis, infra-red spectroscopy, XRD, DSC, SQUID magnetisation measurements, Mössbauer spectroscopy and variable temperature resistance measurements. A number of novel products have been synthesised and characterised, some of which exhibit interesting behaviours ranging from SCO transitions to semiconductivity to long range magnetic order. Iron (II) complexes with dpp-type ligands exhibited a range of SCO behaviours (hysteretic, abrupt, gradual) depending on the anion. A combination of iron (III) complexes with sal2-trien derivative ligands yielded both ferro- and ferrimagnetic compounds. It was determined that minor structural changes via halogen substitutions (Cl or Br) can change the nature of magnetic ordering. The presence of both iron (II) and iron (III) centres in the SCO double salts resulted in multiple SCO transitions.
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Shen, Yuwei. "Metal-Organic Frameworks - Spin Crossover Complexes Hybrid Architectures for VOCs Sensing." Electronic Thesis or Diss., Université Paris sciences et lettres, 2022. http://www.theses.fr/2022UPSLS038.
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Chapitre I :La première partie de ce chapitre est consacrée à une introduction générale sur les COVs, y compris leurs sources d'émission, le risque sanitaire lié à l'exposition à ces composés et l'état de l'art des techniques actuelles de détection des COVs. La deuxième partie explique les bases du phénomène de transition de spin avec une attention particulière sur la transition de spin induite par adsorption de vapeurs. La troisième partie est consacrée à une brève description des MOFs, de leurs propriétés générales et des stratégies de synthèse classiques. Enfin, la quatrième partie est composée d'une revue des progrès récents des capteurs optiques à base de MOFs pour la détection des COVs.Chapitre II :Ce chapitre concerne la conception de matériaux poreux bistables basés sur l'imprégnation d'un complexe de FeIII à transition de spin (SCO) dans un MOF chimiquement robuste (MOF-808-Zr), dénommés SCO⊂MOF. Il présente la synthèse de composés hybrides avec quantité de complexe contrôlée, l'étude de leurs propriétés de commutation et de l'origine d'une telle bistabilité avec l’aide de simulations moléculaires. Des résultats supplémentaires relatifs à l'impact de la fonctionnalisation du complexe de FeIII à transition de spin sur les propriétés de commutation des composés hybrides, ainsi que sur le processus de mise en forme des composés sont également détaillés dans ce chapitre.Chapitre III :Ce chapitre présente l'impact de la topologie du MOF sur les propriétés de commutation du matériau SCO⊂MOF. Les complexes de FeIII étudiés au Chapitre 2 sont insérés dans un MOF mésoporeux robustes à base de Zr, le MIP-206. Différentes stratégies de synthèse de ce MOF sont testées afin de contrôler la taille des particules. La fabrication de films minces SCO⊂MOF est enfin décrite.Chapitre IV :Dans ce dernier chapitre, les capacités de détection de certains COVs des films minces poreux commutables développés dans les chapitres 2 et 3 sont évaluées. L'influence des propriétés des films minces sur les performances de détection est également étudiée.Enfin, la conclusion générale et les perspectives associées à ces travaux sont discutées. En résumé, ce projet décrit une nouvelle stratégie pour construire des matériaux poreux commutables basés sur des complexes de FeIII à transition de spin et différents MOFs à base de Zr(IV). Les solides présentent des propriétés de commutation prometteuses. La fabrication d'un film mince optiquement actif en utilisant ces matériaux a été développée et par la suite, leurs capacités de détection ont également été évaluées et optimiséesChapter I:The first part of this chapter is dedicated to a general introduction of VOCs including their emission sources, the exposure-related health risk and the state of the art of current VOC sensing techniques. The second part explains the basics of the spin-crossover phenomenon with a special focus on the guest-induced spin crossover. The third part is devoted to a brief description of MOFs featuring their general properties and typical synthetic strategies. Lastly, the fourth section is composed of a review stating the recent progress in MOF-based optical sensors for VOCs sensing.Chapter II:This chapter involves the design of porous materials with magnetic bistability based on the impregnation of a FeIII SCO complex into a chemically robust MOF (MOF-808-Zr), denoted as SCO⊂MOF. This work contains the synthesis of the hybrid compounds with tunable SCO loading, the investigation of their switching properties and of the origin of such bistability through the perspective of molecular simulations. Additional results relating to the impact of the functionalization of the FeIII spin crossover (SCO) complex on the switching properties of the hybrid compounds, as well as the shaping process of the compounds are also detailed in this chapter.Chapter III:This chapter presents the impact of MOF topology on the switching properties of the SCO⊂MOF material. The same series of the FeIII complexes is inserted into robust Zr-based MOFs (MIP-206s). Different synthetic strategies are tested for this MOF in order to regulate its particle size. The SCO⊂MOF thin film fabrication also is finally described.Chapter IV:In the last chapter, the sensing capacities for certain VOCs of the porous switchable thin films developed in Chapters II and III are evaluated. The influence of the properties of thin films on the sensing performance is also studied.In the end, the general conclusion and perspectives are discussed. In summary, this project describes a novel strategy to construct porous switchable material based on FeIII SCO complexes and different Zr(IV)-based MOFs. The solids display promising switching properties. Fabrication of optical-active thin film using these materials has been achieved, and subsequently, their sensing capacities have also been evaluated and optimized
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Gonzalez, Estefan Juan Héctor. "Microfluidic synthesis of switchable materials." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0199.
