Synthesis and spectral studies of Ni(Ⅱ) complexes involving functionalized dithiocarbamates and triphenylphosphine: X-ray crystal structure, thermal stability, Hirshfeld surface analysis, DFT and biological evaluation

Abstract

New homoleptic [Ni(cpebdtc)2] (1), [Ni(cptpdtc)2] (2) and heteroleptic [Ni(cpebdtc)(NCS)(PPh3] (3), and [Ni(cptpdtc)(NCS)(PPh3] (4) complexes were synthesized and fully characterized by CHNS analysis, FT-IR, electronic, 1H, 13C NMR spectroscopy. In heteroleptic complexes (3, 4), the values of thiocyanide (ѵC-N) have been moved towards longer wavenumbers and the carbon signals of NCS2 have been moved to downfield in comparison to the homoleptic complexes (1, 2), thus suggests increased strength of thioureide bond because of π-accepting phosphine. Structure of complex 3 was obtained by single crystal X-ray diffraction technique that showed NiS2PN square planar distorted geometry around nickel atom. In complex 3, supramolecular frameworks are stabilized by π…π non-covalent interactions. The HOMO/LUMO energy values displayed satisfying interchange of a charge that takes place within a molecule. Molecular electrostatic potential (MEP) surface analysis has been performed to reveal charge distribution in the complex. Natural bond orbital (NBO) assessment has been done to demonstrate the donor–acceptor interconnections. The calculation of Fukui function was performed by population evaluation. The quantification of intermolecular interactions was obtained by Hirshfeld surface analysis. TG analyses of complexes (1 and 2) showed single step decomposition with the formation of binary NiS material. All the complexes showed significant scavenging activity. The in vitro antifungal potential of complexes (1–4) against three Candida strains (C. albicans, C. glabrata and C. tropicalis) by taking Fluconazole (FLC) as a reference drug, showed that 3 exhibit significant activity with MIC around 500 µg/ml against all strains. The hypochromism effect suggested that complexes 2 and 4 interacted with the Ct-DNA through an intercalative binding mode, which was further validated by molecular docking studies.