Structural studies of dithiocarbamate metal complexes and dicarboxylic acid metal salts

Abstract

This thesis composed of two chapters of work applying the elements of coordination chemistry, supramolecular chemistry and crystal engineering. A total of eleven (11) metal complexes were successfully synthesised and the crystals of each complex were characterised using Single Crystal X-ray Diffraction (SCXRD) analysis. Crystallographic study is the main focus of this research principally to highlight the molecular interactions that govern the crystal formation. The first part of the chapters described a series of transition metal ions; Fe(III), Co(III), Ni(II), Cu(II), Zn(II) and Cd(II), each coordinated with sodium morpholine-4-carbodithioate ligand, Na[S2CNC4H8O]. This series displayed versatile coordination modes; mononuclear complexes for Fe(III), Co(III), Ni(II) and Cu(II), bimetallic complex for Zn(II) and polymeric complex for Cd(II). This chapter outlined the structural aspect of dithiocarbamate complexes and its binding behaviour towards transition metal groups. All complexes were characterised using SCXRD and spectroscopic techniques including FT-IR and PXRD. CHN elemental analysis was done to analyse elemental composition of each complex. TGA was performed to study the thermal stability of each complex. The second part of the chapters described a metal salt series of 2,6-pyridinedicarboxylic acid (H2dipic). In this series, anionic metal complexes were prepared and stabilised by organic cations to form five (5) metal salts complexes. The complexes were synthesised using H2dipic as the coordinating ligand (anion) and amine as the counter ion (cation) with Ni(II), Cu(II) and Cd(II) metal ions to give complexes of [Ni(dipic)2][enH2], [Cd(dipic)3][enH2]2, [Cu(dipic)2][1mpH2], [Ni(dipic)2][1epH2] and [Cd2(dipic)4(opdH)2][opdH]2 respectively. These complexes are charge-dependent compounds, which were stabilised by protonated amines, viz., ethylenediamine (enH2), 1-methylpiperazine (1mpH2), 1-ethylpiperazine (1epH2) and o-phenylenediamine (opH). This series focuses on the self-assembly of the molecules and the non-covalent interactions present in the crystal structures, which combined the principle of crystal engineering and supramolecular chemistry. Henceforth, the self-assembly and molecular recognition process between the ligand, amine and metal ion (and also solvent) will lead to the deprotonation of the ligand and subsequent protonation of the organic counter ions in order to achieve stability in the crystal structure formation. Crystal structures of all the metal salt complexes were determined using SCXRD. Additional analysis for structural comparison between the bulk materials and crystal data from SCXRD was done via PXRD.