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La méthodologie classique pour la synthèse de matériaux à transition de spin a un certain degré d’irréproductibilité du fait de l’imprévisibilité des flux turbulents à l’intérieur du milieu réactionnel contenu dans la verrerie ordinaire de laboratoire. Pour tenter de résoudre ce problème, nous explorons la microfluidique de gouttelettes sans tensioactifs comme une nouvelle méthode d’obtention de matériaux à transition de spin.Après avoir testé divers dispositifs microfluidiques, nous avons synthétisé le MOF de type Hofmann [Fe(pz)Pt(CN)4] en combinant deux solutions de réactifs dans un canal débouchant immédiatement dans une buse de focalisation de flux. Le produit obtenu présente une réduction drastique de la taille de particule par rapport aux méthodes classiques, et affiche un comportement magnétique consistent avec les nanoparticules rapportées antérieurement.Malheureusement, du fait des hautes concentrations utilisées ici, la réaction se produit très rapidement, et le dispositif peut facilement se boucher si les flux sont modifiés ou perturbés. Pour résoudre ce problème, nous avons développé une nouvelle méthode : une substance causant un gonflement du PDMS est mélangée avec l’huile de la phase continue pour obtenir une réduction des dimensions du dispositive, et ainsi réduire le diamètre des gouttes de presque deux ordres de grandeurThe conventional methodology to synthesize spin-crossover materials has some degree of irreproducibility due to the unpredictability of the turbulent flows in the reaction media contained in ordinary laboratory glassware. To address this issue, we explore surfactant-free droplet microfluidics as a new method to synthesize spin-crossover materials.After probing the use of different microfluidic devices, we synthesized the Hofmann type MOF [Fe(pz)Pt(CN)4] by combining two solutions with reactants into a channel that immediately reaches a flow-focusing junction. The product obtained displays a strong decrease in its particle size compared with the batch synthesis. The obtained nanoparticles display a magnetic behavior consistent with the nanoparticles reported previously.Unfortunately, under the high concentrations used here, the reaction occurs very quickly, and the device can easily clog when the flow rates are changed. This leads to difficulties when attempting to modulate the dimensions of the droplets without affecting the general performance of the device. To solve this problem, we developed a new method where a swelling agent is combined with the oil used as the continuous phase, resulting in a change in the critical dimensions of the PDMS chip and a change of the diameter of the droplets of almost two orders of magnitude
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Kaase, Dominic [Verfasser], and Julia [Akademischer Betreuer] Klingele. "Designing chalcadiazoles and triazolopyridines for the construction of oligo- and polynuclear spin crossover compounds = Gestaltung von Chalkadiazolen und Triazolopyridinen zur Konstruktion von Oligo- und Polynuklearen Spin Crossover Verbindungen." Freiburg : Universität, 2014. http://d-nb.info/112348161X/34.
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Djomgoue, Paul. "N3, N4/(N3S, N3O) and N6 Phenanthroline Bases and their Spin Crossover Iron(II) Complexes." Doctoral thesis, Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-207498.
