Academic literature on the topic 'Novel Polynuclear Complexes'

We present a simple route to multimetallic Cu^I building blocks and their interaction with organometallic polyphosphorus and -arsenic linkers affording in novel polynuclear complexes or one-dimensional coordination polymers.

Abstract The synthesis of 2-(1-(prop-2-yn-1-yl)-1H-pyrazol-3-yl)pyridine is presented. This ligand contains both, an alkynyl function being suitable for metal-carbon bond formation with electron-rich late transition metal sites, and a pyrazolylpyridine unit, which is well-known to undergo chelation reactions similar to 2,2′-bipyridine. This strategy allows building up polynuclear complexes with broad combinations of different metal sites. Two platinum alkynyl complexes were structurally characterized, and a trinuclear Ru2Pt complex was indentified by means of NMR spectroscopy and ESI mass spectrometry.

Polynuclear coordination complexes result from the interplay between the arrangement of the binding sites of a ligand, and their donor content, and the coordination preferences of the metal ion involved. Rational control of the ligand properties, such as denticity, geometry, and size, can lead to large, and sometimes predictable, polynuclear assemblies. This Alcan Award Lecture highlights our "adventures" with polynucleating ligands over the last 25 years, with examples ranging from simple dinucleating to more exotic high-denticity ligands. Complexes with nuclearities ranging from 2 to 36 have been produced, many of which have novel magnetic, electrochemical, and spectroscopic properties. Self-assembly strategies using relatively simple "polytopic" ligands have been very successful in producing high-nuclearity clusters in high yield. For example, linear "tritopic" ligands produce M9 (M = Mn(II), Fe(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II)) [3 × 3], flat grid-like molecules, which have quantum dot-like arrays of nine closely spaced metal centers in electronic communication. Some of these grids are discussed in terms of their novel magnetic and electrochemical properties, and also as multistable nanometer-scale platforms for potential molecular device behaviour. Bigger ligands with extended arrays of coordination pockets, and the capacity to self-assemble into much larger grids, are highlighted to illustrate our current and longer term goals of generating polymetallic molecular two-dimensional layers on surfaces.Key words: Alcan Award Lecture, transition metal, polynuclear, structure, magnetism, electrochemistry, surface studies, molecular device.

Novel polynuclear tungsten and molybdenum (VI) complexes with 3-hydroxypicolinic acid (HpicOH) and europium(III) [M4O12Eu(picOH)3] (M(VI) = W, Mo) were prepared by hydrothermal methods. The solid compounds were characterized by FT-IR and FT-Raman spectroscopy and elemental analysis. The photoluminescent properties of the materials were investigated, showing sensitization of the europium(III) luminescence by both the 3- hydroxypicolinate ligand and the polyoxometalate moiety

Three novel Ni complexes with the Schiff base ligand 2-methoxy-6-(E-2-pyridyliminomethyl)-phenol (L1) are described. In comparison with the similar 2-(pyridine-2-ylimino-methyl)phenol (pymp), the mode of coordination of L1 is altered due to the presence of methoxy substituent introducing the sterical hindrance. During the synthesis of the complexes, partial hydrolysis of the ligand was observed. Since such immediate hydrolysis of L1 was not detected during the reactions of Zn(II) and Cu(II) salts with L1, the DFT calculated structures of a series of similar Zn, Cu, Ni, and Co complexes with L1 are compared to account for the phenomenon.

