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1
Schory, David Henry. "Quantum Chemical Investigations of Nucleophilic Aromatic Substitution Reactions and Acid Dissociations of Aliphatic Carboxylic Acids." Wright State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=wright1253480264.
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Esplugas, Ricardo Oliveira. "Density functional theory and time-dependent density functional theory studies of copper and silver cation complexes." Thesis, University of Sussex, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496931.
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A particular emphasis of this thesis has been to provide insight into the underlying stability of these complexes and hence interpret experimental data, and to establish the development of solvation shell structure and its effect on reactivity and excited states. Energy decomposition analysis, fragment analysis and charge analysis has been used throughout to provide deeper insight into the nature of the bonding in these complexes. This has also been used successfully to explain observed preferential stability and dissociative loss products.
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Ke, Hongwei. "Density functional theory studies on glycine conformers and glycine-water complexes /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202009%20KE.
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Paget, Veronica J. "The modelling of transition metal centres using molecular mechanics and density functional theory." Thesis, University of Bath, 1996. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320428.
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Dang, Li. "Density functional theory studies of copper(I) mediated borylation and carboxylation reactions /." View abstract or full-text, 2010. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202010%20DANG.
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Galstyan, Artur [Verfasser]. "Accurate redox potentials of transition metal complexes calculated using density functional theory and electrostatics / Artur Galstyan." Berlin : Freie Universität Berlin, 2008. http://d-nb.info/1023261499/34.
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Brett, Constance M. "Investigation of the structure and bonding of metal complexes through the use of density functional theory." Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1118688725.
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Thesis (Ph. D.)--Ohio State University, 2005.<br>Title from first page of PDF file. Document formatted into pages; contains xxxi, 309 p.; also includes graphics Includes bibliographical references. Available online via OhioLINK's ETD Center
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Durivage, Jason Curtis. "Ligand Effects on Metal-Metal Bonding: Photoelectron Spectroscopy and Electronic Structure Calculations of Dimetal Paddlewheel Complexes." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/145427.
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Paddlewheel complexes are molecules in which two interacting metal atoms are bridged by four chelating ligands. This class of complexes has a large range of electronic variability while keeping a rigid geometric structure. This variability has led to their use as catalysts, strong reductants, anti-tumor agents, and electron transfer agents. This dissertation examines the effects of changing both the dimetal core and the surrounding ligands on the electronic structure properties of the paddlewheel complexes. Examination of Bi₂(O₂CCF₃)₄, a p-orbital dimetal paddlewheel complex, provided a way to probe the orbitals that are important in metal-ligand σ bonding. The b(1g) and b(2u) ligand orbitals of Bi₂(O₂CCF₃)₄ have no dimetal orbital counterpart, unlike the case of the more familiar d-orbital dimetal paddlewheel complexes such as Mo₂(O₂CCF₃)₄. This had the effect of destabilizing these ligand orbitals compared to d-orbital paddlewheel complexes. The ligand a1g orbital in Bi₂(O₂CCF₃)₄ was also destabilized due to nodal differences in the dimetal σ orbital. The unusual coincidence of Mo-Mo σ and π ionization bands is due to a greater amount of ligand character in the Mo-Mo σ orbital compared to its ditungsten analogue, which has separate ionization bands for the σ and π bonds. A series of p-substituted dimolybdenum tetrabenzoate complexes was synthesized and studied by photoelectron spectroscopy in order to further examine the delocalization of electron density from the metals to the ligands in these complexes. A 0.89 eV shift in the δ ionization band was observed from Mo₂(O₂CPh-p-OMe) ₄ and Mo₂(O₂CPh-p-CF₃)₄. Overlap effects are the major factor causing the shift in the δ bond ionization, as the calculated charges on the molybdenum and oxygen atoms did not vary significantly on change of substituent. Molybdenum and tungsten guanidinate paddlewheel complexes have promise as good reducing agents due to their extremely low ionization energies. The solubility of the complexes poses a problem for their widespread adoption for use as reducing agents. Alkyl substituents were added to the complexes to increase their solubility. W₂(TEhpp)₄ was observed to have the lowest ionization energy at 3.71 eV (vertical ionization) and 3.40 eV (onset ionization) of any molecule yet prepared.
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Collins, Clare R. "The chemistry and structure of surface complexes of Cd'2'+,Hg'2'+,Sr'2'+, and Zn'2'+ on goethite : insights from density functional theory and EXAFS spectroscopy." Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388020.
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Dain, Ryan P. "Investigation of gas-phase metal ion complexes using infrared multiple photon dissociation spectroscopy and density functional theory calculations." Thesis, Wichita State University, 2010. http://hdl.handle.net/10057/3300.
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A combination of theoretical chemistry and “action” spectroscopy has become the most
used tool for the exploration of gas-phase molecular ions. In this study, density functional theory
(DFT) calculations were used to test the validity of conclusions drawn from the results of a
matrix-isolation infrared (MI-IR) experiment and develop a modeling method that could be used
for metal-coordinating chlorate ion pairs. That modeling method was then used in comparison
with experimental infrared multiple photon dissociation (IRMPD) spectroscopy to determine the
structures of metal-chlorate anions. In addition to structural information, the effect of the
modeling method on spectral correlation was also investigated.<br>Thesis (M.S.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Chemistry
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Martin, Claudia. "Density functional study of the electronic and magnetic properties of selected transition metal complexes." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2014. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-134958.
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Die vorliegende Promotionsarbeit “Density functional study of the electronic and magnetic properties of selected transition metal complexes” beschäftigt sich mit dem Zusammenhang zwischen strukturellen Merkmalen sowie elektronischen und magnetischen Eigenschaften von Einzelmolekül-Magneten. Im Wesentlichen konnte dabei gezeigt werden, dass die magnetischen Eigenschaften sowohl von strukturellen Merkmalen als auch von den elektronischen Eigenschaften bestimmt werden. Des Weiteren ergab sich, dass verschiedene Kenngrößen der magnetischen Eigenschaften (im speziellen der magnetische Grundzustand S sowie die magnetische Anisotropie D) miteinander korreliert sind. Dies ist im Besonderen für eine mögliche Anwendung von Einzelmolekül-Magneten im Bereich der Datenspeicherung von Bedeutung.
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Debrah, Duke A. "Molecular Modeling of Dirhodium Complexes." Digital Commons @ East Tennessee State University, 2014. https://dc.etsu.edu/etd/2426.
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Dirhodium complexes such as carboxylates and carboxylamidates are very efficient metal catalysts used in the synthesis of pharmaceuticals and agrochemicals. Recent experimental work has indicated that there are significant differences in the isomeric ratios obtained among the possible products when synthesizing these complexes. The relative stabilities of the Rh2(NPhCOCH3)4 tolunitrile complexes, Rh2(NPhCOCH3)4(NCC6H4CH3)2, were determined at the HF/LANL2DZ ECP, 6-31G and DFT/B3LYP/LANL2DZ ECP, 6-31G levels of theory using NWChem 6.3. The LANL2DZ ECP (effective core potential) basis set was used for the rhodium atoms and 6-31G basis set was used for all other atoms. Specifically, the o-tolunitrile, m-tolunitrile, and p-tolunitrile complexes of the 2,2-trans and the 4,0- isomers of Rh2(NPhCOCH3)4 were compared.
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Parveen, Riffat. "Computational Studies of C-H Bond Activation and Ethylene Polymerization Using Transition Metal Complexes." Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1505131/.
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This work discusses the C-H bond activation by transition metal complexes using various computational methods. First, we performed a DFT study of oxidative addition of methane to Ta(OC2H4)3A (where A may act as an ancillary ligand) to understand how A may affect the propensity of the complex to undergo oxidative addition. Among the A groups studied, they can be a Lewis acid (B or Al), a saturated, electron-precise moiety (CH or SiH), a σ-donor (N), or a σ-donor/π-acid (P). By varying A, we seek to understand how changing the electronic properties of A can affect the kinetics and thermodynamics of methane C–H activation by these complexes. For all A, the TS with H trans to A is favored kinetically over TS with CH3 trans to A. Upon moving from electron-deficient to electron-rich moieties (P and N), the computed C–H activation barrier for the kinetic product decreases significantly. Thus, changing A greatly influences the barrier for methane C–H oxidative addition by these complexes. Secondly, a computational study of oxidative addition (OA) of methane to M(OC2H4)3A (M = Ta, Re and A = ancillary ligand) was carried out using various computational methods. The purpose of this study was to understand how variation in A and M affects the kinetics and thermodynamics of OA. Results obtained from MP2 calculations revealed that for OA of CH4 to Re(OC2H4)3A, the order of ΔG‡ for a choice of ancillary ligand is B > Al > SiH > CH > N > P. Single point calculations for ΔG‡ obtained with CCSD(T) showed excellent agreement with those computed with MP2 methods. MCSCF calculations indicated that oxidative addition transition states are well described by a single electronic configuration, giving further confidence in the MP2 approach used for geometry optimization and ΔG‡ determination, and that the transition states are more electronically similar to the reactant than the product. Thirdly, a computational study of olefin polymerization has been performed on 51 zirconocene catalysts. The catalysts can be categorized into three classes according to the supporting ligand framework: Class I - Cp2ZrCl2 (ten catalysts), Class II - CpIndZrCl2 (thirty-eight catalysts), and Class III - Ind2ZrCl2 (three catalysts), Cp = η5-cyclopentaidenyl, Ind = η5-indenyl. Detailed reaction pathways, including chain propagation and chain termination steps, are modeled for ethylene polymerization using Class II catalysts. Optimized structures for reaction coordinates indicated the presence of α-agostic interactions in the transition states (TSs) for both the 1st and 2nd ethylene insertions as well as in the ethylene π-complex of the Zr-nPr cation. However, β-agostic interactions predominate in the cationic n-propyl and n-pentyl intermediates. The calculated relative Gibbs free energies show that the TS for insertion of ethylene into the Zr-CH3+ bond is the highest point on the computed reaction coordinates. This study, in concert with previous work, suggests that the type of ring attached to Zr (Cp vs. Ind) affects the reaction kinetics and thermodynamics less significantly than the type of substituents attached to the Cp and indenyl rings, and that substituent effects are even greater than those arising from changing the metal (Zr vs. Hf)
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Kirgan, Robert A. "Diimine complexes of ruthenium(ii), rhenium(i) and iron(ii): from synthesis to DFT studies." Diss., Wichita State University, 2007. http://hdl.handle.net/10057/3981.
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The chloro and pyridinate derivatives of rhenium(I) tricarbonyl complexes containing the diimine ligands 2,2’-bipyrazine (bpz) and 5,5’-dimethyl-2,2’-bipyrazine (Me2bpz) are discussed. When compared to similar rhenium(I) tricarbonyl complexes of 2,2’-bipyridine (bpy) and 2,2’-bipyrimidine (bpm), the Me2bpz complexes are comparable to bpm derivatives and their properties are intermediate between those of bpy and bpz complexes.