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The present dissertation focuses on the synthesis of iron(II) complexes and the study of their SCO behavior. The equilibrium between the HS and the LS states gives to the SCO systems large potential applications for molecular electronics. However, today there is not a single molecular device from SCO compounds in the market. This is due to the fact that the SCO systems discovered up to now were unable (e.g. TLIESST « 300 K) for these applications. The aim of this thesis is to synthesize new SCO compounds with sustainable properties for applications. In the beginning of the thesis, [Fe(rac-22a))]2+∙2[BF4]- and [Fe(rac-22b)]2+∙2[BF4]- employing rigid hexadentate ligands were described. In contrast to the expectation, the N-methylation of the amines shifts the equilibrium towards the LS state. [Fe(rac-22b)2+∙2[BF4]- shows a T1/2 higher at 74 K and 52 K than the non methylated [Fe(rac-22a)2+∙2[BF4]- respectively in nitrobenzene and acetonitrile. The T1/2 are solvent-dependent for these complexes. After that, ligand series 9-R2-2-(6-R1-pyridin-2-yl)-1,10-phenanthroline 25b (R2 = Me), 25f (R2 = Ph), 25d (R2 = C(O)H), 25c (R1 = Ph), 25l (R1 = oxylphenyl-4-oxymethylene), 25m (R1 = oxymesitylene) and 25j (R1 = pyrol-1-yl) were synthesized. It was observed that the size of the substituent influences the SCO properties (T1/2). In addition, the influence of the counterion was shown with [Fe(25c)2]2+∙2[BF4]- and [Fe(25c)2]2+∙2[B(Ph)4]-. The B(Ph)4- conterions bring π∙∙∙π interactions in the molecular cell which shift the T1/2 parameter to a high temperature (200 K) compared to the complex with BF4- ions (175 K). Moreover the substituents R1 on the terminal position of the pyridine effect on T1/2 more than the substituents R2 on the terminal position of the phenanthroline. For example, [Fe(25f)]2+∙2[BF4]- (R1 = Ph) is a pure HS complex while the complex [Fe(25c)]2+∙2[BF4]- (R2 = Ph) is a SCO system (T1/2 = 175 K). The expansion of the coordination mode from N6 to N8 was investigated by the synthesis of the tetradentate ligands. This expansion shows an unexpected coordination mode, [Fe(25i)2]2+∙2[BF4]- (R2 = pyrazol-1-yl) forms a distorted square antiprism coordination geometry (HS iron(II)-complex) and does not show any Fe-N bond breaking over the application of the temperature as expectedDie vorliegende Dissertation behandelt die Synthese von Eisen(II)-Komplexen und ihr spin crossover (SCO)-Verhalten. Das Gleichgewicht zwischen high-spin (HS)- und low-spin (LS)-Zustand verleiht den SCO-Systemen eine großes Anwendungspotential im Bereich der molekularen Elektronik. Dennoch existiert bis heute kein SCO-basiertes molekulares Bauteil auf dem Markt. Hauptgrund hierfür ist, dass die bislang bekannten SCO-Systeme keine hinreichenden Eigenschaften (z.B. TLIESST « 300 K) aufweisen. Das Ziel der vorliegenden Arbeit ist die Synthese neuer SCO-Verbindungen mit geeigneten Eigenschaften für die Anwendung. Zu Beginn der Arbeit werden die Komplexe [Fe(rac-22a)]2+∙2[BF4]– und [Fe(rac-22b)]2+ ∙2[BF4]– mit starren hexadentaten Liganden beschrieben. Entgegen der Erwartung verschiebt die N-Methylierung der Amine das Gleichgewicht in Richtung des LS-Zustandes. Verglichen mit dem nicht-methylierten Komplex Fe(rac-22b)]2+∙2[BF4]– zeigt Fe(rac-22a)]2+∙2[BF4]– eine höhere Übergangstemperatur T1/2, welche in Nitrobenzen 74 K und in Acetonitril 52 K beträgt. Für die Komplexe ist T1/2 lösungsmittelabhängig. Im Folgenden wurde die Ligandenserie 9-R2-2-(6-R1-pyridin-2-yl)-1,10-phenanthrolin mit den Vertretern 25b (R2= Me), 25f (R2 = Ph), 25d (R2 = C(O)H, 25c (R1 = Ph), 25l (R1 = oxyphenyl-4-oxymethylen), 25m (R1 = oxymesitylen) und 25j (R1 = pyrol-1-yl) hergestellt. Es wurde beobachtet, dass die Größe des Substituenten das SCO-Verhalten (T1/2) beeinflusst. Ergänzend wurde der Einfluss des Gegenions anhand der Komplexe [Fe(25c)]2+∙2[BF4]– und [Fe(25c)]2+∙2[B(Ph)4]– untersucht. Das Gegenion B(Ph)4– ermöglicht intra- und intermolekulare π···π-Wechselwirkungen in der Zelle, welche die Übergangstemperature T1/2 (200 K) gegenüber dem BF4–-Komplex (175 K) erhöhen. Des Weiteren beeinflussen die Substituenten R1 an der Pyridin-Einheit die ubergangskomplexes T1/2 stärker als die Substituenten R2 an der Phenanthrolin-Einheit. So ist [Fe(25f)]2+∙2[BF4]– (R1 = Ph) ein reiner HS-Komplex, während der Komplex [Fe(25c)]2+∙2[BF4]– (R2 = Ph) ein SCO-System ist (T1/2 = 175 K). Die Erhöhung der Koordinationszahl von N6 auf N8 wurde über die Synthese von tetradentaten Liganden untersucht. Diese Erhöhung führt zu einem unerwarteten Koordinationsmodus. So bildet [Fe(25i)]2+∙2[BF4]– (R2 = pyrazol-1-yl) eine quadratisch-antiprismatische Koordinationssphäre (HS Eisen(II)-Komplex) und zeigt, wie erwartet, über den untersuchten Temperaturbereich keine Fe–N-Bindungsspaltung
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Heider, Silvio. "Synthese neuer tri- und hexadentater Stickstoffbasen für Eisen(II) Spin Crossover Komplexe." Doctoral thesis, Universitätsbibliothek Chemnitz, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-120783.