I complessi metallici con leganti carbenici N-eterociclici (NHC) sono una classe di composti che sono stati studiati negli ultimi anni per diverse applicazioni come materiali luminescenti, in chimica bioinorganica, come sensori, come polimeri organometallici e cristalli liquidi. Sono poi ampiamente utilizzati in catalisi omogenea, grazie alla loro particolare stabilità, dovuta alla elevata forza del legame metallo-NHC; un altro vantaggio è dovuto alla facilità con cui è possibile modificare le proprietà steriche ed elettroniche dei leganti carbenici N-eterociclici e di conseguenza anche quelle dei corrispondenti complessi metallici. I leganti NHC bidentati possono presentare una coordinazione chelante o a ponte e possono essere utilizzati per sintetizzare complessi eterobimetallici. Questa tesi di dottorato è divisa in due argomenti, che si differenziano per il tipo di leganti carbenici bidentati utilizzati: i) Complessi polinucleari di argento(I) e oro(I) con il legante bitz ii) Complessi con leganti eteroditopici nNHC/tzNHC i) Complessi polinucleari di argento(I) e oro(I) con il legante bitz Il prolegante bitz•2HI è il precursore di un NHC bidentato, dove i due eterocicli sono direttamente collegati tra loro senza distanziatore. La struttura di questo tipo di leganti potrebbe limitare la geometria dei complessi preparati. Con metalli del gruppo 11 in configurazione d10 si prevedeva la formazione di complessi dinucleari [M2(bitz)2]X2 che avrebbero potuto presentare interazioni metallofiliche, spesso correlate con l'emissione nella banda visibile dello spettro elettromagnetico. I complessi di Ag(I) sono stati sintetizzati e poi i complessi di Au(I) sono stati ottenuti per transmetallazione. Questi complessi hanno mostrato la presenza di una specie dinucleare e di una specie trinucleare in equilibrio. I cristalli singoli, caratterizzati tramite SCXRD, hanno permesso di chiarire la struttura dei due isomeri e hanno mostrato la presenza di interazioni metallofiliche. Gli equilibri sono stati studiati con 1H NMR a temperatura variabile, tecniche DOSY NMR ed ESI-MS. È stato anche effettuato uno studio computazionale preliminare sulla struttura degli isomeri. Infine, sono state studiate le proprietà di fotoluminescenza dei due isomeri del complesso bitz di oro(I). ii) Complessi con leganti eteroditopici nNHC/tzNHC Sono state studiate le proprietà di coordinazione dei leganti nNHC (carbeni N-eterociclici basati sull’imidazolo) funzionalizzati con un secondo anello N-eterociclico, ovvero un carbene basato sull’1,2,3-triazolo. Complessi di Au(I) omobimetallici sono stati ottenuti a partire da un precursore nNHC/tzNHC e i diversi isomeri sono stati caratterizzati, inoltre i complessi dinucleari di oro(I) neutri sono stati sintetizzati e testati come precatalizzatori in reazioni di idroamminazione di alchini. Utilizzando un precursore nNHC con un 1,2,3-triazolo come sostituente e applicando l'approccio di metilazione a stadi, è stato sintetizzato e caratterizzato un complesso eterobimetallico Au(I)/Ag(I), che però è risultato instabile. Con l'obiettivo di ottenere complessi eterobimetallici Pd(II)/Au(I) è stata sviluppata una via di sintesi che non prevedesse la formazione dei complessi di argento. In primo luogo le proprietà di coordinazione di un nNHC con un 1,2,3-triazolo come sostituente sono state investigate verso il Pd(II), gli intermedi e gli isomeri in soluzione sono stati caratterizzati. In particolare sono stati isolati complessi di formula generale trans-[PdI2(NHC)2]. La successiva metilazione dell'anello triazolico dà un precursore per un secondo legante carbenico (tzNHC), che in seguito a deprotonazione e coordinazione, può poi formare complessi eterometallici. In questo caso, utilizzando AuCl(SMe2), è stata studiata la formazione di complessi eterobimetallici Pd(II)/Au(I), ma si sono formate diverse specie, anche come conseguenza di reazioni di scambio di leganti carbenici tra i metalli. Questi risultati confermano ancora una volta come sia difficile ottenere complessi eterobimetallici con leganti carbenici, adottando una procedura generale. I complessi di Pd(II) ottenuti sono stati utilizzati in test preliminari in reazioni di tipo Sonogashira.

