Investigation of structurally diversified homo and heterometallic complexex

Abstract

The objectives of this thesis were to develop N-containing pyridine ligand based homometallic and heterometallic metal complexes and their high dimensional networks via coordinate bond and non-covalent secondary interactions. These complexes have been mainly synthesized either by insitu metal ligand reaction or by alteration of reaction medium by using Cd and Hg as well as noble metal (Au) at ambient conditions. This thesis has been divided into six chapters. The chapter 1 is introductory chapter which includes the brief introduction of pyridine based ligands and their metal complexes then it moves towards the hydrothermal or solvothermal one pot in-situ metal ligand reactions technique as well as effect of reaction medium on structural variation of metal complexes. Further discussion has been extended with the isolation and structural characterization of metastable intermediate. This chapter also includes the the role of noble metal such as Au in the formation of supramolecular network via its own relativistic effect as Au∙∙∙Au or Au∙∙∙H−C interactions and their luminescent properties. Chapter 2 deals with synthesis and characterization of Hg(II) based C−C coupled 1D polymeric chain at ambient conditions with 1:1 ratio via in-situ metal/ligand reaction. However, a new class of μ-oxo and μ-chloro bridged other polymeric chain has been obtained by altering the metal : ligand ratio to 1 : 2) . Furthermore, three other 1D polymeric chains of Hg(II) and Cd(II) have been developed under the same reaction conditions. In Chapter 3, a double open cubane tetramer of Cd(II) has been synthesized by the reaction of CdCl2 with hep-H [hep-H = 2-(2-hydroxyethyl)pyridine] in MeOH at room temperature. This discrete tetramer on reaction with methanolic HCl, HNO3, and H2SO4 transformed into a two one-dimensional (1D) polymeric chain and one three-dimensional network with topology seh-4,6-C2/c net, respectively. Similar to tetramer, two other Cd based polymeric chains have been developed upon treatment of methanolic HCl, on 1D polymeric chains synthesized in chapter 1. Chapter 4 deals with the isolation as well as structural characterization of a kinetically controlled metastable heterometallic 1D polymeric intermediate along with the thermodynamically driven Cu(II)−Hg(II) 1D polymeric chain and a monomeric Cu(II) complex obtained during recrystallization in methanol. Chapter 5 includes the synthesis characterization and structural aspect of dimeric and trimeric complexes of Hg(II) and Cd(II) with the amide ligand, H2L (H2L = N,N’-bis[2-(2-pyridyl)methyl]pyridine-2,6- dicarboxamide). Molecular structures of both complexes were confirmed by single crystal X-ray studies. The varying coordination modes of H2L gave rise to different electrochemical behavior of dimer and trimer, which were also rationalized by theoretical calculations. Chapter 6 presents, synthesis and characterization of new anthracene derived dinuclear Au(I)-diacetylide complex in which two Au(I) units are attached at 9,10- positions of ethynyl anthracene moiety. This complex exhibited rare non-covalent intermolecular Au∙∙∙H−C interactions, leading to the formation of a supramolecular 2D-network. Further, to understand the effect of Au(I) units at different position, two other complexes were synthesized, where Au(I) units were attached to 2,6- and 1,8- positions of anthracene, respectively. The absorption and emission spectra of all the complexes have been studied and surprisingly complex having Au(I) at 9, 10 position was found to be highly fluorescent with high quantum yield compared to 2,6 and 1,8 positions this may be due to more perturbation of Au(I) on π system. Complexes have been characterized by elemental analysis, NMR and Mass spectroscopy and authenticated by their singlecrystal X-ray structures.