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Die vorliegende Arbeit thematisiert Eisen(II)-Komplexe mit Spinübergangseigenschaften. Dafür wurden neue hexadentate Liganden auf Basis von N,N'-Bis(2,2'-bipyridin-6-ylmethyl)-2,2'-biphenylendiamin entwickelt. Die in Kapitel 3.1 vorgestellten Systeme variieren dabei in den jeweiligen Substituenten der 6,6‘-Positionen der Biphenyleinheit. Es wird der Einfluss dieser Gruppen auf die magnetischen Eigenschaften der resultierenden Komplexe gezeigt. Im darauffolgenden Kapitel 3.2 wird ein variiertes Ligandensystem vorgestellt, in welchem anstelle einfacher Substituenten Donorfunktionen eingeführt wurden, sodass ein symmetrischer dinuklearer Eisen(II)-Komplex zugänglich war. In diesem sind die beiden Spin Crossover (SCO) Zentren erstmalig durch eine Biphenyleinheit verbrückt. Die durchgeführten Untersuchungen geben Hinweise auf eine allostere Wechselwirkung. Weiterhin wurde der Ligand durch N-Methylierung in ein tertiäres Amin überführt und die entsprechenden Komplexe mit Fe(II), Co(II) und Zn(II) synthetisiert (Kapitel 3.3). Diese wurden strukturell und elektrochemisch untersucht und hinsichtlich ihrer Redoxeigenschaften und Magnetismus mit den Komplexen der sekundären Amine verglichen. Ebenfalls wurde das Grundgerüst des auf sekundären Aminen basierenden Liganden so variiert, dass der terminale Donor durch stickstoffhaltige Fünfringheterocyclen – anstelle von Pyridin – verkörpert wurde (Kapitel 3.4). So konnten Eisen(II)-SCO Komplexe erhalten werden, welche eine wesentlich niedrigere Übergangstemperatur aufwiesen und somit magnetische Untersuchungen im Festkörper sowie des Photomagnetismus ermöglichten. Schließlich wurden neue tridentate Amine (2-(6-R-Pyridin-2-yl)-1,10-phenanthrolin) und deren Eisen(II)-Komplexe synthetisiert (Kapitel 3.5). Für einige dieser Komplexe konnte bereits das Spin Crossover Verhalten in Lösung untersucht werdenThe present thesis addresses iron(II) complexes with spin transition properties. For this purpose new hexadentate ligands were developed on the basis of N,N’-bis(2,2’-bipyridine-6-ylmethyl)-2,2’-biphenylenediamine. The systems introduced in chapter 3.1 vary in respect to the substituents in the 6,6’-positions of the biphenyl unit. The influence of these varying moieties on the magnetic behavior of the resulting complexes is shown. In the following chapter 3.2 a tuned ligand system is introduced, in which the substituents are donor functions so that a symmetrical dinuclear iron(II) complex was feasible. In this the two Spin Crossover (SCO) centers are for the first time connected by a biphenyl core. The executed experiments give hints to an allosteric interaction in this dinuclear compound. Moreover the ligand was reacted by N-methylation yielding a tertiary amine and the corresponding complexes with Fe(II), Co(II) and Zn(II) were synthesized (chapter 3.3). Those were investigated structurally and electrochemically and were then compared with the complexes with secondary amines in respect to their redox and magnetic properties. The ligand motif based on secondary amines was also modified in a way that the terminal donor was represented by nitrogen based five-ring heterocycles instead of pyridine (chapter 3.4). So iron(II) SCO complexes were available which showed much lower thermal transition temperatures and thus magnetic investigations in the solid state as well as investigations on the photomagnetic properties became possible. Ultimately, novel tridentate amines (2-(6-R-pyridine-2-yl)-1,10-phenanthroline) and the corresponding iron(II) complexes were synthesized (chapter 3.5). For some of those complexes the spin transition could already be monitored in solution
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Kipgen, Lalminthang [Verfasser]. "X-Ray Investigation of Ultra-Thin Spin-Crossover Molecular Films / Lalminthang Kipgen." Berlin : Freie Universität Berlin, 2019. http://d-nb.info/1187244244/34.