Also discussed is the synthesis and properties of two new analogues of ruthenium(II) tris-bipyridine, a monomer and dimer. The complexes contain the ligand 6,6’-(1,2-ethanediyl)bis-2,2’-bipyridine (O-bpy) which contains two bipyridine units bridged in the 6,6’ positions by an ethylene group. Crystal structures of the two complexes formulated as [Ru(bpy)(O-bpy)](PF6)2 and [(Ru(bpy)2)2(O-bpy)](PF6)4 reveal structures of lower symmetry than D3 which affects the electronic properties of the complexes as revealed by Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TDDFT) calculations. Iron(II) tris-bipyrazine undergoes dissociation in solution with loss of the three bipyrazine ligands. The rate of the reaction in acetonitrile depends on the concentration of anions present in the solution. The rate is fastest in the presence of Cl- and slowest in the presence of Br-. In a second discussion DFT calculations are used to explore four iron(II) diimine complexes. DFT calculations show the higher energy HOMO (highest occupied molecular orbital) orbitals of the four complexes are metal centered and the lower energy LUMO (lowest unoccupied molecular orbitals) are ligand centered.<br>Dissertation(Ph.D.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Chemistry
15
Pearson, Stephen. "High oxidation state carbene complexes for C-H bond activation catalysis." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/7570.
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Chapter one is an introduction to the less common coordination and oxidation chemistry of palladium; complexes containing Pd-OR, Pd-NR2 and those in the oxidation states of +IV. An outline of PdII/IV catalysed ligand-directed oxidative functionalisation is also included. Chapter two covers the design and synthesis of a range of tethered N-heterocyclic carbene (NHC) complexes of Pd. In addition, the syntheses of a number of new tethered NHC ligands are described. The use of Density Functional Theory (DFT) to model the complexes in this thesis was explored. Chapter three describes the synthesis and characterisation of PdIV halide complexes. The relevance of these compounds to PdII/IV catalysed ligand-directed oxidative functionalisation is explored. DFT was used to probe the reaction pathway for N-bromosuccinimide and iodobenzene dichloride. Chapter four examines reactions with oxidants used to form C-O and C-C bonds. The reaction pathway for iodobenzene diacetate was investigated using DFT. Chapter five contains experimental details and characterising data for the compounds reported.
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Najafian, Ahmad. "Activation of Small Molecules by Transition Metal Complexes via Computational Methods." Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1703353/.
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The first study project is based on modeling Earth abundant 3d transition-metal methoxide complexes with potentially redox-noninnocent ligands for methane C–H bond activation to form methanol (LnM-OMe + CH4 → LnM–Me + CH3OH). Three types of complex consisting of tridentate pincer terpyridine-like ligands, and different first-row transition metals (M = Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) were modeled to elucidate the reaction mechanism as well as the effect of the metal identity on the thermodynamics and kinetics of a methane activation reaction. The calculations showed that the d electron count of the metal is a more significant factor than the metal's formal charge in controlling the thermodynamics and kinetics of C–H activation. These researches suggest that late 3d-metal methoxide complexes that favor σ-bond metathesis pathways for methane activation will yield lower barriers for C–H activation, and are more profitable catalyst for future studies.
Second, subsequently, on the basis of the first project, density functional theory is used to analyze methane C−H activation by neutral and cationic nickel-methoxide complexes. This study identifies strategies to further lower the barriers for methane C−H activation through evaluation of supporting ligand modifications, solvent polarity, overall charge of complex, metal identity and counterion effects. Overall, neutral low coordinate complexes (e.g. bipyridine) are calculated to have lower activation barriers than the cationic complexes. For both neutral and cationic complexes, the methane C−H activation proceed via a σ-bond metathesis rather than an oxidative addition/reductive elimination pathway. Neutralizing the cationic catalyst models by a counterion, BF4-, has a considerable impact on reducing the methane activation barrier free energy.
Third, theoretical studies were performed to explore the effects of appended s-block metal ion crown ethers upon the redox properties of nitridomanganese(V) salen complexes, [(salen)MnV(N)(Mn+-crown ether)]n+, where, M = Na+, K+, Ba2+, Sr2+ for 1Na, 1K, 1Ba, 1Sr complexes respectively; A = complex without Mn+-crown ether and B = without Mn+). The results of the calculations reveal that ΔGrxn(e ̶ ) and thus reduction potentials are quite sensitive to the point charge (q) of the s-block metal ions. Methane activation by A, 1K and 1Ba complexes proceeds via a hydrogen atom abstraction (HAA) pathway with reasonable barriers for all complexes with ~ 4 kcal/mol difference in energy, more favorable free energy barrier for the complexes with higher point charge of metal ion. Changes in predicted properties as a function of continuum solvent dielectric constant suggest that the primary effect of the appended s-block ion is via "through space" interactions.
Finally, a comprehensive DFT study of the electrocatalytic oxidation of ammonia to dinitrogen by a ruthenium polypyridyl complex, [(tpy)(bpy)RuII(NH3)]2+ (complex a), and its NMe2-substituted derivative (b), is presented. The thermodynamics and kinetics of electron (ET) and proton transfer (PT) steps and transition states are calculated. NMe2 substitution on bpy reduces the ET steps on average 8 kcal/mol for complex b as compared to a. The calculations indicate that N–N formation occurs by ammonia nucleophilic attack/H-transfer via a nitrene intermediate, rather than a nitride intermediate. Comparison of the free energy profiles of Ru-b with its first-row Fe congener reveals that the thermodynamics are less favorable for the Fe-b model, especially for ET steps. The N-H bond dissociation free energies (BDFEs) for NH3 to form N2 show the following trend: Ru-b <Ru-a <Fe-b, indicating the lowest and most favorable BDFEs for Ru-b complex.
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Saukkoriipi, J. (Jaakko). "Theoretical study of the hydrolysis of aluminum complexes." Doctoral thesis, University of Oulu, 2010. http://urn.fi/urn:isbn:9789514261831.
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This thesis focuses on the molecular-level chemistry of the solvation of aluminum salts. Fundamental aspects such as, structural characteristics of the aluminum molecules, hydrolysis, acidity, solvation structure, effect of counter ions, and chemical stability are discussed herein. Static computations augmented with the conductor-like screening model (COSMO) were used to investigate hundreds of planar and cyclic configurations of dimeric, trimeric, tetrameric, and pentameric aluminum complexes. Car–Parrinello molecular dynamics (CPMD) calculations were used to expand investigations to aqueous environments.
This thesis consists of four articles and one additional article. The first paper focuses on the structural analysis of the hydrolysis products of AlCl3 · 6H2O. Dimeric, trimeric, and tetrameric aluminum (chloro)hydroxides were investigated in both gas and liquid phase. The liquid environment was modeled by using COSMO.
The second and the additional paper concentrate on the chemistry of aluminum sulfate complexes. The second article focuses on identifying hydrolysis products of AlCl3 · 6H2O in the presence of sulfate (H2SO4). The additional paper focuses on the structural characteristics of the hydrolysis products of Al2 (SO4)3 · 18H2O. Structural information was deduced from the ESI MS results with the aid of computational methods. Detected cationic structures closely resembled the aluminum chlorohydrate analogues introduced in the first paper.
The third and fourth articles are devoted to the hydrolysis, stability, and dynamics of dimeric and pentameric aluminum (chloro)hydroxides in aquatic environments. During the CPMD simulations, several spontaneous associative hydration reactions were detected in the primary hydration shell of the complexes. Dimeric aluminum chlorohydrates were detected to be stable in liquid conditions, whereas the pentameric aluminum complexes experienced significant topological changes during the simulations. Constrained simulations were used to reveal the role of chloride ions in the hydrolysis processes of dimeric complexes. The effect of the empirical van der Waals corrections to the dynamics of the simulations was also tested for the pentameric system.
The results of this thesis showed unequivocally that computational chemistry provides effective tools for structural analysis of inorganic complexes such as, aluminum chlorohydrates and sulfates in both gas and liquid phase. In addition, calculations provided answers to the anomalies detected in the experiments. Hence, theoretical methods are highly recommended to be used alongside with conventional experimental methods in the interpretation of the aluminum species in aqueous solutions and to widen the overall chemical perspective of the hydrolysis of aluminum salts.
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Bezuidenhout, Charl Xavier. "Polar ordering of guest molecules in host-guest inclusion complexes." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/18107.
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Thesis (MSc)--Stellenbosch University, 2011.<br>ENGLISH ABSTRACT: 2,7-dimethylocta-3,5-diyne-2,7-diol forms inclusion complexes with various guests molecules, where the guest molecules are polar-ordered. A Cambridge Structural Database (CSD) search revealed ten inclusion complexes where the guest molecules were polar-ordered. Using Density Functional Theory (DFT) computational methods (in the absence of the host), we evaluated the intra-channel and lateral guest-guest interactions between the guest molecules.
Two polar-ordered inclusion complexes ((1,4,7-cyclohexane-1,2,4,5,7,8-hexaoxonane)·CHCl3 and (2,4,6-(endolongifolyl)-1,3,5-trioxane)·CDCl3) were singled out in the CSD search for further studies along with 2,7-dimethylocta-3,5-diyne-2,7-diol. Synthesis of any 1,2,4,5,7,8-hexaoxonane and 1,3,5-trioxane derivatives was attempted to establish whether the polar-ordering ability extends into the family of compounds. We managed to produce three new polar-ordered inclusion complexes with 2,7-dimethylocta-3,5-diyne-2,7-diol (ClC(CH3)3, BrC(CH3)3 and IC(CH3)3), thus extending the series to six guest polar-ordered systems. We were only able to synthesise 1,4,7-cyclohexane-1,2,4,5,7,8-hexaoxonane and produce the CHCl3 inclusion complex and one new polar-ordered inclusion complex (CHBr3). Three 1,3,5-trioxanes was synthesised (the cyclohexyl, cyclohex-3-en-1-yl and cyclopentyl derivatives), which did not include any solvents. However, these 1,3,5-trioxanes also form polar-ordered crystals.
