Hydrosilylation and hydroboration catalyzed by imido-hydride complexes of molybdenum (IV)

This thesis describes the synthesis, structural studies, stoichiometric and catalytic reactivity of novel Mo(IV) imido hydride complexes (Cp)(ArN)Mo(H)(PMe3) (1) and (Tp )(ArN)Mo(H)(PMe3) (2). Both 1 and 2 catalyze hydrosilylation of a variety of carbonyls. Detailed kinetic and DFT studies found that 1 reacts by an unexpected associative mechanism, which does not involve Si-H addition either to the imido group or the metal. Despite 1 being a d2 complex, its reaction with PhSiH3 proceeds via a a-bond metathesis mechanism giving the silyl derivative (Cp )(ArN)Mo(SiH2Ph)(PMe3). In the presence of BPh3 reaction of 1 with PhSiH3 results in formation of (Cp)(ArN)Mo(SiH2Ph)(H)2 and (Cp)(ArN)Mo(SiH2Ph)2(H), the first examples ofMo(VI) silyl hydrides. AI: 1 : 1 reaction between 2, PhSiD3 and carbonyl substrate established that hydrosilylation is not accompanied by deuterium incorporation into the hydride position of the catalyst, thus ruling out the conventional mechanism based on carbonyl insertion carbonyl. As 2 is nomeactive to both the silane and ketone, the only mechanistic alternative we are left with is that the metal center activates the carbonyl as a Lewis acid. The analogous nonhydride mechanism was observed for the catalysis by (ArN)Mo(H)(CI)(PMe3), (Ph3P)2(I)(O)Re(H)(OSiMe2Ph) and (PPh3CuH)6. Complex 2 also catalyzes hydroboration of carbonyls and nitriles. We report the first case of metal-catalyzed hydroboration of nitriles as well as hydroboration of carbonyls at very mild conditions. Conversion of carbonyl functions can be performed with high selectivities in the presence of nitrile groups. This thesis also reports the first case of the HlH exchange between H2 and Si-H of silanes mediated by Lewis acids such as Mo(IV) , Re(V) , Cu(I) , Zn(II) complexes, B(C6Fs)3 and BPh3.

Ligand Design for Dual Property Single Molecule Magnets

This thesis describes two different approaches for the preparation of polynuclear clusters with interesting structural, magnetic and optical properties. Firstly, exploiting p-tert-butylcalix[4]arene (TBC4) macrocycles together with selected Ln(III) ions for the assembly of emissive single molecule magnets, and secondly the preparation and coordination of a chiral mpmH ligand with selected 3d transition metal ions, working towards the discovery of chiral polynuclear clusters. In Project 1, the coordination chemistry of the TBC4 macrocycle together with Dy(III) and Tb(III) afforded two Ln6[TBC4]2 complexes that have been structurally, magnetically and optically characterized. X-ray diffraction studies reveal that both complexes contain an octahedral core of Ln6 ions capped by two fully deprotonated TBC4 macrocycles. Although the unit cells of the two complexes are very similar, the coordination geometries of their Ln(III) ions are subtly different. Variable temperature ac magnetic susceptibility studies reveal that both complexes display single molecule magnet (SMM) behaviour in zero dc field and the energy barriers and associated pre-exponential factors for each relaxation process have been determined. Low temperature solid state photoluminescence studies reveal that both complexes are emissive; however, the f-f transitions within the Dy6 complex were masked by broad emissions from the TBC4 ligand. In contrast, the Tb(III) complex displayed green emission with the spectrum comprising four sharp bands corresponding to 5D4 → 7FJ transitions (where J = 3, 4, 5 and 6), highlighting that energy transfer from the TBC4 macrocycle to the Tb(III) ion is more effective than to Dy. Examples of zero field Tb(III) SMMs are scarce in the chemical literature and the Tb6[TBC4]2 complex represents the first example of a Tb(III) dual property SMM assembled from a p-tert-butylcalix[4]arene macrocycle with two magnetically derived energy barriers, Ueff of 79 and 63 K. In Project 2, the coordination of both enantiomers of the chiral ligand, α-methyl-2-pyridinemethanol (mpmH) to Ni(II) and Co(II) afforded three polynuclear clusters that have been structurally and magnetically characterized. The first complex, a Ni4 cluster of stoichiometry [Ni4(O2CCMe3)4(mpm)4]·H2O crystallizes in a distorted cubane topology that is well known in Ni(II) cluster chemistry. The final two Co(II) complexes crystallize as a linear mixed valence trimer with stoichiometry [Co3(mpm)6]·(ClO4)2, and a Co4 mixed valence complex [Co(II)¬2Co(III)2(NO3)2(μ-mpm)4(ONO2)2], whose structural topology resembles that of a defective double cubane. All three complexes crystallize in chiral space groups and circular dichroism experiments further confirm that the chirality of the ligand has been transferred to the respective coordination complex. Magnetic susceptibility studies reveal that for all three complexes, there are competing ferro- and antiferromagnetic exchange interactions. The [Co(II)¬2Co(III)2(NO3)2(μ-mpm)4(ONO2)2] complex represents the first example of a chiral mixed valence Co4 cluster with a defective double cubane topology.