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Hiraoka, Nozomu, Hirofumi Ishii, Shunsuke Muto, John Hernlund, Kei Hirose, Shigehiko Tateno, Haruka Ozawa, and Ryuichi Nomura. "Spin crossover and iron-rich silicate melt in the Earth’s deep mantle." nature publishing group, 2011. http://hdl.handle.net/2237/20801.
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Marts, Amy Renae. "Magnetic Resonance Studies of Iron Spin Crossover Complexes and their Cobalt Analogs." Miami University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=miami1385033230.
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Hernandez, Gonzalez Edna Magdalena. "High spatial resolution investigation of spin crossover phenomena using scanning probe microscopies." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30081/document.
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Récemment, un grand nombre d'objets de taille nanométrique, incluant les nanoparticules, les films minces, les dispositifs nanostructurés, présentant des phénomènes de commutation impliquant différents états de spin, ont été développé pour des applications dans le domaine des capteurs et des systèmes nanophotoniques, nanoélectroniques et nanomécaniques. En effet, Ces nanomatériaux à conversion de spin présentent une dépendance en taille des propriétés physico-chimiques très intéressantes. Même si l'origine du phénomène de conversion de spin est purement moléculaire, le comportement macroscopique de ces systèmes à l'état solide est fortement influencé par les interactions intermoléculaires élastiques. On s'attend donc à ce que les propriétés coopératives et, de manière plus générale, le diagramme de phase, soient très dépendantes de la taille du système. Au-delà de la stabilité des phases, les cinétiques de transformation dépendent également de la taille du système. Dans ce contexte, des interactions élastiques fortes conduisent dans de nombreux cas à des transitions de type premier ordre accompagnées par une séparation de phase hétérogène. Les détails du mécanisme de la dynamique spatio-temporelle associée à la transition de spin restent encore inexplorés. L'ensemble de ces phénomènes observés dans les matériaux à transition de spin demande des méthodes de caractérisation possédant une capacité d'imagerie d'une grande résolution spatiale afin d'aller au-delà des techniques de microscopie optique en champ lointain habituellement employées. Par conséquence, l'objectif global de cette thèse de doctorat est de développer de nouvelles approches qui permettent de détecter le phénomène de transition de spin avec une résolution spatiale nanométrique. Pour observer la transition de spin thermique dans les films minces, nous avons utilisé pour la première fois la microscopie optique en champ proche (NSOM en Anglais) ainsi que la microscopie à force atomique (AFM en Anglais) en conjonction avec des dispositifs originaux de chauffage à l'échelle du nanomètre, conçus à partir de nanofils et fonctionnant par effet Joule. En utilisant ces techniques, le changement de l'état de spin a pu être observé avec une résolution sub-longueur d'onde au travers des changements des propriétés mécanique et optique des matériaux. Le NSOM en mode illumination, utilisé soit en luminescence ou en mode réflexion fournit un signal utile pour la détection du changement d'état de spin mais ne permet en revanche qu'une quantification limitée du phénomène en raison de l'instabilité des échantillons (photoblanchiment, ...) . D'un autre côté, les différents modes mécaniques AFM, incluant la spectroscopie à force rapide et l'analyse multifréquentielle, ont permis des mesures quantitatives et reproductibles avec une résolution nanométrique. En particulier, nous avons été capable de mesurer pour la première fois l'augmentation du module d'Young (env. 25-30%) observée lors de la transition de l'état Haut Spin vers l'état Bas Spin et nous avons utilisé cette propriété pour réaliser une imagerie quantitative de la transition de spin. Des mesures AFM ont été faites sur des monocristaux à transition de spin. Nous avons montré que les transferts thermiques entre la sonde et l'échantillon peuvent être utilisés pour manipuler la nucléation et la propagation des phases Haut et Bas Spin dans des cristaux. Par ailleurs, ces interactions sonde-échantillon rendent difficiles l'imagerie AFM de ces phénomènes. Néanmoins, les changements d'ordre topographique de la surface au cours de la transition de spin peuvent être observés et discutés en conjonction avec les résultats de spectroscopie Raman (cartographie) et microscopie optique en champ lointain. L'ensemble de ces résultats ouvre de nouvelles possibilités d'étude et de contrôle/manipulation de ces objets bistables à l'échelle du nanomètreRecently a variety of nanoscale objects, including nanoparticles, thin films and nanometric assemblies, exhibiting molecular spin-state switching phenomena have been developed for applications in sensors, nanophotonic, nanoelectronic and nanomechanical systems. These spin crossover nanomaterials have been also reported to exhibit interesting size-dependent properties. Indeed, even if the origin of the spin crossover phenomenon is purely molecular, the