Divalent Nickel Complexes of Thiosemicarbazone Based on 5-Bromosalicylaldehyde and Triphenylphosphine: Experimental and Theoretical Characterization

Abstract

Two nickel(II) complexes containing 5-bromosalicylidene-N-methyl-S-methyl-isothiosemicarbazone (H<inf>2</inf>SMeNMeTsc) and 5-bromosalicylidene-N-methyl-thiosemicarbazone (H<inf>2</inf>NMeTsc) with triphenylphosphine were synthesized. The compounds were characterized by elemental analysis, IR, 1H NMR and UV-Vis spectroscopies, and their structures were determined by single crystal X-ray diffraction technique. Theoretical characterization of the compounds was carried out using the density functional theory (DFT/B3LYP) method with 6-311G(d,p) basis set for the C, H, Br, N, O, P, S atoms and LANL2DZ pseudo-potential for Ni atom, and the results were checked against the experimental data. Electronic absorption spectra of the compounds have also been obtained using the time-dependent density functional theory (TD-DFT) formalism at the same level. The coordination geometry around NiII in the two complexes is distorted square-planar geometry. While the thiosemicarbazone ligand is coordinated to nickel through ONN mode in [Ni(SMeNMeTsc)(PPh<inf>3</inf>)]·PPh<inf>3</inf>, it is bound to the metal as dianionic ONS donors in [Ni(NMeTsc)(PPh<inf>3</inf>)]. The consistency between theoretical and experimental values is good in general. © 2016 Elsevier Ltd. All rights reserved.