Melanosomal targeting sequences from gp100 are essential for MHC class II-restricted endogenous epitope presentation and mobilization to endosomal compartments

CD4+ T lymphocytes play an important role in CD8+ T cell-mediated responses against tumors. Considering that about 20% of melanomas express major histocompatibility complex (MHC) class II, it is plausible that concomitant antigenic presentation by MHC class I and class II complexes shapes positive (helper T cells) or negative (regulatory T cells) anti-tumor responses. Interestingly, gp100, a melanoma antigen, can be presented by both MHC class I and class II when expressed endogenously, suggesting that it can reach endosomal/MHC class II compartments (MIIC). Here, we demonstrated that the gp100 putative amino-terminal signal sequence and the last 70 residues in carboxy-terminus, are essential for MIIC localization and MHC class II presentation. Confocal microscopy analyses confirmed that gp100 was localized in LAMP-1+ endosomal/MIIC. Gp100-targeting sequences were characterized by deleting different sections in the carboxy-terminus (residues 590 to 661). Transfection in 293T cells, expressing MHC class I and class II molecules, revealed that specific deletions in carboxy-terminus resulted in decreased MHC class II presentation, without effects on MHC class I presentation, suggesting a role in MIIC trafficking for these deleted sections. Then, we used these gp100-targeting sequences to mobilize the green fluorescent protein (GFP) to endosomal compartments, and to allow MHC class II and class I presentation of minimal endogenous epitopes. Thus, we concluded that these specific sequences are MIIC targeting motifs. Consequently, these sequences could be included in expression cassettes for endogenously expressed tumor or viral antigens to promote MHC class II and class I presentation and optimize in vivo T cell responses, or as an in vitro tool for characterization of new MHC class II epitopes.

Études spectroscopiques expérimentales et théoriques de complexes de métaux de transition

