Characterization studies and cyclic voltammetry on nickel(II) amino acid dithiocarbamates with triphenylphosphine in the coordination sphere

Nickel(II) amino acid dithiocarbamate complexes of the composition [Ni(AAdtc)(PPh3)(NCS)], [Ni(AAdtc)(PPh3)(CN)] and [Ni(AAdtc)(PPh3)2]ClO4 [(AAdtc = dithiocarbamate derivatives of amino acids, i.e., glycine (glydtc), L-iso-leucine (i-leudtc) and L-proline (prodtc)] were synthesized. The compounds were characterized by IR and electronic spectroscopy, thermal analysis, cyclic voltammetry and conductivity measurements. In the case of the mixed ligand complexes, the thioureide n(C−N) values were shifted to higher wave numbers compared to [Ni(AAdtc)2]. This observation shows the increased strength of the thioureide bond due to the presence of the p-accepting phosphine. Electronic spectral studies suggest square planar geometry for the complexes. Thermal analyses of the complexes are in keeping with the proposed formulae. Almost all the complexes showed signs of decay above 170 °C. At around 390 °C, the final mass corresponded to NiS. Cyclic voltammetry showed a decrease of the electron density on the nickel in the mixed ligand complexes compared to [Ni(AAdtc)2]