3,4–Dimethyl diphenyldithiophosphate of mononuclear cobalt(II) with N-donor ligands: Synthesis, structural characterization, DFT and antibacterial studies

3,4–Dimethyl diphenyldithiophosphate of cobalt(II) with N-donor ligands [{(ArO)₂PS₂}₂CoL₂] [Ar = 3,4–(CH₃)₂C₆H₃ (1–3); L = C₅H₅N (1), 3,4–(CH₃)₂C₅H₃N (2) and 4–(C₂H₅)C₅H₄N (3)] have been synthesized and characterized by elemental analyses, infrared spectroscopy (IR), powder X-ray diffraction (PXRD) and single crystal X–ray analysis. Complex 1 crystallizes in the monoclinic space group P2₁/n whereas complexes 2 and 3 crystallize in the triclinic space group P¯1. The crystal structures of complexes 1–3 reveal mononuclear units with the Co(II) center chelated in bidentate fashion by four S atoms of the two diphenyldithiophosphate ligands. The N atoms from two donor ligands are axially coordinated, leading to distorted octahedral geometry around Co(II). The complexes have been optimized using density functional theory (DFT), structural parameters have been calculated, and the energy gaps of the frontier orbitals (HOMO–LUMO) have been predicted. Mayer bond orders have also been calculated. Structural parameters from the crystallographic and DFT studies are in good agreement with each other. To explore the biological potential, complexes were evaluated for their antibacterial activity against three bacterial strains. The bacterial growth inhibition capacity of the ligand and complexes followed the order of 3 > 2 > 1 > L1.