Cette thèse présente une série d'études qui visent la compréhension de la structure électronique de complexes de métaux de transition en employant diverses méthodes de spectroscopie. L'information sur la structure électronique aide à comprendre et développer des nouveaux matériaux, des nouvelles voies de synthèses, ainsi que des nouveaux modèles théoriques. Habituellement, afin d'explorer la structure électronique d'un système qui comporte en son centre un métal de transition, l'information fournie par les spectres d'un seul composé n'est pas suffisante. On étudie une série de composés similaires, qui ont le même métal de transition à un degré d'oxydation donné, ainsi que des ligands qui forment des liaisons de différentes forces et caractéristiques avec le métal. Cependant, ces changements, bien qu'on les désire de faible impact, créent une grande perturbation de la structure électronique visée par les études. Afin d'étudier en profondeur une seule structure électronique, nous employons une stratégie d'analyse moins perturbante. Nous appliquons une pression hydrostatique sur les complexes de métaux de transition. Cette pression perturbe le système suffisamment pour nous livrer davantage d'informations sur la structure électronique, sans la « dénaturer ». Afin d'étudier précisément ces systèmes perturbés, la technique d'application de pression est conjuguée, dans la littérature, aux diverses techniques de spectroscopie d'absorption UV-visible, de luminescence, ainsi que de diffusion Raman. Pour extraire un maximum d'informations de ces expériences, on emploie des techniques de calculs de structure électronique ainsi que de dynamique des noyaux. Dans cette thèse, on tente de mettre en lumière la structure électronique de composés de molybdène(IV), de platine(II) et palladium(II) à l'aide de la technique de pression couplée aux spectroscopies de luminescence et de diffusion Raman. Dans le chapitre 3, on observe un déplacement de la bande de luminescence de +12 cm-1/kbar entre la pression ambiante et 25 kbar pour le complexe trans-[MoOCl(CN-t-Bu)4]BPh4, dont le centre métallique molybdène(IV)est de configuration électronique 4d2. Il s'agit de la première variation positive observée pour un complexe de type métal-oxo. À des pressions plus élevées, la tendance s'inverse. Le maximum d'énergie de la bande de luminescence se déplace de -8 cm-1/kbar. Ce changement de variation présage d'une compétition interne entre les ligands situés sur les différents axes de l'octaèdre. À l'aide de calculs basés sur la théorie de la fonctionnelle de la densité, on propose un mécanisme pour expliquer ce phénomène. Au cours du chapitre 4, on étudie des complexes de palladium(II) et de platine(II) qui ont les mêmes ligands. Un de ces ligands est le 1,4,7-trithiacyclononane (ttcn). On constate qu'à basse pression le ligand est bidentate. Par contre, lorsque la pression augmente, on constate, par exemple à l'aide du complexe [Pt(ttcn)Cl2], qu'une interaction anti-liante supplémentaire se produit entre le ligand ttcn et le métal, ce qui change la nature de l'orbitale HOMO. On observe un déplacement de la bande de luminescence de -19 cm-1/kbar. Tel que pour le complexe de molybdène(IV), le déplacement de la bande de luminescence dépend de la compétition entre les ligands situés sur les différents axes de l'octaèdre. L'interaction liante entre l'ion platine(II) et l'atome de soufre axial est l'effet le plus plausible qui peut induire un déplacement de la bande de luminescence vers les basses énergies. Ceci nous indique que cette interaction domine. Par contre, pour ce qui est du complexe palladium(II), la compétition est remportée par d'autres effets, car le déplacement de la bande de luminescence est de +6 cm-1/kbar. Encore une fois, des calculs, basés sur la théorie de la fonctionnelle de la densité, aident à explorer les causes de ces observations en suggérant des explications corroborées simultanément par les diverses expériences de spectroscopie. Lors du chapitre 5, une étude plus exacte de la structure électronique ainsi que de la dynamique des noyaux de complexes de métaux de transition est présentée. En effet, les complexes de palladium(II) et de platine(II), de type [M(X)4]2-, ont une structure simple, très symétrique. Le premier état excité de ces molécules subit la distorsion Jahn-Teller. On veut établir un protocole de travail pour les expérimentateurs afin d'analyser des spectres de molécules pour lesquelles l'approximation de Born-Oppenheimer n'est pas valide. On utilise la théorie de la fonctionnelle de la densité dépendante du temps ainsi que le modèle de Heidelberg afin de décrire des effets non adiabatique. On tente d'établir l'influence des effets non adiabatiques sur les spectres de ce type de complexe.

Synthesis and properties of d6 metal complexes of bidentate and tridentate ‘super donor’ ligands

La polyvalence de la réaction de couplage-croisé C-N a été explorée pour la synthèse de deux nouvelles classes de ligands: (i) des ligands bidentates neutres de type N^N et (ii) des ligands tridentates neutres de type N^N^N. Ces classes de ligands contiennent des N-hétérocycles aromatiques saturés qui sont couplés avec hexahydropyrimidopyrimidine (hpp). Les ligands forment de cycles à six chaînons sur la coordination du centre Ru(II). Ce fait est avantageux pour améliorer les propriétés photophysiques des complexes de polypyridyl de Ru(II). Les complexes de Ru(II) avec des ligands bidentés ont des émissions qui dépendent de la basicité relative des N-hétérocycles. Bien que ces complexes sont électrochimiquement et photophysiquement attrayant, le problème de la stereopurité ne peut être évité. Une conception soigneuse du type de ligand nous permet de synthétiser un ligand bis-bidentate qui est utile pour surmonter le problème de stereopurité. En raison de la spécialité du ligand bis-bidentate, son complexe diruthénium(II,II) présente une grande diastéréosélectivité sans séparation chirale. Alors que l'unité de hpp agit comme un nucléophile dans le mécanisme de C-N réaction de couplage croisé, il peut également agir en tant que groupe partant, lorsqu'il est activé avec un complexe de monoruthenium. Les complexes achiraux de Ru(II) avec les ligands tridentés présentent des meilleures propriétés photophysiques en comparason avec les prototypes [Ru(tpy)2]2+ (tpy = 2,2′: 6′, 2′′-terpyridine). L’introduction de deux unités de hpp dans les ligands tridentates rend le complexe de Ru(II) en tant que ‘absorbeur noir’ et comme ‘NIR émetteur’ (NIR = de l’anglais, Near Infra-Red). Cet effet est une conséquence d'une meilleure géométrie de coordination octaédrique autour de l'ion Ru(II) et de la forte donation sigma des unités hpp. Les complexes du Re(I) avec des ligands tridentates présentent un comportement redox intéressant et ils émettent dans le bleu. L'oxydation quasi-réversible du métal est contrôlée par la donation sigma des fragments hpp, tandis que la réduction du ligand est régie par la nature électronique du motif N-hétérocycle central du ligand lui-même. Cette thèse presente également l'auto-assemblage des métal-chromophores comme ‘métallo-ligands’ pour former des espèces supramoléculaires discretes utilisant des complexes neutres. Les synthèses et propriétés des métaux-chromophores précités et les supramolécules sont discutées.

