Mixed ligand complexes of cadmium(II) and copper(II) dithiocarbazate: Synthesis, spectral characterization, X-ray crystal structure

Abstract

Three dithiocarbazate complexes, CdL2 (1), Cu2L2(OAc)2 (2) and [CuLCl]n (3), are synthesized using S-allyl-3-[(2-pyridyl-methylene)]dithiocarbazate (HL) as tridentate ligand. All compounds are characterized by elemental analysis, molar conductance, FT-IR and UV–Vis spectroscopy, mass spectrometry and single crystal X-ray diffraction. In all the complexes, the ligand (L−) coordinates to the metal centers through the pyridine nitrogen, the azomethine nitrogen and the thiolate sulfur atoms. In compound 1, two ligand units encompass the cadmium(II) ion in bischelate distorted octahedral fashion. In the copper binuclear compound (2), each metal atom is coordinated to one L− ligand unit and the two copper atoms are held by two bridging acetate ligands. In the coordination polymer 3, copper has a distorted square pyramidal geometry in which L− holds three coordination positions and two chloride ligands complete the five-coordinated arrangement, so that each chlorine atom links two adjacent Cu centers. Molecular geometries, vibrational frequencies and optimized structure energies are compared using the density functional method (B3LYP) with 6–311++G(d,p) basis set. Electronic absorption spectra of compounds are predicted with TD-DFT studies and compared with experimental ones. Natural bond orbital analysis (NBO) is performed for HOMO-LUMO, charge delocalization, intramolecular hydrogen bonding and orbital contributions.