These compounds and inclusion complexes were analysed by means of single crystal X-ray diffraction to determine their crystal structures. All the crystal structures could be solved and refined to adequate accuracy (except for 2,4,6-tri(cyclopentyl)-1,3,5-trioxane) with no disorder of the guest molecules (where applicable) and their polar-ordering property investigated. Due to their vast molecular differences, these compounds were studied separately by means of visual crystal structure analysis and computational modelling techniques (Density functional theory, molecular mechanics, molecular dynamics and molecular quench dynamics).<br>AFRIKAANSE OPSOMMING: 2,7-dimetielokta-3,5-diyn-2,7-diol vorm insluitingskomplekse met verskeie molekules as gaste, waar die gas-molekules polêr georden is. 'n Cambridge Struktuur Databasis (CSD) soektog lewer tien insluitings komplekse waarvan die gas-molekules polêr georden is. Deur gebruik te maak van Digtheidsfunksionele teorie (DFT) berekeninge (in die afwesigheid van die gasheer) het ons die inter-kanaal en wedersydse gas-gas interaksies tussen die gas molekules geëvalueer.
Twee polêr geordende insluitingskomplekse ((1,4,7-sikloheksaan-1,2,4,5,7,8-heksaoksonaan)·CHCl3 en (2,4,6-(endolongifolyl)-1,3,5-trioksaan)·CDCl3) is uitgesonder uit die CSD soektog vir verdere studies saam met 2,7-dimetielokta-3,5-diyn-2,7-diol. Aanslag was gemaak om enige 1,2,4,5,7,8-heksaoksonaan en 1,3,5-trioksaan derivate te sintetiseer en vas te stel of die polêre ordensvermoë oor die familie van verbindings strek. Ons het daarin geslaag om drie nuwe polêr geordende insluitingskomplekse op te lewer met 2,7-dimetielokta-3,5-diyn-2,7-diol (Cl(CH3)3, BrC(CH3)3 en I(CH3)3), en sodoende die reeks uitgebrei na ses gaste wat polêr geordende insluitingskomplekse vorm. Net 1,4,7-sikloheksaan-1,2,4,5,7,8-heksaoksonaan kon gesintetiseer word en dit lewer twee polêr geordende insluitingskomplekse (CHCl3 en CHBr3 (nuut)). Drie 1,3,5-trioksane is gesintetiseer (die sikloheksiel, sikloheks-3-een-1-iel en siklopentiel derivate) en het nie enige oplosmiddels (gaste) ingesluit nie. Nietemin vorm hiedie 1,3,5-trioksane ook polêr geordende kristalle.
Hierdie verbindings en insluitingskomplekse is geanaliseer deur middel van enkelkristal X-straal diffraksie om hul kristalstrukture te bepaal. Alle kristalstrukture was opgelos en verwerk tot voldoende akkuraatheid (behalwe vir 2,4,6-tri(siklopentiel)-1,3,5-trioxane) met geen wanorde in die gas molekuul posisies nie (waar van toepassing) en hul polêre ordensvermoë is ondersoek. As gevolg van groot verskille in hul molekulêre strukture, is hierdie verbindings afsonderlik bestudeer deur middel van molekulêre modellerings metodes (Digtheidsfunksionele teorie, molekulêre meganika, molekulêre dinamika en molekulêre stakings dinamika).
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Li, Yunliang, and 李運良. "Time-resolved resonance Raman and density functional theory investigations of selected isopolyhalomethanes, haloalkyl radicals andpolyhalomethane/halogen atom molecular complexes and their reactions." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B31245717.
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Govender, Krishna Kuben. "Theoretical studies of nitrilotriacetic acid and nitrilotripropionic acid geometries for estimation of the stability of metal complexes by Density Functional Theory." Diss., University of Pretoria, 2009. http://hdl.handle.net/2263/27811.
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Nitrilotriacetic Acid (NTA) is an organic ligand which has been extensively studied due to its biological significance and excellent chelating properties. Nitrilotripropionic Acid (NTPA) is a ligand that is believed to possess similar properties to NTA, but has not been as extensively studied. It has been experimentally determined that metal complexes of NTA are orders of magnitude stronger than those formed with NTPA. This is surprising, especially considering that the ligands do not differ that much from each other. NTPA contains an additional –CH2– group in each of the acid containing arms as compared to NTA. The aim of these studies were to explain, theoretically, why this is the case. Analyses were conducted with a number of software programs including, Gaussian 03, Schrödinger Maestro and AIM 2000. All Density Functional Theory (DFT) studies were conducted in solvent at the RB3LYP/6-311+G(d,p) level of theory in conjunction with a number of different solvation models. En route to explaining why the complexes differ in stability a new methodology was utilized (isodesmic reactions) in which the four stepwise protonation constants of both NTA and NTPA were successfully predicted; in fact these were the most accurate values predicted to date by DFT methods. The final step of these studies focused on predicting stability constants of metal (Zn2+ and Ni2+) complexes of NTA and NTPA. These predictions were not as accurate as those achieved for the prediction of protonation constants; however, success was achieved in predicting the trend – complexes with NTA are orders of magnitude stronger than complexes formed with NTPA. The most important observation revealed that H–clashes and C–H∙∙∙O hydrogen bonds present in M(NTPA) complexes, which are not present in M(NTA) complexes, result in the formation of additional rings which contributes to the formation of a cage. It was discovered that the H-clashes present in the M(NTPA) complexes were contributing to the overall stability of the molecule. This is completely contradictory to a previous explanation in which H-clashes, being a result of steric crowding, resulted in destabilization of a complex. If the H-clashes were not present in the M(NTPA) complexes there would not be enough stabilizing factors present in the molecule which will inevitably result in the non-existence of M(NTPA) complexes. Copyright<br>Dissertation (MSc)--University of Pretoria, 2010.<br>Chemistry<br>unrestricted
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Magero, Denis. "Electrochemical and photochemical studies of some remarkable ruthenium complexes." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAV071/document.
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Cette thèse fait partie d’un projet franco-keyan dénommé ELEPHOX (ELEctrochemical and PHOto Properties of Some Remarkable Ruthenium and Iron CompleXes). En particulier, notre focus est la continuation du travail de C. Muhavini Wawire, Damien Jouvenot, Fréd erique Loiseau, Pablo Baudin, Sébastien Liatard, Lydia Njenga, Geoffrey Kamau, et Mark E. Casida, “Density-Functional Study of Lumininescence in Polypyridine Ruthenium Complexes,” J. Photochem. and Photobiol. A 276, 8 (2014). Cet article a proposé une indice orbitalaire de temps de luminescence pour les complexesde ruthénium. Cependant cet article n’était limité qu’à quelques mnolecules. Afin d’avoir une théorie plus fiable et donc potentiellement plus utile, il faudra tester l’indice de luminescence sur beaucoup plus de molécules. Ayant établi le protocol, il était “évident” mais toujours un défi de le tester sur encore une centaine de molécules pour démonter ou infirmer l’indice proposée. Pour ce faire, j’ai examainé les 98 pages de la Table I de A. Juris, V. Balzani, F. Bargelleti, S. Campagna, P. Belser, et A.V. Zelewsky, “Ru(II) polypyridine complexes: Photophysics, photochemistry, electrochemistry, and chemiluminescence,” Chem. Rev. 84, 85 (1988) et j’ai extrait un nombre important de données susceptibles à comparaison avec les résultats des calculs de la théorie de la fonctionelle de la densité (DFT) et la DFT dépendante du temps (TD-DFT). Comme les résultats étaient suffisament encourageant, le modèle DFT était examiné de plus près avec la méthode d’une théorie de champs de ligands (LFT) à la base de la densité des états partielle (PDOS). Ainsi j’ai pu tester l’indice de luminescence proposée précédement par laméthode PDOS-LFT et j’ai trouvé des difficultés avec l’indice initialement proposée. Par contre, nous avons pu proposer une nouvelle indice de luminescence qui, à quelques exceptions près, a une corrélation linéaire avec une barrière énergétique moyenne pour l’état triplet excité dérivée à partir des données experimentales. À l’avenir nous pouvons proposer une investigation plus directe de la barrière sur la surface triplet excité pour remplacer la valeur approximative déduite de l’expérience. Puis nous voulons voir sinotre indice de luminescence s’appliquent aux cas des complexes d’iridium<br>This thesis is part of the Franco-Kenyan project ELEPHOX (ELEctrochemicaland PHOto Properties of Some Remarkable Ruthenium and Iron CompleXes)project. In particular, it focused on the continuation of the work ofC. Muhavini Wawire, Damien Jouvenot, Fréd erique Loiseau, Pablo Baudin,Sébastien Liatard, Lydia Njenga, Geoffrey Kamau, and Mark E. Casida,“Density-Functional Study of Lumininescence in Polypyridine RutheniumComplexes,” J. Photochem. and Photobiol. A 276, 8 (2014). That paperproposed a luminescence index for estimating whether a ruthenium complexwill luminesce or not. However that paper only tested the theory ona few molecules. In order for the theory to have a significant impact, itmust be tested on many more molecules. Now that the protocol has beenworked out, it was a straightforward but still quite challenging matter todo another 100 or so molecules to prove or disprove the theory. In order todo so, I went through the 98 pages of Table I of A. Juris, V. Balzani, F.Bargelleti, S. Campagna, P. Belser, and A.V. Zelewsky, “Ru(II) polypyridinecomplexes: Photophysics, photochemistry, electrochemistry, and chemiluminescence,”Chem. Rev. 84, 85 (1988) and extracted data suitable for comparingagainst density-functional theory (DFT) and time-dependent (TD-)DFT.Since the results were sufficiently encouraging, the DFT model was examinedin the light of partial density of states ligand field theory (PDOS-LFT) andthe previously proposed luminescence indices were tested. In fact, the originallyproposed indices were not found to be very reliable but we were able topropose a new luminescence index based upon much more data and in analogywith frontier-molecular orbital ideas. Except for a few compounds, this index provides a luminescence index with a good linear correlation with anexperimentally-derived average excited-state activation energy barrier. Futurework should be aimed at both explicit theoretical calculations of thisbarrier for ruthenium complexes and extension of the luminescence indexidea to iridium complexes
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Lee, Jung Sup. "SPECTROSCOPY AND STRUCTURES OF METAL-CYCLIC HYDROCARBON COMPLEXES." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_diss/39.
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Metal-cyclic hydrocarbon complexes were prepared in a laser-vaporization molecular beam source and studied by single-photon zero electron kinetic energy (ZEKE) and IR-UV resonant two-photon ionization (R2PI) spectroscopy. The ionization energies and vibrational frequencies of the metal complexes were measured from the ZEKE spectra. Metal-ligand bonding and low-lying electronic states of the neutral and ionized complexes were analyzed by combining the ZEKE measurements with density functional theory (DFT) calculations. In addition, C-H stretching frequencies were measured from the R2PI spectra.