Thin film nanostructures may be defined as assemblies, arrays, or randomly distributed nanoparticles, nanowires, or nanotubes, which together form a layer of materials supported on a substrate surface. Because such nanostructures are supported on a substrate surface, their potential applications cover a wide area in optical, magnetic, electrochemical, electromagnetic, and optoelectronic devices. The focus of the present thesis is the development of methodologies to grow certain thin film nanostructures of some transition metal oxides (TMOs), including copper oxides and LixCoO2, through CVD, sol-gel, and electromagnetic radiation-mediated approaches. The work towards this objective can be divided into three parts: first, the design, synthesis, and systematic identification of novel metalorganic precursors of copper (monometallic) and Li and Co (bimetallic); second, the growth of nanostructured oxides thin films using these precursors; and third, the application of electromagnetic radiation to control or tailor the growth of as grown nanostructures. The underlying growth mechanisms substantiated by appropriate evidence have been put forward, wherever found relevant and intriguing. It may be added that the principal objective of the work reported here has been to explore the several ideas noted above and examine possibilities, rather than to study any specific one of them in significant detail. It is hoped earnestly that this has been accomplished to a reasonable extent. Chapter 1 reviews briefly the reports available in the literature on three specific methods of growing thin films nanostructures, namely chemical vapour deposition, sol-gel processing and light-induced approach. The objective of this chapter has been to provide the background of the work done in the thesis, and is substantiated with a number of illustrative examples. Some of the fundamental concepts involved, viz., plasmons and excitons, have been defined with illustration wherever found relevant in the context of the work. Chapter 2 describes the various techniques used for synthesis and characterisation of the metalorganic complexes as well as of the thin films. This chapters covers mostly experimental details, with brief descriptions of the working principles of the analytical procedures adopted, namely, infrared spectroscopy, mass spectroscopy, elemental analysis, and thermal analysis for characterisation of the metalorganic complexes. This is followed by a similarly brief account of techniques employed to characterize the thin films prepared in this work, viz., glancing incidence X-ray diffraction (GIXRD), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), electrostatic force microscopy (EFM), transmission electron microscopy (TEM), glancing incidence infra-red spectroscopy (GIIR) and, UV-visible spectroscopy. The metalorganic chemical vapour deposition (MOCVD) systems built in house and used for growth of films are described in detail. The topics in the different sections of the chapter are accompanied by pertinent diagrams. Chapter 3 deals with the design, synthesis and characterisation of novel polynuclear complexes of copper and cobalt. Keeping in mind the various advantages such as low toxicity, ease of synthesis, non-pyrophoricity, and low temperature volatility, of environmentally benign complexes based on biologically compatible such as triethanolamine, diethanolamine, the objective has been to synthesize complexes containing triethanolamine and diethanolamine of transition metals such as cobalt and copper, and to investigate their applicability in MOCVD processes as a novel class of precursors. With the notion of ‘better’ and efficient design of precursors, an attempt has been made, through a semi-empirical modeling, to understand the correlation between volatility and various intrinsic molecular parameters such as lattice energy, vibrational-rotational energy, and internal symmetry. Chapter 4 discusses the growth of nanoporous Cu4O3-C composite films through the MOCVD process employing Cu4(deaH)(dea)(oAc)5.(CH3)2CO as the precursor. The various characteristic aspects of as-grown films, such as their crystallinity, morphology, and composition have been covered elaborately in various sections of this chapter. The chapter describes the efficient guiding and confining of light exploiting the photonic band gap of these nanoporous films, which indicates the potential usefulness of these and similar films as optical waveguides. A model described in the literature on absorbing photonic crystals, wherein a periodically modulated absorption entails an inevitable spatial modulation of dispersion, i.e., of the index contrast to open a photonic band gap, has been used to calculate the indices of refraction of one of these nanoporous films. The chapter also reports briefly the preliminary electrochemical investigations carried out on a typical film, examining the notion of its application as the anode in a Li-ion rechargeable battery. Chapter 5 describes the synthesis of nanocrystalline LixCoO2 films by the sol-gel method. Reports available in literature indicate that the various phases of LixCoO2 are extremely sensitive to processing temperature, making it difficult to control dimensionality of a given phase using temperature as one of process parameters. We have investigated the possibility of using incoherent light to tailor the particle size/shape of this material. The as-grown and irradiated films were characterised by X-ray diffraction, and by microscopic and spectroscopic techniques.Optical spectroscopy was carried out in order to gain insight into the physico-chemical mechanism involved in such structural and morphological transformation. Chapter 6 deals with the synthesis of self-assembled nanostructures from the pre-synthesized nanocrystals building blocks, through optical means of exciton formation and dissociation. It has been demonstrated that, upon prolonged exposure to (incoherent) ultraviolet-visible radiation, LixCoO2 nanocrystals self-assemble into acicular architectures, through intermediate excitation of excitons. Furthermore, it has been shown that such self-assembly occurs in nanocrystals, which are initially anchored to the substrate surface such as that of fused quartz. This new type of process for the self-assembly of nanocrystals, which is driven by light has been investigated by available microscopic and spectroscopic techniques. Chapter 7 describes the stabilisation of chemically reactive metallic lithium in a carbonaceous nanostructure, viz., a carbon nanotube, achieved through the MOCVD process involving a lithium-alkyl moiety. This moiety is formed in situ during deposition through partial decomposition of a metalorganic precursor synthesized in house, which contains both lithium and cobalt. It is surmised that the stabilization of metallic Li in the nanostructure in situ occurs through the partial decomposition of the metalorganic precursor. Quantitative X-ray photoelectron spectroscopy carried out on such a film reveals that as much as 33.4% metallic lithium is trapped in carbon. Lastly, Chapter 8 briefly highlights the outlook for further investigations suggested by the work undertaken for this thesis. Novel precursors derived from biologically compatible ligands can open up possibility of growing new type of micro/nano-structures, and of unusual phases in the CVD grown films. Furthermore, it is proposed that the novel method of growth and alignment of nanocrystals through irradiation with incoherent light, employed for the specific material LixCoO2, may be employed for various other metallic and semiconducting materials.