macroscopic behavior of these systems in the solid state is strongly influenced by elastic interactions between the molecules. These cooperative properties and, in general, the phase diagram are expected to depend strongly on the size of the material. Beyond the phase stability, the transformation kinetics is likely to display also size dependence. Indeed, the strong elastic interactions in these materials lead, in many cases, to first-order phase transitions and phase separation phenomena. Details of the associated spatio-temporal dynamics of spin crossover systems remain largely unexplored. All these size dependent and spatially heterogeneous phenomena in spin crossover materials call for appropriate characterization methods with high spatial resolution imaging capability, but to date only far-field optical microscopy has been used to this aim. Hence, the overall objective of this PHD thesis was to develop new approaches allowing to trigger and detect the spin crossover phenomenon with nanometric spatial resolution. For the detection of the thermally induced spin crossover in thin films, we used for the first time Near-Field Scanning Optical Microscopy (NSOM) and Atomic Force Microscopy (AFM) in conjunction with an original nano-heater device, based on Joule-heated metallic nanowires. Using these techniques the spin-state change in the films was inferred with sub-wavelength resolution through the associated optical and mechanical property changes of the material. Apertured NSOM used either in luminescence or reflectivity mode provided useful signal for detecting the spin-state switching phenomena, but rather limited quantification was possible due to sample stability issues (photobleaching, etc). On the other hand, AFM mechanical modes, including fast force spectroscopy and multifrequency analysis, allowed for quantitative and well-reproducible measurements with nanometric resolution. In particular, we have measured for the first time the increase of the Young's modulus (ca. 25-30 %) when going from the high spin to the low spin state and used this property for quantitative imaging of the spin transition. AFM measurements were also performed on spin crossover single crystals. We have shown that probe-sample thermal interactions can be used to manipulate the nucleation and propagation of the high spin and low spin phases in the crystals. On the other hand, these interactions make for difficulties for the AFM imaging of these phenomena. Nevertheless changes of the surface topography during the spin transition can be observed and discussed in conjunction with far-field optical microscopy and Raman spectroscopy data. The ensemble of these results open up new possibilities for the investigation and manipulation of these bistable objects at the nanoscale
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Diwa, Alex Timothy. "Spin Crossover in Iron(II) Coordination Frameworks: Structure and Host-Guest Chemistry." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/14163.
Full textAbstract:
Coordination framework synthesis offers a versatile path towards the construction of novel multifunctional materials. The incorporation of metal centres capable of spin-state switching into robust framework hosts allows for the integration of the two properties of spin crossover and nanoporosity. By combining these two functionalities, the genesis of materials that are able to respond in some physical manner (electronic, structural and optical) to their environment can be envisaged, with applications directed towards displays, information storage and sensing devices. To this aim, a range of iron(II) coordination framework materials have been synthesised based on three general structure types: bimetallic Hofmann-type and Hofmann-related systems of the form [FeII(L)M(CN)4]·xGuest (1-5, 12-14; L = bis-unidentate ligand; M = Ni, Pd, Pt) or [FeII(L)(M(CN)4)2]·xGuest (6-8; M = Ag, Au), SCOF-type systems of the form [FeII(L)2(XCN)2]·xGuest (9-11; X = S, Se) and porphyrinic frameworks (15-20). All were structurally characterised by single-crystal X-ray diffraction and variable-temperature magnetic susceptibility measurements. A series of bis-unidentate ligands based on an amide/urea functional group motif were incorporated into the materials 1-11. Systematic alteration of the ligand length in the family of Hofmann-type phases 1-5 revealed strong structure-property correlations. The interpenetrated phases 6-8 were each found to undergo thermally-induced spin transitions, with the SCOF-type phases 9-11 remaining in high-spin to 100 K. Guest-dependent spin crossover behaviour was explored in the Hofmann-type phases 12-14 (M = Ni, Pd, Pt), with one material exhibiting unusual temperature-dependent behaviour with two separate regions of bistability. Finally, a series of frameworks incorporating a tetratopic porphyrinic ligand in combination with FeII and the counterions XCN- (X = S, Se, BH3), N(CN)2 and Au(CN)2- were structurally characterised, and comprise the materials 15-20. “The files in Appendix A are in .cif format (Crystallographic Information File) and can be opened with the software Mercury (see website). Mercury can be run on Windows, Linux or Mac OS X.”