In this dissertation, metal complexes of 1, 3, 5, 7-cyclo-octatetraene (COT), toluene, p-xylene, mesitylene, hexamethylbenzene, biphenyl, naphthalene, pyrene, perylene, and coronene were studied. For each metal-ligand complex, different effects from the metal coordination have been identified. Although free COT is a nonaromatic molecule with a tub-shaped structure, the group III transition metal atoms (Sc, Y, and La) donate two electrons to a partially filled π orbital of COT, making the ligand a dianion. As a result, metal coordination converts COT into a planar, aromatic structure and the resulting complex exhibits a half-sandwich structure. For the Sc(methylbenzene) complexes, the benzene rings of the ligands are bent and the π electrons are localized in a 1, 4-diene fashion due to differential Sc binding with the carbon atoms of the rings. Due to differential metal binding, the degenerate d orbitals split and the Sc-methylbenzene complexes prefer the low-spin ground electronic states. In addition, as the number of methyl group substituents in the ligand increases, the ionization energies (IEs) of the Sc-methylbenzene complexes decrease. However, Ti, V, or Co coordination does not disrupt the delocalized π electron network within the carbon skeleton in the high-spin ground states of the metal complexes. For group VI metal (Cr, Mo, and W)-bis(toluene) complexes, methyl substitution on the benzene ring yields complexes with four rotational conformers of 0°, 60°, 120°, and 180° conformation angles between two methyl groups. In addition, variable-temperature ZEKE spectroscopy using He, Ar, or their mixtures has determined the totally eclipsed 0° rotamer to be the most stable. When there are two equivalent benzene rings, the metal (Ti, Zr or Hf) binds to both the benzene rings of biphenyl, or the metal (Li) binds to one of the benzene rings of naphthalene. On the other hand, the metal (Li) favors the ring-over binding site of the benzene ring with a higher π electron content and aromaticity in pyrene, perylene, and coronene.
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Braden, Dale Andrew. "Part 1--Elucidation of the structure and properties of 19-electron organometallic complexes using density functional theory ; Part 2--Solvent cage effects--identification of solvent and solute characteristics which influence the recombination efficiency of geminate radicals /." view abstract or download file of text, 2000. http://wwwlib.umi.com/cr/uoregon/fullcit?p9963443.
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Thesis (Ph. D.)--University of Oregon, 2000.<br>Typescript. Includes vita and abstract. Includes bibliographical references (leaves 159-176). Also available for download via the World Wide Web; free to University of Oregon users. Address:http://wwwlib.umi.com/cr/uoregon/fullcit?p9963443.
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Chen, Shentan. "Theoretical studies on oxidative addition of ammonia to iridium complexes and metathesis reactions of triple bonds involving tungsten, molybdenum, carbon and nitrogen employing density functional theory." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view.cgi?acc%5Fnum=osu1245255909.
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Georgiev, Valentin. "Reaction Mechanisms of Metalloenzymes and Synthetic Model Complexes Activating Dioxygen a computational study /." Doctoral thesis, Stockholm : Department of Physics, Stockholm University, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-30706.
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Diss. (sammanfattning) Stockholm : Stockholms universitet, 2009.<br>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: In progress, Paper 5: In progress. Härtill 5 uppsatser.
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Wu, Yin [Verfasser], Notker [Akademischer Betreuer] Rösch, and Bernhard [Akademischer Betreuer] Rieger. "Hydrosilylation of Alkenes Catalyzed by Bis-N-Heterocyclic Carbene Rh(I) Complexes: A Density Functional Theory Study / Yin Wu. Gutachter: Notker Rösch ; Bernhard Rieger. Betreuer: Notker Rösch." München : Universitätsbibliothek der TU München, 2014. http://d-nb.info/1071947990/34.
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Gowda, V. (Vasantha). "Experimental and computational magnetic resonance studies of selected rare earth and bismuth complexes." Doctoral thesis, Luleå University of Technology, 2017. http://jultika.oulu.fi/Record/isbn978-91-7583-948-6.
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Abstract
The rare-earth elements (REEs) and bismuth, being classified as the ‘most critical raw materials’ (European Raw Materials Initiatives, 2017), have a high economic importance to the EU combined with a high relative supply risk. REEs are highly important for the evolving technologies such as clean-energy applications, high-technology components, rechargeable batteries, permanent magnets, electric and hybrid vehicles, and phosphors monitors.
This scientific research work aims at building a fundamental knowledge base concerning the electronic/molecular structure and properties of rare-earth element (REE) and bismuth complexes with dithiocarbamate (DTC) and 1,10-phenanthroline (PHEN) by employing state-of-the-art experimental techniques such as nuclear magnetic resonance (NMR) spectroscopy and X-ray diffraction (XRD) techniques together with ab initio quantum mechanical computational methods. This combination of methods has played a vital role in analysing the direct and significant effect of the heavy metal ions on the structural and magnetic resonance properties of the complexes, thereby, providing a framework of structure elucidation. This is of special importance for REEs, which are known to exhibit similar chemical and physical properties. The objectives of the work involve i) a systematic investigation of series of REE(III) as well as bismuth(III) complexes to get a profound understanding of the structure-properties relationship and ii) to find an appropriate theoretical modelling and NMR calculation methods, especially, for heavy metal systems in molecular and/or solid-state. This information can later be used in surface interaction studies of REE/bismuth minerals with DTC as well as in design and development of novel ligands for extraction/separation of metal ions.
The REE(III) and bismuth(III) complexes with DTC and PHEN ligands have all provided a unique NMR fingerprint of the metal centre both in liquid and solid phase. The solid-state ¹³C and ¹⁵N NMR spectra of the diamagnetic REE(III) and bismuth(III) complexes were in accord with their structural data obtained by single crystal XRD. The density functional theory (DFT) methods were used to get complementary and refined structural and NMR parameters information for all diamagnetic complexes in the solid-state. The relativistic contributions due to scalar and spin-orbit correlations for the calculated ¹H/¹³C/¹⁵N chemical shifts of REE complexes were analysed using two-component zeroth-order regular approximation (ZORA)/DFT while the ‘crystal-lattice’ effects on the NMR parameters were calculated by combining DFT calculations on molecular and periodic solid-state models. The paramagnetic REE complexes display huge differences in their ¹H and ¹³C NMR spectral patterns. The experimental paramagnetic NMR (pNMR) chemical shifts, as well as the sizable difference of the ¹H and ¹³C NMR shifts for these isoelectronic complexes, are well reproduced by the advanced calculations using ab initio/DFT approach. The accuracy of this approach is very promising for further applications to demanding pNMR problems involving paramagnetic f-block elements.
The results presented in this thesis demonstrate that a multidisciplinary approach of combined experimental NMR and XRD techniques along with computational modelling and property calculations is highly efficient in studying molecular complexes and solids containing heavy metal systems, such as rare-earths and bismuth.
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Noack, Holger. "Biomimetic Iron Complexes involved in Oxygenation and Chlorination : A Theoretical Study." Doctoral thesis, Stockholms universitet, Fysikum, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-38197.
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Biomimetic chemistry is directed towards the simulation of enzymatic reactivity with synthetic analogues. In this thesis a quantum chemical method has been employed to study the mechanism of highly reactive iron-oxo complexes involved in oxygenation and chlorination of organic substrates. The aim of this research is to gain greater understanding for the reactivity paradigm of the iron-oxo group. One reaction deals with the conversion of cyclohexane into adipic acid, a key chemical in industrial chemistry, catalyzed by an iron(II)-porphyrin complex in the presence of dioxygen. This process constitutes a ’green’ alternative to conventional adipic acid production, and is thus of great interest to synthetic chemistry. Another reaction investigated herein regards the selective chlorination observed for a new group of non-heme iron enzymes. With help of theoretical modeling it was possible to propose a mechanism that explains the observed selectivity. It is furthermore demonstrated how a biomimetic iron complex simulates the enzymatic reactivity by a different mechanism. Other topics covered in this thesis regard the structure-reactivity relationship of a binuclear iron complex and the intradiol C-C bond cleavage of catechol catalyzed by an iron(III) complex.<br>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Submitted. Paper 2: Accepted. Paper 3: Submitted.
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Yang, Xiaofan. "Application of density functional theory on water oxidation catalysts and a combined experimental/theoretical study of carbene complexes (arene)M=C(Ph2P=NPh)2 (M ruthenium and osmium) /." [Bloomington, Ind.] : Indiana University, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3344555.
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Thesis (Ph. D.)--Indiana University, Dept. of Chemistry, 2008.<br>Title from PDF t.p. (viewed Oct. 7, 2009). Source: Dissertation Abstracts International, Volume: 70-02, Section: B, page: 1022. Advisers: Mu-Hyun Baik; Kenneth G. Caulton.
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D'Acchioli, Jason S. "On the nature of the electronics structure of metal-metal quadruply bonded complexes." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1126621699.
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Thesis (Ph. D.)--Ohio State University, 2005.<br>Title from first page of PDF file. Document formatted into pages; contains xii, 286 p.; also includes graphics (some col.). Includes bibliographical references (p. 273-286). Available online via OhioLINK's ETD Center
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Shen, Jingyi. "Density functional theory study on the interstitial chemical shifts of main-group-element centered hexazirconium halide clusters; synthetic control of speciation in [(Zr6ZCl12)] (Z = B, C)-based mixed ligand complexes." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/2444.
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The correlation between NMR chemical shifts of interstitial atoms and electronic structures of boron- and carbon-centered hexazirconium halide clusters was investigated by density functional theory (DFT) calculation. The influences of bridging halide and terminal ligand variations on electronic structure were examined respectively. Inverse proportionality was found between the chemical shifts and the calculated energy gaps between two Kohn-Sham orbitals of t1u symmetry, which arose from the bonding and antibonding interaction between the zirconium cage bonding orbitals and the interstitial 2p orbitals. Chemical shielding properties of the interstitial atoms were calculated with Gauge Including Atomic Orbital (GIAO) method. Stepwise ligand substitution of terminal chlorides on [(Zr6CCl12)Cl6]4-cluster by tri(n-butyl)-phosphine oxide (Bu3PO) was conducted with the aid of TlPF6. Composition of the reaction mixtures was analyzed by use of both 13C and 31P NMR. A preliminary scheme for synthesis and separation of [(Zr6CCl12)Cl6-x(Bu3PO)x]x-4 (x = 3 ?? 5) mixture based on solubility difference was reevaluated. Three 1,10-phenanthroline based bidentate ligands, namely, 2,9-Bis(diphenyl-phosphinyl)-1,10-phenanthroline, 2,9-Bis(diethoxyphosphoryl)-1,10-phenanthroline, and 2,9-Bis(di-n-butoxyphosphoryl)-1,10-phenantholine, were synthesized for bridge-chelating the hexazirconium clusters. Coordination chemistry of these ligands with the [Zr6BCl12] and [Zr6CCl12] clusters was subject to preliminary investigation.
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Asiri, Yazeed. "Ab Initio and Semi-Empirical Calculations of Cyanoligated Rhodium Dimer Complexs." Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/etd/3177.