Thin film nanostructures may be defined as assemblies, arrays, or randomly distributed nanoparticles, nanowires, or nanotubes, which together form a layer of materials supported on a substrate surface. Because such nanostructures are supported on a substrate surface, their potential applications cover a wide area in optical, magnetic, electrochemical, electromagnetic, and optoelectronic devices. The focus of the present thesis is the development of methodologies to grow certain thin film nanostructures of some transition metal oxides (TMOs), including copper oxides and LixCoO2, through CVD, sol-gel, and electromagnetic radiation-mediated approaches. The work towards this objective can be divided into three parts: first, the design, synthesis, and systematic identification of novel metalorganic precursors of copper (monometallic) and Li and Co (bimetallic); second, the growth of nanostructured oxides thin films using these precursors; and third, the application of electromagnetic radiation to control or tailor the growth of as grown nanostructures. The underlying growth mechanisms substantiated by appropriate evidence have been put forward, wherever found relevant and intriguing. It may be added that the principal objective of the work reported here has been to explore the several ideas noted above and examine possibilities, rather than to study any specific one of them in significant detail. It is hoped earnestly that this has been accomplished to a reasonable extent. Chapter 1 reviews briefly the reports available in the literature on three specific methods of growing thin films nanostructures, namely chemical vapour deposition, sol-gel processing and light-induced approach. The objective of this chapter has been to provide the background of the work done in the thesis, and is substantiated with a number of illustrative examples. Some of the fundamental concepts involved, viz., plasmons and excitons, have been defined with illustration wherever found relevant in the context of the work. Chapter 2 describes the various techniques used for synthesis and characterisation of the metalorganic complexes as well as of the thin films. This chapters covers mostly experimental details, with brief descriptions of the working principles of the analytical procedures adopted, namely, infrared spectroscopy, mass spectroscopy, elemental analysis, and thermal analysis for characterisation of the metalorganic complexes. This is followed by a similarly brief account of techniques employed to characterize the thin films prepared in this work, viz., glancing incidence X-ray diffraction (GIXRD), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), electrostatic force microscopy (EFM), transmission electron microscopy (TEM), glancing incidence infra-red spectroscopy (GIIR) and, UV-visible spectroscopy. The metalorganic chemical vapour deposition (MOCVD) systems built in house and used for growth of films are described in detail. The topics in the different sections of the chapter are accompanied by pertinent diagrams. Chapter 3 deals with the design, synthesis and characterisation of novel polynuclear complexes of copper and cobalt. Keeping in mind the various advantages such as low toxicity, ease of synthesis, non-pyrophoricity, and low temperature volatility, of environmentally benign complexes based on biologically compatible such as triethanolamine, diethanolamine, the objective has been to synthesize complexes containing triethanolamine and diethanolamine of transition metals such as cobalt and copper, and to investigate their applicability in MOCVD processes as a novel class of precursors. With the notion of ‘better’ and efficient design of precursors, an attempt has been made, through a semi-empirical modeling, to understand the correlation between volatility and various intrinsic molecular parameters such as lattice energy, vibrational-rotational energy, and internal symmetry. Chapter 4 discusses the growth of nanoporous Cu4O3-C composite films through the MOCVD process employing Cu4(deaH)(dea)(oAc)5.