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Ando, Hideo. "Molecular Insights into Spin Crossover Phenomena of 1st-Row Transition Metal Complexes." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/174958.
Full textAbstract:
著作権表示ページを末尾に追加 (2019.12.11)Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第17592号
工博第3751号
新制||工||1572(附属図書館)
30358
京都大学大学院工学研究科分子工学専攻
(主査)教授 佐藤 啓文, 教授 田中 一義, 教授 北川 進
学位規則第4条第1項該当
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Pasquier, Rémi. "Theory of the electronic structure of spin crossover molecules on metallic surfaces." Electronic Thesis or Diss., Strasbourg, 2024. http://www.theses.fr/2024STRAE003.
Full textAbstract:
L'objectif de cette thèse est l’étude du comportement des molécules à transition de spin adsorbées sur des surfaces métalliques, en utilisant des méthodes ab-initio basées sur la théorie de la fonctionnelle de densité (DFT). En premier lieu, nous redécrivons les états de spin d'une molécule de FePhen et son interaction avec un substrat métallique de Cu(00l) et nous la comparons a une molécule de FePhen dopée par fluorination. Nous montrons ainsi une inversion des états de spin après fluorination, que nous étudions en détail en utilisant l 'analyse de Bader afin de déterminer les transferts de charge intramoléculaires, ainsi que la méthode « Nudged Elastic Band » (NEB) pour l’étude du chemin de transition entre les états de spin. Finalement, nous calculons le spectre des phonons dans ces systèmes dans l'approximation harmonique, et nous montrons les différences importantes entre les modes de la molécule non dopée et dopée, ainsi que leur influence sur l’évolution avec la température de grandeurs thermodynamiques telles que l’énergie libre, et nous les utilisons avec la formule de Slichter-Drickamer afin de calculer l’évolution de la fraction en état HS avec la température. Nous introduirons également nos premiers résultats d'un calcul post-harmonique du spectre de phonons en dynamique moléculaire en utilisant la fonction d'autocorrélation des vitesses , afin d’étudier l’évolution des principaux modes du spectre eux-mêmes avec la température. En un second temps, nous développons et implémentons dans VASP le calcul des spectres d'absorption a rayons X (XAS et XMCD) afin d'obtenir de manière théorique les spectres au seuil L23 dans l'atome de fer de la molécule de FePhen, avec et sans la surface. En premier lieu, nous démontrons que la contribution des ondes planes ace spectre est négligeable, ce qui facilite et accélère grandement le calcul, mais également que l'ajout d'un trou de cœur statique n’améliore pas dans ce cas les résultats obtenus. Ensuite, nous montrons l'impact relativement faible de ce substrat sur ces spectres. En outre, nous montrons que la déformation des complexes vis-a-vis d'une géométrie octaèdrale parfaite induit des effets perceptible sur le spectre ainsi que sur l'anisotropie magnétique de la molécule. Finalement, nous implémentons dans VASP le calcul du tenseur dipolaire magnétique et nous mettons en évidence sa contribution importante, mais très souvent négligée, dans l'évaluation des règles d’intégration de ces spectres. Finalement, nous implémentons le calcul des images de microscopie a effet tunnel (STM) au-delà de l'approximation de Tersoff-Hamann (TH), en utilisant la règle différentielle de Chen, dans les cas idéaux et avec des pointes réalistes, et avec la formule de Bardeen complète. Nous comparons ces résultats avec les images déjà obtenues auparavant avec cette première approximation TH mais également aux quelques images expérimentales. Nous montrons ainsi qu’au-delà la claire et apparente similarité entre toutes les méthodes, les différentes approches présentent des détails fins clairement distinguables qui pourraient être observés expérimentalement avec des images de meilleure précision que les quelques résultats déjà disponiblesThe aim of this thesis is to study the behaviour of spin-transition molecules adsorbed on metal surfaces, using ab-initio methods based on density functional theory (DFT). First, we re-describe the spin states of a FePhen molecule and its interaction with a Cu(00l) metal substrate and compare it to a fluorine-doped FePhen molecule. We show an inversion of the spin states after fluorination, which we study in detail using Bader analysis to determine the intramolecular charge transfers, and the Nudged Elastic Band (NEB) method to study the transition path between the spin states. Finally, we calculate the phonon spectrum in these systems in the harmonic approximation, and we show the important differences between the modes of the undoped and doped molecule, as