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Molecular modeling, using both ab initio and semi-empirical methods has been undertaken for a series of dirhodium complexes in order to improve the understanding of the nature of the chemical bonding in this class of homogeneous catalysts. These complexes, with carboxylamidate and carboxylate ligands, are extremely functional metal catalysts used in the synthesis of pharmaceuticals and agrochemicals. The X-ray crystallography shows anomalies in the bond angles that have potential impact on understanding the catalysis. To resolve these issues, minimum energy structures of several examples (e.g. Rh2(NHCOCH3)4, Rh2(NHCOCH3)4NC, Rh2(CO2CH3)4, Rh2(CO2CH3)4NC, Rh2(CHO2)4, and Rh2(CHO2)4NC) were calculated using Hatree-Fock and Density Functional Theory/B3LYP with the LANL2DZ ECP (Rh), and cc-pVDZ (all other atoms) basis sets.
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Lima, Leidiana de Sousa. "Estudo da interação entre o oxigênio molecular com complexos tetraazamacrociclos de cobalto utilizando a Teoria do Funcional da Densidade." Universidade Federal do Maranhão, 2016. http://tedebc.ufma.br:8080/jspui/handle/tede/1568.
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Previous issue date: 2016-09-02<br>Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão (FAPEMA)<br>This paper presents the results obtained by quantum study applying the functional theory of density - DFT and using the B3LYP functional to verify the electronic structures of Tetraazamacrociclos Cobalt (CoN4) and their interactions with oxygen through Griffith adsorption models (Side-on) and Pauling (End-on). The initial structures of Porphyrin Cobalt complex – CoP, Octametilporfirina Cobalt - CoOMP, Tetrametilporfirina Cobalt - CoTMP, tetraaza [14] annulene Cobalt - CoTAA and Dibenzotetraaza [14] annulene Cobalt - CoDBTAA were obtained from GaussView program and optimization the geometry and charge distribution of the structures, as well as their interactions with molecular oxygen were carried out using the Gaussian 09 program. The results shows that the structure of the macrocycle ligands influence O2 binding capacity to cobalt. In evaluating the interaction with oxygen, porphyrin cobalt and its derivatives showed better evidence against group tetraaza [14] annulene, for interaction with molecular oxygen due to weakening of the bond in the O2 molecule characteristic enhanced by data from Mulliken charge. Therefore, the order of interaction presented by the studied complexes is CoTMP, CoOMP, CoP, CoDBTAA and CoTAA in End-on model and CoP CoOMP, CoTMP, CoDBTAA and CoTAA in side-on model.<br>Este trabalho apresenta os resultados obtidos por meio estudo quântico aplicando a Teoria do Funcional da Densidade – DFT e usando o funcional B3LYP para verificar as estruturas eletrônicas de Tetraazamacrociclos de Cobalto (CoN4) e suas interações com o oxigênio por meio dos modelos de adsorção de Griffith (Side-on) e Pauling (End-on). As estruturas iniciais dos complexos Porfirina de Cobalto - CoP, Octametilporfirina de Cobalto - CoOMP, Tetrametilporfirina de Cobalto - CoTMP, Tetraaza[14]anuleno de Cobalto - CoTAA e Dibenzotetraaza[14]anuleno de Cobalto - CoDBTAA foram obtidas do programa GaussView e a otimização das geometrias e a distribuição de carga das estruturas, bem como as suas interações com o oxigênio molecular, foram realizadas com o uso do programa Gaussian 09. Os resultados obtidos comprovam que a estrutura dos ligantes do macrociclo influência a capacidade de ligação do O2 ao cobalto. Na avaliação da interação com oxigênio, a Porfirina de Cobalto e seus derivados mostraram uma melhor evidência, frente ao grupo Tetraaza[14]anuleno, para a interação com o oxigênio molecular devido ao enfraquecimento da ligação na molécula de O2, característica reforçada pelos dados provenientes da carga Mulliken. Portanto, a ordem de interação apresentada pelos complexos estudados é CoTMP, CoOMP, CoP, CoDBTAA e CoTTA no modelo End-on e CoP, CoOMP, CoTMP, CoDBTAA e CoTAA no modelo side-on.
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Otten, Brooke Michelle. "Computational and Experimental Studies of the Photoluminescence, Reactivity and Structural Properties of d10 and d8 Metal Complexes." Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1505232/.
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Computational chemistry has gained interest as a characterization tool to predict photoluminescence, reactivity and structural properties of organic and transition metal complexes. With the rise of methods including relativity, these studies have been expanded to the accurate modeling of luminescence spectra of complexes with considerable spin-orbit splitting due to heavy metal centers as well as the reaction pathways for these complexes to produce natural products such as hydrogen gas. These advances have led to the synthesis and utility of more effective catalysis as well as the development of more effective organic light emitting diodes (OLEDs) through the incorporation of organometallic complexes as emitters instead of typical organic emitters. In terms of significant scientific advancement presented in this work is in relation to the discovery of significant spin-orbit splitting in a gold(I) alkylphosphine complex, where the splitting results in the states that emit in different colors of the visible region of the electromagnetic spectrum. This work also reveals the discovery both computationally and experimentally, of a genuine polar-covalent bond between two-closed shell metals. This work highlights a complex with an incredibly short gold(I) – copper(I) intermetallic distance leading to a vibrational frequency and dissociation energy that is on par with those of other systems with single-bonded metal centers. Lastly, this work outlines a strategy for the production of hydrogen gas through the use of trinuclear cyclic coinage metal complexes as catalysis to split hydrohalic acids.
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Afaneh, Akef. "Computational investigations of the electronic structure of molecular mercury compounds: ion-selective sensors." Springer International Publishing AG, 2012. http://hdl.handle.net/1993/30661.
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This thesis presents the basic concepts of electronic structure theory and the chemical properties of mercury. The theoretical foundation of DFT and the consequences of relativity are also introduced. The electronic structure of Hg(II) ions, [Hg(L)n(H2O)m]q (L = HO-, Cl-, HS-, S2-) has been studied. We show, in this thesis, that the charge transfer (that is calculated from the hard-soft-acid-base principle (Pearson’s principle)), the total NBO charge and the interaction energies are strongly correlated. Our studies indicate the effect of the solvent on the global electrophilicity, the charge transfer and consequently the interaction strength between Hg(II) and ligand L. The formation constants, logK, of Hg2+−complexes are calculated. The procedure that we follow in this thesis to calculate the formation constants, logK’s, are in good agreement with the extrapolated experimental values. We introduce and explain why it is important adding water molecules explicitly during the calculations of the logK. The recommended logK value of HgS is 27.2. We examined two different types of organic compounds as sensors for heavy metal ions: lumazine (Lm) and 6-thienyllumazine (TLm). We found that the simple calculation of pKa values using DFT methods and implicit solvent models failed to reproduce the experimental values. However, calculated orbital energies and gas phase acidities both indicate that the compound TLm is inherently more acidic than the parent species Lm. We demonstrate that: (1) we need to take in our consideration the population of each tautomer and conformer during the calculations of the pKa values, and (2) thienyl group has indirect effect on the acidity of the proton on N1 in the uracil ring. Last but not least, the fluorescence spectrum of the sensors (L) and their [(L)nM(H2O)m]2+ complexes (L = Lumazine (Lm) and 6-thienyllumazine (TLm) and M = Cd2+and Hg2+) are calculated using time dependent DFT (TDDFT). The results show that TDDFT is in good agreement with experimental results. This chapter provides a new concept in the design of fluorescence turn-on/off sensors that has wider applicability for other systems. Finally, we provide a summary of the works compiled in this thesis and an outlook on potential future work.<br>October 2015
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Ibrahim, Mohamad. "Étude de la réactivité du dimère hétéronucléaire PdTi avec le monoxyde de carbone et du titane atomique avec CO et H2O en matrice d’argon et par spectroscopie vibrationnelle FTIR Spectra and structures of the Pdm-CO complexes: An infrared matrix isolation and density functional study Infrared Spectroscopy and Density Functional Theory Investigations of PdTi Heterodimer Reactivity with Carbon Monoxide Isolated in Solid Argon." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS643.
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Le sujet de cette thèse est l'étude de la réactivité de métaux de transition avec les ligands CO et H2O en utilisant la technique d’isolation en matrices d’argon à 12 K et la spectroscopie infrarouge à transformée de Fourier. Nous avons étudié la réaction du dimère hétéronucléaire PdTi avec le CO et nous avons pu identifier les molécules PdTi-CO, TiPd-CO, PdTi(CO)2 et PdTi(CO)3. L’irradiation dans le visible permet de convertir la molécule PdTi-CO avec un CO lié au Ti à la molécule TiPd-CO avec un CO lié au Pd. Dans la deuxième partie de cette thèse nous avons étudié la réaction du titane atomique avec deux ligands différents, le CO et H2O. Cette réaction est spontanée et nous avons ainsi caractérisé les molécules HTiOH-CO et HTiOH-(CO)2, essentiellement à l’aide des molécules isotopiques du CO et de H2O.Des calculs ont été effectués avec la théorie de la fonctionnelle de la densité (DFT). La comparaison entre les données théoriques et expérimentales nous a permis de déterminer les paramètres géométriques et électroniques des espèces étudiées<br>The purpose of this thesis is the study of transition metal atoms reactivity with the CO and H2O ligands using argon matrix isolation at 12 K and the Fourier Transform Infrared Spectroscopy. We have studied the reaction between the heteronuclear PdTi dimer with CO and we have identified the PdTi-CO, TiPd-CO, PdTi(CO)2, and PdTi(CO)3 molecules. Irradiation in the visible leads to the conversion from PdTi-CO with a Ti-CO bond to TiPd-CO with a Pd-CO bond. In the second part of this thesis, we have studied the reaction between the atomic titanium and the CO and H2O ligands. This is a spontaneous reaction and we have characterized the HTiOH-CO and HTiOH-(CO)2 molecules essentially with the help of the isotopic CO and H2O molecules. Calculations have been made with the density functional theory (DFT). The comparison between theoretical and experimental data allowed us to determine the geometric and electronic parameters of the studied species
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Berger, Gilles. "Synthesis of chiral vicinal diamines and in vitro anticancer properties of their platinum(II) coordinates." Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209376.