Lactide polymerization with iron alkoxide complexes

Les essais préliminaires pour préparer des alcoolates de fer à partir du bichlorure ou bibromure de fer (II), en les combinant avec des ligands de type diimino pyridine, ont engendré la formation de complexes homoleptiques et hétéroleptiques, dépendant des substituants sur les branches imines du ligand. Ces complexes homoleptiques octaédriques et paramagnétiques ont été étudiés par rapport à leurs propriétés spectroscopiques et cristallographiques. De plus, la synthèse des complexes de fer hétéroleptique a engendré de bons précurseurs penta-coordonnés pour les réactions de substitution de ligands avec des alcoolates de métaux alcalins, de manière à produire les dialcoolates de fer (II) désirés. Des techniques d’analyse telles que la spectroscopie UV-vis, l’analyse élémentaire, la spectrométrie de masse à haute résolution et la cristallographie aux rayons X ont été utilisées pour caractériser ces complexes de fer. L’activité catalytique de ces complexes de fer (II) a aussi été étudiée par rapport à la polymérisation du lactide; les dialcoolates convoités ont été générés in-situ en raison de la difficulté à produire et à isoler les dérivés alcoolates des complexes diimino pyridine de fer. Une étude approfondie a aussi été faite sur les réactions de polymérisation, surtout par rapport aux valeurs de conversion à l’échelle du temps, ainsi qu’à la tacticité des chaines de polymères obtenues. Ces analyses ont été effectuées par l’entremise de la spectroscopie de résonance magnétique nucléaire, de la chromatographie d’exclusion stérique, et de la spectrométrie de masse MALDI (désorption-ionisation laser assistée par matrice).

Synthesis and Characterization Of Some Transition Metal Complexes Of Multidentate Ligands

Coordination chemistry of schiff bases is of considerable interest due to their various magnetic, catalytic and biological applications. Here it describes the spectral characterization of schiff bases and its Mn (II), Cu (II) and Ni (II) complexes. Then synthesis and spectral characterization of Zn (II), Cd (II) and Co (II) complexes of schiff base derived from 3-Formylsalicilic Acid and 1,3-diaminopropane. Then it discusses the synthesis and spectral studies of Copper (II) complexes of 2-Hydroxyacetophenone N-phenyl semicarbazone. Finally it discusses the synthesis and spectral characterization of Co (III) complexes of salicylaldehyde N-phenyl semicarbazone. The preparation and characterization of Cobalt (III) complexes of salicylaldehyde, N-phenylthiosemicarbazone containing hetrocyclic bases phenalthroline and bipyridine. Thiocyanate, azide and perchlorate ions act as coligands. Elemental analysis suggests +3 state for Cobalt. HNMR, IR and UV-visible spectra characterize the complexes.