well as their influence on the evolution with temperature of thermodynamic quantities such as the free energy, and we use them with the Slichter Drickamer formula to calculate the evolution of the fraction in the HS state with temperature. We will also introduce our first results for a post-harmonic calculation of the phonon spectrum in molecular dynamics using the velocity autocreelation function, in order to study the evolution of the main modes of the spectrum themselves with temperature. Secondly, we develop and implement in VASP the calculation of X-ray absorption spectra (XAS and XMCD) in order to obtain theoretically the L23 threshold spectra in the iron atom of the FePhen molecule, with and without the surface. Firstly, we show that the contribution of plane waves to this spectrum is negligible, which greatly facilitates and accelerates the calculation, but also that the addition of a static core hole does not improve the results obtained in this case. We then show the relatively small impact of this substrate on these spectra. In addition, we show that the deformation of the complexes with respect to a perfect octahedral geometry induces perceptible effects on the spectrum as well as on the magnetic anisotropy of the molecule. Finally, we implement the calculation of the magnetic dipole tensor in VASP and highlight its important, but very often neglected, contribution to the evaluation of the integration rules for these spectra. Finally, we implement the computation of scanning tunneling microscopy (STM) images beyond the Tersoff-Hamann (TH) approximation, using Chen's differential rule, in the ideal cases and with realistic tips, and with the full Bardeen formula. We compare these results with images obtained previously with this first TH approximation, as well as with the few experimentally available images. We thus show that beyond the clear and apparent similarity between all the methods, the different approaches present clearly distinguishable fine details that could be observed experimentally with images of better precision than the few results already available
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Mullaney, Benjamin Ross. "Guest-Dependence on Spin Crossover and Thermal Expansion in Nanoporous Coordination Framework Materials." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/9806.
Full textAbstract:
Coordination framework materials have attracted much interest in modern chemistry due to the plethora of properties that they may possess. The frameworks described in this thesis demonstrate the properties of spin crossover, anomalous thermal expansion, and nanoporosity, which enables guest-dependent studies into the material behaviour. The first frameworks described are the [Fe(bpac)M(CN)4]•x(bpac){guest} (M = Ni, Pd, Pt; bpac = 1,4-bis(4′-pyridyl)acetylene) family. The properties of the alcohol-solvated [Fe(bpac)Pd(CN)4]•x(bpac) (x = 0.4, 0.5) frameworks were studied, and the major guest influence on the resulting spin crossover behaviour was determined to be due to an internal pressure effect produced by the kinetic volume and compressibility of the guest. By obtaining a variety of EtOH adsorption isotherms and isobars, a Temperature-Pressure phase diagram of SCO was produced for the [Fe(bpac)Pd(CN)4]•0.4(bpac){EtOH} material. In addition to these frameworks, the behaviour of the [Fe(bpac)(Au(CN)2)2)]•{guest} framework material was also investigated. This framework demonstrated unprecedented multifunctional behaviour, with a synergistic interplay between the spin crossover, lattice structure and host–guest properties. The framework lattice was exceptionally flexible, and displayed a facile ‘scissor-type’ motion of the {Fe(Au(CN)2)2} (4,4) grids. Due to the extreme conformational flexibility of the {Fe(Au(CN)2)2} (4,4)-grids of this material, the [Fe(bpac)(Au(CN)2)2)]•{EtOH} sample displayed colossal uniaxial thermal expansion behaviour. Below the spin transition, the a parameter displayed a maximum thermal expansion coefficient of −1070 × 10−6 K−1, which is an order of magnitude greater than any yet reported for this quantity. Guest-dependent studies on this framework demonstrate the strong effect of guest properties on the conformation of the framework lattice and the spin transition behaviour.
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Alfurayj, Ibrahim A. "Solid-state Spin Equilibrium in Tetrakis(N,N'-diethylthiourea)nickel(II) dichloride, [Ni(detu)4]Cl2: Structural and Thermal Characterization." Ohio University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1435790988.
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