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15N-based nuclear magnetic resonance techniques are considered very powerful to study the molecular properties of platinum-containing anticancer agents, these properties being responsible for the efficacy of the compounds, but also for the understanding of resistance mechanisms and toxicity. Therefore, the first part of the present work aimed to develop a new method for synthesizing 15N-labeled, chiral platinum compounds. A theoretical discussion on the nucleophilic ring-opening of aziridines has also been envisaged, rationalizing an interesting regiochemistry question. Indeed, a surprising inversion of regiochemistry arose during the development of the above-mentioned synthetic pathway, and density functional theory calculation brought a rational framework to the experimental findings.<p><p>Infrared spectroscopy probes the global chemical composition of a sample and has been used to produce a snapshot of cancer cells contents after treatment with platinum coordinates. Indeed, in vitro studies focused here on the use of modern spectroscopic methods to fingerprint the cellular impact of platinum complexes. These drug signatures help to classify and select promising compounds. It makes no doubt that such systemic approaches for compound discovery are helpful technologies. Also, we made the use of the COMPARE algorithm from the NCI, which analyzes similarity between any active compounds previously tested by the NCI large scale in vitro screening program of anticancer agents. <p><p>The last chapter aimed to study the interactions between a series of platinum coordinates and DNA. Binding mode to telomeric-like sequences and binding kinetics to genomic-like sequences were assessed to investigate any differences between the compounds and to gain insight into structure-activity relationships. <p><br>Doctorat en Sciences biomédicales et pharmaceutiques<br>info:eu-repo/semantics/nonPublished
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Hamid, Firas Abdel. "Surfaces d’alliages métalliques complexes : nanostructures et croissance moléculaire." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0155.
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Les alliages métalliques complexes (CMAs) sont des intermétalliques dont la maille élémentaire est caractérisée par un grand nombre d’atomes ainsi qu’une sous-structure en agrégats de haute symétrie. Les quasicristaux et leurs approximants périodiques font partie de cette classe de matériaux. Ici, nous avons étudié la structure atomique et électronique de la surface (100) d’un composé cage Ce3Pd20Si6 qui peut être également considéré comme un CMA. Sa structure est décrite par un assemblage de cages - Pd12Si6 et Pd16 – enfermant les atomes de Ce. La surface est analysée en utilisant des méthodes expérimentales d’analyse sous ultravide comme la photoémission, la diffraction d’électrons et la microscopie à effet tunnel (STM), ainsi que des méthodes de simulations atomistiques basées sur la théorie de la fonctionnelle de la densité (DFT). On trouve que la surface se forme par troncature du volume en des plans spécifiques qui conservent le sous-réseau de cage de type Pd12Si6, avec des atomes de Pd supplémentaires qui rendent la surface plus compacte. L’analyse de la fonction de localisation électronique et des volumes et charges de Bader montrent que, bien que le système soit clairement métallique, la structure de la surface est influencée par les interactions entre les atomes de Pd et Si formant les cages Pd12Si6. Du fait de la préservation de ces cages, la surface présente une nanostructuration intrinsèque, de périodicité légèrement inférieure au nanomètre. Cette surface est ensuite utilisée comme patron pour essayer de former des films moléculaires auto-organisés. Des premiers résultats sont présentés concernant l’auto-assemblage de C60 et de son dérivé (PTBC) sur différents substrats, Ce3Pd20Si6(100) mais aussi les surfaces d’ordre 5 des phases icosaédriques i-AlCuFe et i-AgInYb ainsi que les surfaces hexagonales simples Cu(111) et Au(111). Des modèles simples sont proposés pour décrire les structures formées par les PTBC sur Cu(111) et Au(111). Les dépôts de C60 sur la surface Ce3Pd20Si6(100) conduit à la formation de deux domaines rotationnels de structure hexagonale très faiblement organisés, alors que PTBC donne des films amorphes. Pour PTBC déposées sur les surfaces quasicristallines, on trouve dans les deux cas que les molécules sont orientées selon les axes de symétrie du substrat à bas taux de couverture. L’accord de symétrie molécules/substrat est essentiel. Lorsque la monocouche est saturée, le film est soit amorphe sur i-AlCuFe soit quasipériodique sur i-AgInYb mais avec beaucoup de désordre<br>Complex metallic alloys (CMAs) are intermetallics with a unit cell characterized by a large number of atoms and a substructure of atomic clusters of high symmetry. Quasicrystals and their periodic approximants are part of this class of materials. Here, we have investigated the atomic and electronic structure of the (100) surface of a cage compound Ce3Pd20Si6 which can be also considered as a CMA. The assembly of Pd12Si6 and Pd16 cages in which guest Ce atoms are located describes its structure. The surface is analyzed using experimental methods under ultrahigh vacuum as well as atomistic simulations based on density functional theory (DFT). The surface forms at corrugated planes of the bulk structure that preserve intact the Pd12Si6 cages, with additional Pd surface atoms. It is concluded that despite this Pd-based cage compound being clearly metallic, stronger interactions between Pd and Si atoms on the host cage structure significantly influence its surface structure. Due to the cage preservation, the surface presents an intrinsic nanostructuration with a periodicity slightly less than one nanometer. This surface is further used as a pattern in an attempt to form self-organized molecular films. First results are presented concerning the self-assembly of C60 and its derivative (PTBC) on different substrates, including Ce3Pd20Si6(100) but also 5-fold surfaces of icosahedral phases i-AlCuFe and i-AgInYb and simple Cu (111) and Au (111) surfaces. Simple models are proposed to describe the structures formed by PTBC on Cu (111) and Au (111). C60 deposited on Ce3Pd20Si6(100) leads to the formation of hexagonal nanodomains,while PTBC leads to amorphous films. For PTBC deposited on quasicrystalline surfaces, preferential adsorption occurs at low coverage at 5-fold symmetric sites, dictated by symmetry matching between molecules and substrates. When the monolayer is saturated however, the film is either amorphous on i-AlCuFe or quasiperiodic on i-AgInYb, but with a large amount of disorder
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Petrović, Predrag. "Experimental and theoretical investigations of intermetallic in transition metal coordination and organometallic complexes." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAF029.
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Ce travail de thèse démontre l’importance d’intégrer des outils théoriques à des observations expérimentales dans le but d’étudier le rôle des interactions non-covalentes et plus précisément de la dispersion dans la chimie des métaux de transition. Plusieurs thèmes ont ainsi été abordés comme les interactions d’empilement entre chélates de métaux de transition à l’état solide; l’influence de la chiralité sur l’oligomérisation en solution de complexes plans carrés de Rh(I) isonitrile; la stabilité et inactivité inhabituelles de complexes de type cis-platine en solution concentrée. Les résultats obtenus par titration calorimétrique isotherme ont permis d’évaluer la capacité de méthodes théoriques à reproduire avec précision les résultats expérimentaux. Les calculs ont démontré qu’un traitement théorique approprié des effets de la dispersion et de la solvatation, donne des valeurs cohérentes avec les résultats expérimentaux. Cependant, des améliorations supplémentaires sont nécessaires<br>This thesis has shown the importance of integration of theoretical calculations and experimental investigations in studying the role of non-covalent interactions and particularly dispersion interactions in transition metal chemistry. Several subjects were addressed, such as stacking interactions of chelates in transition metal complexes in solid state, influence of chirality on the oligomerization of Rh(I) isonitrile complexes in solution and the stability of the cis-platin type complexes in concentrated solutions. Isothermal titration calorimetry proved to be very useful in the studies by providing accurate experimental data on the thermochemistry of addressed processes. This data was used to gauge the ability of the theoretical methods to accurately reproduce the experimental results. Calculations have shown that the proper treatment of dispersion effects and solvation by theoretical models gives values in relatively good agreement with experiments, but further improvements are needed
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Meyer, Jörg, Anja Wadewitz, Lokamani, et al. "Molecules for organic electronics studied one by one." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-138788.
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The electronic and geometrical structure of single difluoro-bora-1,3,5,7-tetraphenyl-aza-dipyrromethene (aza-BODIPY) molecules adsorbed on the Au(111) surface is investigated by low temperature scanning tunneling microscopy and spectroscopy in conjunction with ab initio density functional theory simulations of the density of states and of the interaction with the substrate. Our DFT calculations indicate that the aza-BODIPY molecule forms a chemical bond with the Au(111) substrate, with distortion of the molecular geometry and significant charge transfer between the molecule and the substrate. Nevertheless, most likely due to the low corrugation of the Au(111) surface, diffusion of the molecule is observed for applied bias in excess of 1 V<br>Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Meier, Matthias. "Influence de la liaison chimique sur la structure des surfaces d'alliages métalliques complexes." Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0257/document.
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Un alliage métallique complexe est un intermétallique dont la maille est constituée d'un nombre important d'atomes et dont la structure peut être souvent décrite comme un empilement de motifs d'atomes reliés par des liaisons de type covalent. Al5Co2 est l'un de ces composés et est un catalyseur potentiel pour la semi-hydrogénation d'acétylène. L'influence de la structure tridimensionnelle sur les surfaces bidimensionnelles et donc la réactivité est étudiée. Pour se faire, le système massif est analysé en utilisant la DFT afin d'éclaircir ses propriétés thermodynamiques, électroniques et vibrationnelles. Les valeurs calculées, expérimentales et celles de la littérature sont en bon accord. La structure des surfaces de bas indice, (001), (100) et (2-10) est étudiée. Une combinaison de techniques d'analyse de surface sous ultra-vide - LEED, STM - et de DFT est utilisée pour les déterminations structurales. Les résultats indiquent que: (i) la structure des surfaces dépend des conditions de préparation, comme la température de recuit, (ii) la structure des surfaces peut être interprétée comme étant constituée de motifs tronqués où certaines liaisons de type covalent sont brisées. Les sites et les énergies d'adsorption des molécules impliquées dans la réaction de semi-hydrogénation sont calculés pour les trois surfaces. Pour les sites favorables, des distances spécifiques entre atomes d'hydrogène adsorbés et atomes de Co de surface et de sous-surface peuvent être observées. Les atomes de Co de sous-surface ont un caractère donneur d'électrons, stabilisant les atomes adsorbés en surface. En se basant sur des calculs NEB, de possibles chemins réactionnels sur la surface (2-10) sont proposés. L'activité calculée est similaire à celle obtenue pour la surface d'Al13Co4, qui est considérée comme un bon catalyseur. La sélectivité - la compétition entre la désorption d'éthylène et son hydrogénation en éthyle - est discutée<br>A complex metallic alloy is an intermetallic with a large unit cell and whose structure can often be seen as a stacking of motifs of strongly covalent-like bonded atoms. Al5Co2 is such a compound and is a potential catalyst for the semi-hydrogenation of acetylene. The influence of the 3-dimensional structure on 2-dimensional surfaces is investigated. Therefore, the bulk system is analysed using DFT to gain insight in the thermodynamic, electronic and vibrational properties. Good agreements between calculated results, experimental ones and results found in the literature are obtained. The low index (001), (100) and (2-10) surfaces are investigated. A combination of surface analysis techniques under ultra high vacuum - LEED, STM - and DFT calculations is used for the structural investigations. The results show that: (i) the surface structure depends on the preparation conditions, such as the annealing temperature, (ii) the surface structure can be interpreted as truncated motif parts, where the covalent-like bonds are broken. Adsorption sites and energies of molecules involved in the semi-hydrogenation reaction are calculated for all three surfaces. For favourable adsorption sites, specific distances of adsorbed H atoms with Co surface and subsurface atoms are observed. These Co subsurface atoms have an electron donor character, stabilising the adsorbed atoms at the surface. Based on NEB calculations, possible reaction paths on the (2-10) surface are proposed. The calculated activity is similar to the one obtained for the Al13Co4 surface, which is considered a good catalyst. The selectivity - the competition between desorption of ethylene and its further hydrogenation - is discussed
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Meyer, Jörg, Anja Wadewitz, Lokamani, et al. "Molecules for organic electronics studied one by one." Royal Society of Chemistry, 2011. https://tud.qucosa.de/id/qucosa%3A27781.