Studies on Some New Metal-Hydrazone Complexes and Their Zeolite Encapsulated Analogues

The thesis deals with the synthesis, characterization and catalytic activity studies of some new Fe (III), Co (II), Ni (II) and Cu (II) complexes of hydrazones and their zeolite encapsulated analogues. Hydrazones have diverse applications in biological, non-biological and biochemical front. During the present study three hydrazone types of ligands namely, acetylacetone- 2-hydroxyphenylhydrazone (APAcAc), acetoacetanilide- 2-hydroxyphenylhydrazone (APAcAcA) and acetoacetanilide-3,5-dihydro-2,4-dione pyrimidylhydrazone (AUAcAcA) were synthesized by diazotization of primary amine and coupling with compounds containing active methylene group. First part of the thesis deals with the synthesis of Fe, Co, Ni and Cu complexes using three hydrazone types of ligands are given. Details regarding the characterization of these complexes with a view to establishing the molecular structures are presented in this part. The other part contains the method of encapsulation of these complexes in zeolite cavities and their characterizations of the encapsulated metal species are described. A comparitive account of the catalytic activities of the pure and encapsulated complexes for cyclohexanol oxidation was also carried out.

Studies on Some Simple and Zeolite-Y Encapsulated 3d-Transition Metal Complexes of Schiff Bases Derived From 2-Aminobenzothiazole

In this regard Schiff base complexes have attracted wide attention. Furthermore, such complexes are found to play important role in analytical chemistry, organic synthesis, metallurgy, refining of metals, electroplating and photography. Many Schiff base complexes are reported in literature. Their properties depend on the nature of the metal ion as well as on the nature of the ligand. By altering the ligands it is possible to obtain desired electronic environment around the metal ion. Thus there is a continuing interest in the synthesis of simple and zeolite encapsulated Schiff base complexes of metal ions. Zeolites have a number of striking structural similarities to the protein portion of natural enzymes. Zeolite based catalysts are known for their remarkable ability of mimicking the chemistry of biological systems. In view of the importance of catalysts in all the areas of modern chemical industries, an effort has been made to synthesize some simple Schiff base complexes, heterogenize them by encapsulating within the supercages of zeoliteY cavities and to study their applications. The thesis deals with studies on the synthesis and characterization of some simple and zeoliteY encapsulated Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) complexes and on the catalytic activity of these complexes on some oxidation reactions. Simple complexes were prepared from the Schiff base ligands SBT derived from 2-aminobenzothiazole and salicylaldehyde and the ligand VBT derived from 2-aminobenzothiazole and vanillin (4-hydroxy-3- methoxybenzaldehyde). ZeoliteY encapsulated Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) complexes of Schiff base ligands SBT and VBT and also of 2-aminobenzothiazole were synthesized. All the prepared complexes were characterized using the physico-chemical techniques such as chemical analysis (employing AAS and CHN analyses), magnetic moment studies, conductance measurements and electronic and FTIR spectra. EPR spectra of the Cu(II) complexes were also carried out to know the probable structures and nature of Cu(II) complexes. Thermogravimetric analyses were carried out to obtain the information regarding the thermal stability of various complexes. The successful encapsulations of the complexes within the cavities of zeoliteY were ascertained by XRD, surface area and pore volume analysis. Assignments of geometries of simple and zeoliteY encapsulated complexes are given in all the cases. Both simple and zeoliteY encapsulated complexes were screened for catalytic activity towards oxidation reactions such as decomposition of hydrogen peroxide, oxidation of benzaldehyde, benzyl alcohol, 1-propanol, 2-propanol and cyclohexanol.

Synthesis and Characterisation of New Transition Metal Complexes of Schiff Bases Derived from 3-hydroxyquinoxaline-2- carboxaldehyde and Application of Some ofthese Complexes as Hydrogenation and Oxidation Catalysts