(CH3)2CO as the precursor. The various characteristic aspects of as-grown films, such as their crystallinity, morphology, and composition have been covered elaborately in various sections of this chapter. The chapter describes the efficient guiding and confining of light exploiting the photonic band gap of these nanoporous films, which indicates the potential usefulness of these and similar films as optical waveguides. A model described in the literature on absorbing photonic crystals, wherein a periodically modulated absorption entails an inevitable spatial modulation of dispersion, i.e., of the index contrast to open a photonic band gap, has been used to calculate the indices of refraction of one of these nanoporous films. The chapter also reports briefly the preliminary electrochemical investigations carried out on a typical film, examining the notion of its application as the anode in a Li-ion rechargeable battery. Chapter 5 describes the synthesis of nanocrystalline LixCoO2 films by the sol-gel method. Reports available in literature indicate that the various phases of LixCoO2 are extremely sensitive to processing temperature, making it difficult to control dimensionality of a given phase using temperature as one of process parameters. We have investigated the possibility of using incoherent light to tailor the particle size/shape of this material. The as-grown and irradiated films were characterised by X-ray diffraction, and by microscopic and spectroscopic techniques.Optical spectroscopy was carried out in order to gain insight into the physico-chemical mechanism involved in such structural and morphological transformation. Chapter 6 deals with the synthesis of self-assembled nanostructures from the pre-synthesized nanocrystals building blocks, through optical means of exciton formation and dissociation. It has been demonstrated that, upon prolonged exposure to (incoherent) ultraviolet-visible radiation, LixCoO2 nanocrystals self-assemble into acicular architectures, through intermediate excitation of excitons. Furthermore, it has been shown that such self-assembly occurs in nanocrystals, which are initially anchored to the substrate surface such as that of fused quartz. This new type of process for the self-assembly of nanocrystals, which is driven by light has been investigated by available microscopic and spectroscopic techniques. Chapter 7 describes the stabilisation of chemically reactive metallic lithium in a carbonaceous nanostructure, viz., a carbon nanotube, achieved through the MOCVD process involving a lithium-alkyl moiety. This moiety is formed in situ during deposition through partial decomposition of a metalorganic precursor synthesized in house, which contains both lithium and cobalt. It is surmised that the stabilization of metallic Li in the nanostructure in situ occurs through the partial decomposition of the metalorganic precursor. Quantitative X-ray photoelectron spectroscopy carried out on such a film reveals that as much as 33.4% metallic lithium is trapped in carbon. Lastly, Chapter 8 briefly highlights the outlook for further investigations suggested by the work undertaken for this thesis. Novel precursors derived from biologically compatible ligands can open up possibility of growing new type of micro/nano-structures, and of unusual phases in the CVD grown films. Furthermore, it is proposed that the novel method of growth and alignment of nanocrystals through irradiation with incoherent light, employed for the specific material LixCoO2, may be employed for various other metallic and semiconducting materials.

A new hyphenated instrument for the detection of fluorescent polynuclear aromatic hydrocarbons in complex enviromental samples is described. The instrument combines a high resolution separation tool, capillary gas chromatography, with a high resolution spectroscopic instrument, laser fluorescence excitation spectroscopy. Optimal interfacing of these two devices is accomplished by means of a novel pulsed free jet expansion system which withstands temperatures to 300°C, has a very low dead volume, pro vides an excellent duty factor match between the steady-state gas chromatograph and the pulsed laser, and yields cooled, isolated gas phase molecules for high resolution spectroscopy. As a test of the system, a complex environmental sample was analyzed for the geometric isomers of monomethylanthracene.