Full textAbstract:
The electronic and geometrical structure of single difluoro-bora-1,3,5,7-tetraphenyl-aza-dipyrromethene (aza-BODIPY) molecules adsorbed on the Au(111) surface is investigated by low temperature scanning tunneling microscopy and spectroscopy in conjunction with ab initio density functional theory simulations of the density of states and of the interaction with the substrate. Our DFT calculations indicate that the aza-BODIPY molecule forms a chemical bond with the Au(111) substrate, with distortion of the molecular geometry and significant charge transfer between the molecule and the substrate. Nevertheless, most likely due to the low corrugation of the Au(111) surface, diffusion of the molecule is observed for applied bias in excess of 1 V.<br>Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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Abdulmalic, Mohammad A. "A Tailor-Made Approach for Thin Films and Monolayer Assemblies of bis(oxamato) and bis(oxamidato) Transition Metal Complexes." Doctoral thesis, Universitätsbibliothek Chemnitz, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-118769.
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The present work is dealing with the synthesis and characterization of mono- to trinuclear Cu(II)- and Ni(II)-containing bis(oxamato) and bis(oxamidato) complexes, respectively. It will be derived to which extent the spin density distribution of mononuclear complexes, determined by electron paramagnetic resonance studies experimentally and calculated by quantum mechanical calculations, can be regarded as a measure of the magnitude of magnetic superexchange interactions of corresponding trinuclear complexes. The usability of tailor-made trinuclear complexes for their deposition in form of thin film by spin-coating is described as well as the magneto-optical characterization of these thin films. It is shown, that the tailor-made functionalization of mono- to trinuclear bis(oxamidato) complexes with long alkyl chains is suited to allow these complexes to assembly in monolayers on, e.g., HOPG(0001) (highly-oriented pyrolytic graphite), whereas the functionalization of the alkyl chains with S atoms allows the generation of self-assembled monolayers on metallic gold. Furthermore it is shown, that the functionalization of mono- and trinuclear Cu(II)-containing bis(oxamato) complexes with ferrocenediyle fragments allows to modify the magnetic properties by making use of the oxidation process Fe(II)/Fe(III)<br>Die vorliegende Arbeit befasst sich mit der Darstellung und Charakterisierung ein- bis dreikerniger Cu(II)- bzw. Ni(II)-haltiger bis(oxamato) oder bis(oxamidato) Komplexe. Es wird abgeleitet, inwiefern die aus Elektronenenspinresonanz- Untersuchungen experimentell und die quantenmechanisch berechneten Spindichteverteilungen einkerniger Komplexe ein Maß für die Größe der magnetischen Superaustauschwechselwirkungen korrespondierender dreikerniger Komplexe darstellt. Die Eignung maßgeschneiderter dreikerniger Komplexe zu ihrer Überführung in dünne Filme im nm-Bereich mittels Rotationsbeschichtung auf Si/SiO2-Substraten wird beschrieben sowie die magneto-optische Charakterisierung dieser dünnen Filme. Es wird gezeigt, dass durch gezielte Funktionalisierung mit langkettigen Alkylresten ein- bis dreikernige Cu(II)-haltige bis(oxamidato) Komplexe geeignet sind, auf Substraten wie HOPG(0001) (hochorientiertes pyrolytisches Graphit) zu Monolagen zu assemblieren während die zielgerichtete Funktionalisierung der Alkylketten mit S-Atomen es ermöglicht selbst-assemblierte Monolagen auf metallischem Gold zu generieren. Zusätzlich wird beschrieben, dass durch die Funktionalisierung von ein- und dreikernigen Cu(II)-haltigen bis(oxamato) mit Ferrocendiylresten die magentischen Eigenschaften durch den Oxidationsprozess Fe(II)/Fe(III) gezielt modifiziert werden können
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Almeida, Tiago dos Reis. "Investigação teórica da agregação de complexos catiônicos de Ir (III) com potencial aplicação em LEEC\'s e OLED\'s." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/75/75134/tde-17112016-132551/.
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Nos últimos anos, complexos de irídio tem sido sugeridos para uso em materiais luminescentes, tais como diodos orgânicos emissores de luz (OLED\'s) e células eletroquímicas emissoras de luz (LEEC\'s). Suas potenciais utilidades como dispositivo é devido as suas características físico-químicas e fotofísicas, as quais são caracterizadas por tempos de vida curtos para o tripleto, estabilidade térmica, além da possibilidade de modificar a emissão sobre uma vasta gama de cores do espectro. Atualmente, muitas pesquisas tentam encontrar complexos de irídio com emissão de luz azul. No entanto, embora emissores de luz azul já tenham sido desenvolvidos, existe o problema relacionado a agregação destes complexos. Para resolver este o problema da agregação é necessário modificar a estrutura padrão do complexo com cadeias carbônicas saturadas para evitar empilhamento π-π. Experimentalmente esta é uma tarefa um tanto difícil. Dessa forma, métodos computacionais têm sido viáveis como uma abordagem para entender a estrutura e propriedades eletrônicas dos sistemas estudados. Aqui, é apresentado um estudo teórico baseado na teoria do funcional da densidade (DFT) para investigar a agregação de complexos de irídio, além de predizer como esta pode ser controlada com o uso de grupos substituintes adequados. Os cálculos foram realizados usando funcional PBE0 e conjunto de base 6-31G*, o qual provou ser adequada na descrição das propriedades do complexo. Portanto, cálculos subsequentes mostraram bons resultados, onde os estados excitados foram previstos ser de natureza predominantemente MLCT (transferência de carga do metal para o ligante) para o complexo 1 e LC (carga centrada no ligante) para o complexo 2. Alterações no ambiente químico provou ter grande influência sobre os estados excitados, onde a inclusão do solvente favoreceu a estabilidade, mantendo os estados excitados tripletos com energia entre 3.01 eV e 3.03 eV. Além disso, o uso dos grupos substituintes provou ser de grande importância para prevenir a agregação, especialmente no complexo 2, em que a partir do dímero matriz (sem substituintes) para o complexo substituído 2-1 (com metil) houve uma desestabilização da energia de interação entre os monômeros no dímero por ~ 19.78 kcal/mol, sendo que a energia do primeiro foi estimada ser -39.78 kcal/mol, enquanto o segundo foi -20 kcal/mol. Nossos resultados sugerem que a modificação do complexo torna-se bastante promissora, fazendo uso de pequenos grupos substituintes e cadeias carbônicas alifáticas, evitando assim, a agregação por empilhamento π-π.<br>In the last few years, iridium complexes have been suggested for use in luminescent materials such as organic light-emitting diodes (OLEDs) and light emitting electrochemical cells (LEECs)1-3. Their potential utility as luminescent devices is due to the physicochemical and photophysical properties, which are featured by short triplet emitting lifetimes (microseconds time scale), thermal stability, besides of possibility to tune the emission over desired spectral range. Actually, many researches try to find iridium complexes with efficient deep-blue emission, in order to use in these devices. Although many deep-blue emitters have been developed, there is still a big problem related to aggregation. So far, little has been reported about iridium complexes in solid environments, such as inorganic matrix of OLEDs and LEECs devices. To solve this issue is needed tune the structure of the complex in order to prevent the aggregation (steric hindrance), by means of drawing saturated carbon chains on the ligands to avoid the π-π stacking. Experimentally, this is a rather challenging and expensive task. In this aspect, computational methods have been performed as approaches to gain deeper insights about the structure and electronic properties of the studied systems. Here, we present a theoretical study based on density functional theory to investigate the aggregation iridium complexes, in addition to predict how this can be controlled with the use of suitable substituent groups. Calculations were performed using functional PBE0 and 6-31G* basis functions, which proved adequate in describing the properties of the complex. Therefore, subsequent calculations showed good results, where the excited state of the complex are provided, these being predominantly MLCT (metal to ligand charge transfer) nature for the complex 1 and LC (ligand centered) nature to complex 2. Changes in the chemical environment proved to have great influence on the excited states, where the inclusion of the solvent favored its stability, keeping the triplet excited states with energy between 3.01 and 3.03 eV. Furthermore, the use of substituent groups proved to be of great importance to prevent aggregation, especially in complex 2, wherein from the matrix dimer (no substituted) to complex with methyl groups there was a destabilization of the interaction energy between the monomers in the dimer by ~ 19.78 kcal / mol, being that the energy of the first was -39.78 kcal / mol, while the second was to -20 kcal / mol. Our results suggest that the modification of the complex becomes quite promising, making use of small groups and aliphatic carbon chains, thus avoiding aggregation by stacking.
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Anand, Kanika. "Surface properties of complex intermetallics at the nanoscale : from fundamentals to applications." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0239/document.