The thesis deals with studies on the synthesis, characterisation and catalytic applications of some new transition metal complexes of the Schiff bases derived from 3-hydroxyquinoxaline 2-carboxaldehyde.. Schiff bases which are considered as ‘privileged ligands’ have the ability to stabilize different metals in different oxidation states and thus regulate the performance of metals in a large variety of catalytic transformations. The catalytic activity of the Schiff base complexes is highly dependant on the environment about the metal center and their conformational flexibility. Therefore it is to be expected that the introduction of bulky substituents near the coordination sites might lead to low symmetry complexes with enhanced catalytic properties. With this view new transition metal complexes of Schiff bases derived from 3-hydroxyquinoxaline-2-carboxaldehyde have been synthesised. These Schiff bases have more basic donor nitrogen atoms and the presence of the quinoxaline ring may be presumed to build a favourable topography and electronic environment in the immediate coordination sphere of the metal. The aldehyde was condensed with amines 1,8-diaminonaphthalene, 2,3-diaminomaleonitrile, 1,2-diaminocyclohexane, 2-aminophenol and 4-aminoantipyrine to give the respective Schiff bases. The oxovanadium(IV), copper(II) and ruthenium(II)complexes of these Schiff bases were synthesised and characterised. All the oxovanadium(IV) complexes have binuclear structure with a square pyramidal geometry. Ruthenium and copper form mononuclear complexes with the Schiff base derived from 4- aminoantipyrine while binuclear square planar complexes are formed with the other Schiff bases. The catalytic activity of the copper complexes was evaluated in the hydroxylation of phenol with hydrogen peroxide as oxidant. Catechol and hydroquinone are the major products. Catalytic properties of the oxovanadium(IV) complexes were evaluated in the oxidation of cyclohexene with hydrogen peroxide as the oxidant. Here allylic oxidation products rather than epoxides are formed as the major products. The ruthenium(II) complexes are found to be effective catalysts for the hydrogenation of benzene and toluene. The kinetics of hydrogenation was studied and a suitable mechanism has been proposed.

Studies on metal complexes with acylhydrazones based on heterocyclic carbonyl compounds

Dept.of Applied Chemistry, Cochin University of Science and Technology

Structural and biological investigations of metal complexes of some substituted thiosemicarbazones

Department of Applied Chemistry, Cochin University of Science and Technology

Spectral studies and crystal structures of some transition metal complexes of N4-substituted semicarbazones

The present work is concentrated on the studies of two novel semicarbazones, di-2-pyridyl ketone-N4-phenyl-3-semicarbazone (HL1) and quinoline-2-carboxaldehyde-N4-phenyl-3-semicarbazone (HL2). The compositions of these semicarbazones were determined by the CHN analyses. For the characterization of these compounds we have used IR, UV and NMR spectral studies. The molecular structure of quinoline-2-carboxaldehyde-N4-phenyl-3- semicarbazone (HL2) was obtained by single crystal X-ray diffraction studies. Also, we have synthesized Zn(II), Cd(II), Cu(II), Ni(II), Co(II) and Mn(II) complexes of these semicarbazones, HL1 and HL2. These complexes were characterized by various spectroscopic techniques, magnetic and conductivity studies. We could isolate single crystals of some Zn(II) and Cd(II) compounds suitable for X-ray diffraction studies. For other complexes we could not isolate single crystals of good quality for single crystal X-ray diffraction studies.

Chelating behavior of acylhydrazones towards transition metals:Spectral and structural aspects

The current work deals with the synthesis and characterization of metal complexes derived from some substituted acylhydrazones. The hydrazones under investigation were characterized by IR, UV, NMR spectral studies and the molecular structure of one of the hydrazones was solved by single crystal XRD studies. In the present work dioxovanadium(V), manganese(II), cobalt(II/III), nickel(II), copper(II), zinc(II) and cadmium(II) complexes were synthesized and characterized by various spectroscopic techniques, molar conductance measurements, magnetic susceptibility measurements and cyclic voltammetry. Single crystals of some of the complexes were isolated and characterized by single crystal X-ray diffraction.The thesis is divided into eight chapters. Chapter 1 gives an introduction on hydrazones, diversity in their chelating behavior and their application in various fields. This chapter also describes different analytical techniques employed for the characterization of hydrazones and their metal complexes. Chapter 2 includes the synthesis and characterization of two substituted acylhydrazones. This chapter also discusses how the coordination behavior of hydrazones under investigation is interesting. Chapters 3-8 discuss the synthesis and characterization of some transition metal complexes derived from the acylhydrazones under study.The hydrazones synthesized were found to exist in the amido form. Various characterization techniques were carried out to explore the structure of the synthesized complexes. The results indicate that both the hydrazones coordinate through the pyridyl and azomethine nitrogens and amide oxygen either in enolate or neutral form. Out of synthesized complexes V(V), Zn/Cd(II) and one of the cobalt complex was found to diamagnetic. We could isolate single crystals of some of the complexes and most of the complexes crystallized were found to have a distorted octahedral geometry. Thus X-ray crystallographic study which was used as major tool in the structure determination revealed that the hydrazones undergo a rotation about the azomethine bond on complexation. We hope the work presented in the thesis would be helpful for those who are working in the field of metal complexes and can further they can be utilized for various applications.