Synthesis, crystal structure, BSA binding and antibacterial studies of Ni(II) complexes derived from dithiocarbazate based ligands

Abstract

A series of nickel(II) bis-complexes of the type [NiL2] C1-C4, where L is a tridentate (NNS) ligand have been isolated and characterized by conductivity studies, elemental analyses, IR and UV–Vis spectral measurements. The single crystal X-ray diffraction studies on [Ni(L1)2] C1 and [Ni(L3)2] C3 reveal that the deprotonated tridentate (NNS) ligands are meridionally coordinated to ascertain a distorted octahedral coordination geometry around nickel(II). The [Ni(L1)2] complex crystallizes in the monoclinic space group P21/c with a = 9.5009(4) Å, b = 13.3354(4) Å, c = 16.7988(7) Å, α = 90 °, β = 98.946(4)°, γ = 90° and Z = 4 while [Ni(L3)2] crystallizes in the monoclinic space group P21/c with a = 16.1362(19), b = 20.2502(11), c = 8.5462(5), α = 90 °, β = 102.778(8)°, γ = 90 ° and Z = 4. The antibacterial potencies of the compounds C1-C4 were estimated on the growth of P. aeruginosa, a Gram-negative bacterium, and S. mutans, a Gram-positive bacterium by broth culture and biofilm formation assay. The interaction between bovine serum albumin (BSA) was investigated using fluorescence quenching techniques. The results revealed that the fluorescence quenching of BSA is through a static quenching process. The binding constants and the number of binding sites were determined using fluorescence quenching data. The binding distance between BSA and Ni-complexes has been determined by using the fluorescence resonance energy transfer method.