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Les alliages métalliques complexes (CMAs) sont des composés intermétalliques dont la structure cristallographique diffère de celle des alliages conventionnels par le nombre conséquent d'atomes dans la maille (jusqu'à plusieurs milliers d'atomes), généralement arrangés sous forme d'agrégats atomiques de haute symétrie. Ils sont prometteurs pour un certain nombre d'applications technologiques, en particulier les revêtements fonctionnels, en raison de leurs propriétés de surface uniques. Cette thèse a pour objectif, à la fois la détermination de la structure et des propriétés électroniques d’une surface d’un CMA de la famille des clathrates intermétalliques, et des propriétés de mouillage intrinsèques de plusieurs CMAs à base d’aluminium. Dans une première partie, nous nous sommes intéressés aux surfaces de bas indice (100) et (110) du clathrate Ba8Au5.25Ge40.75. Leurs structures atomiques et électroniques ont été déterminées en combinant des expériences de sciences des surfaces et des calculs basés sur la théorie de la fonctionnelle de la densité. La structure tridimensionnelle de Ba8Au5.25Ge40.75, formée d'un réseau de deux types de cages (structure hôte) à base de germanium et d’or, qui emprisonnent les atomes de Ba, induit une nanostructuration de la surface contrôlée par son orientation, puisque le type de cages préservées à la surface diffère pour les surfaces (100) et (110). Dans les deux cas, les atomes de Ba qui protrudent à la surface, ont un rôle primordial pour la stabilité de surface : ils assurent un transfert de charge qui sature les liaisons pendantes des atomes de germanium en surface. Dans une seconde partie, les propriétés intrinsèques de mouillage de plusieurs CMAs à base d’aluminium, ont été déterminées par une approche couplant des mesures de microscopie et des calculs ab initio. Expérimentalement, les angles de contact de gouttes de plomb (métal sonde) sur plusieurs surfaces de CMAs ont été systématiquement mesurés. Les angles précédents étant fonction, entre autres, de l’énergie interfaciale, des calculs d'énergie interfaciale ont été menés, d’une part avec un substrat d’un métal simple, Al(111), et d’autre part sur un substrat de CMA, Al13Co4(100). Les résultats obtenus mettent en évidence une forte influence de la structure de l’interface sur l’énergie interfaciale<br>Complex metallic alloys (CMAs) are intermetallic compounds possessing a large unit cell containing several tens to hundreds of atoms. Their structure can be described alternatively by the packing of highly symmetric atomic clusters. Clathrate (or cage) compounds are a new class of CMAs having a crystal structure described by a complex arrangement of covalently-bonded cages. The Ba8Au5.25Ge40.75 type-I clathrate is one such cage compound, whose bulk properties have been (and still are) extensively explored for thermoelectric applications. In fact, it is possible to tune the compound electronic structure by a fine control of its bulk composition. Regarding the properties of the Ba8Au5.25Ge40.75 surface, information remains scarce if not inexistent. However, it is known that the surfaces of CMAs often exhibit interesting surface properties. To this end, we have studied two low-index surfaces: BaAuGe(100) and BaAuGe(110) by a combination of experimental (XPS; LEED; STM) and computational (DFT) methods. Experimental results show no evidence for surface segregation and LEED patterns are consistent with (1x1) bulk terminations with no surface reconstruction. The interplay between the 3D nano-caged structure and 2D surfaces is investigated. We demonstrate that the surface structures of the two surfaces considered preserve the bulk structure cages in addition to an ordered arrangement of surface Ba atoms. The two surfaces are formed by a breakage of highly directional covalent bonds present within the framework, hence leading to destabilizing dangling bonds. Ab initio calculations show that the surface structure is stabilized through electron charge transfer from protruding Ba to surface Ge and Au atoms, saturating the dangling bonds. This charge-balance mechanism lifts the possible surface reconstruction envisaged. We reveal how the surface nanostructuration is surface orientation dependent. The results indicate that the surface electronic structure of BaAuGe(110) is impacted by the Au surface concentration. The surface models for BaAuGe(100) and BaAuGe(110) present a metallic character and low work function values, useful for further applications. Such structurally complex surfaces may also be used as templates for novel nanoscale architectures. Further in this work, we also applied the state-of-the-art surface science techniques to investigate the wetting properties of Al-based CMAs. In these experiments, chemically inert Pb element was used as a metal probe. Systematic analysis is done to find the correlation between the wetting properties and the electronic structure properties of these CMAs. Interfacial energy calculations have been performed to model the Pb/CMA interface based on few approaches reported in literature. We have tested these approaches on a moiré patterned Pb(111)/Al(111) interface. This interface is found to be controlled by geometric factors. Hence, an acquired understanding was applied to Pb deposited on Al13Co4(100) (Al-rich side) interface
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Alves, Álvaro Santos. "Estudo de magnetos moleculares através de cálculos de primeiros princípios." Niterói, 2017. https://app.uff.br/riuff/handle/1/3966.
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tese.pdf: 4548404 bytes, checksum: f3c3be1c9d5bbc0d098d37be6674bd4b (MD5)<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>Universidade Estadual de Feira de Santana<br>Neste trabalho, utilizamos cálculos de primeiros princípios baseados na Teoria do Funcional da Densidade (DFT - Density Functional Theory) para investigar a estabilidade energética e as propriedades magnéticas de compostos químicos. Foram estudados os complexos com metais de transição contendo radicais do tipo nitronilnitróxido [M(II)(Phtfac)2(NITpPy)2] [M = Co, Mn] e [M(II)(NITmPy)2(DMSO)2] [M = Cu, Ni, Co], bem como o silicato de cobre Na2Cu5(Si2O7)2. A partir do cálculo da energia total, determinamos a configuração de equilíbrio para os cinco complexos metálicos e os valores das constantes de acoplamento. Além disso, foram obtidas também as respectivas distribuições de densidade de magnetização, fundamentais para entender os mecanismos de acoplamento magnético nesse tipo de sistema. Para o silicato de cobre, cujos responsáveis pelas propriedades magnéticas são cadeias alternadas de trímeros e dímeros, calculamos a energia total das 32 configurações possíveis; determinamos o estado fundamental e as constantes de acoplamento magnético.<br>In this work we use first principles calculations based on density functional theory (DFT) to investigate the energy stability and the magnetic of chemical compounds. We studied the transition metal complexes with nitronyl nitroxide radical M(II)(P[htfac)2(NITpPy)2] [M = Co, Mn] and [M(NITmPy)2(DMSO)2] [M = Cu, Ni, Co], as well as the copper silicate Na2Cu5(Si2O7)2. By calculating the total energy, we determine the equilibrium configuration for the five metal complexes and the values of coupling constants. Moreover, we obtained their magnetization density distributions, fundamental for understanding the mechanisms of magnetic coupling in this type of system. For the copper silicate, whose magnetic properties are responsible for alternate chains of dimers and trimers, we calculate the total energy of the 32 possible configurations and determine the ground state and magnetic coupling constants.
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Zhao, Jinzhu. "Etude théorique d'oxydes nano-structurés multifonctionnels." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-00986110.
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Partant des composés ATiO3 (A=Ba, Pb, Sr) bien connus pour leurs propriétés de type ferroélectriques, il est possible de concevoir des super-réseaux de basse dimensionnalité (multi-couches, phases de type ,...) où ces propriétés peuvent être modulées en fonction de la composition, de l'épaisseur des couches mises en jeu, des contraintes aux interfaces. Nous proposons ici d'étudier par calculs de premiers principes les instabilités structurales et la dynamique de réseau pour des systèmes simples dans cette famille. En définissant clairement les zones interfaciales et de cœur des couches, et en étudiant la convergence de leurs propriétés en fonction de l'épaisseur, ce travail vise à établir des potentiels interatomiques modèles, analytiques et transférables, pour la prédiction des propriétés dynamiques et des instabilités structurales de super-réseaux étendus et/ou complexes.
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Lim, XiaoZhi. "Pincer Complexes with Isopropyl Substituents A Density Functional Theory Study." Thesis, 2011. http://hdl.handle.net/10754/229291.
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Complexes with pincer ligand moieties have garnered much attention in the past few decades. They have been shown to be highly active catalysts in several known transition metal-catalyzed organic reactions as well as some unprecedented organic transformations. At the same time, the use of computational organometallic chemistry to aid in the understanding of the mechanisms in organometallic catalysis for the development of improved catalysts is on the rise. While it was common in earlier studies to reduce computational cost by truncating donor group substituents on complexes such as tertbutyl or isopropyl groups to hydrogen or methyl groups, recent advancements in the processing capabilities of computer clusters and codes have streamlined the time required for calculations. As the full modeling of complexes become increasingly popular, a commonly overlooked aspect, especially in the case of complexes bearing isopropyl substituents, is the conformational analysis of complexes. Isopropyl groups generate a different conformer with each 120 ° rotation (rotamer), and it has been found that each rotamer typically resides in its own potential energy well in density functional theory studies. As a result, it can be challenging to select the most appropriate structure for a theoretical study, as the adjustment of isopropyl substituents from a higher-energy rotamer to the lowest-energy rotamer usually does not occur during structure optimization. In this report, the influence of the arrangement of isopropyl substituents in pincer complexes on calculated complex structure energies as well as a case study on the mechanism of the isomerization of an iPrPCP-Fe complex is covered. It was found that as many as 324 rotamers can be generated for a single complex, as in the case of an iPrPCP-Ni formato complex, with the energy difference between the global minimum and the highest local minimum being as large as 16.5 kcalmol-1. In the isomerization of a iPrPCP-Fe complex, it was found that the isopropyl substituents not only influence the calculated structure energies, but they dictate the mechanism of isomerization with the rotation of isopropyl substituents from the arrangement in the starting material complex to the arrangement in the product complex being the rate-determining step.
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Pillai, Emmanuel Dinesh. "Infrared spectroscopy and density functional theory of transition metal - nitrogen complexes." 2007. http://purl.galileo.usg.edu/uga%5Fetd/pillai%5Femmanuel%5Fd%5F200705%5Fphd.
Full textAbstract:
Thesis (Ph. D.)--University of Georgia, 2007.<br>Directed by Michael A. Duncan. For abstract see https://getd.libs.uga.edu/pdfs/pillai%5Femmanuel%5Fd%5F200705%5Fphd.pdf. Includes bibliographical references.
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Arabi, Alya A. "Density Functional Theory: Dispersion Interactions & Biological Applications." 2012. http://hdl.handle.net/10222/15525.
Full textAbstract:
London or dispersion interactions are weak van der Waals (vdW) interactions. They are important in determining the structure and properties of many chemical and biochemical systems. In this thesis, an optimizer using the nonempirical generalized gradient approximation (GGA) functional PW86+PBE+XDM, to capture van der Waals interactions, is presented. The work in this thesis covers the assessment of a variety of basis sets for their ability to reproduce accurate GGA repulsive and binding energies. Selected basis sets were then used to compute binding energies of 65 vdW complexes at equilibrium. This functional was also tested for binding energies of two sets of vdW complexes at distorted geometries. The last part deals with forces to investigate their accuracy using PW86+PBE+XDM in order to build an optimizer for vdW complexes using a nonempirical DFT method. Eventually, after confirming a high reproducibility of the optimizer on the geometries and binding energies, it was used in two biologically relevant applications. This optimizer is a unique tool to compute deformation energies with a nonempirical DFT method. The second part of this thesis covers a biologically relevant application where a conventional DFT is used. This application is related to the carrier of the genetic codes in living cells, DNA. DNA undergoes harmful mutations under external perturbations such as applied external electric fields. In this study, DNA base pairs were first mimicked by a simpler model, namely, the formic acid dimer. The effect of applied external electric fields on the geometries of the formic acid dimer is studied. The effect of these applied fields on the potential energy surface, the barrier height and the frequency of the double proton transfer in the formic acid dimer are also investigated. The study was then repeated on DNA base pairs to study the effect of an external applied electric field on the tunneling corrected rate constants of the double proton transfer reactions in AT and GC.