Coordination behaviour, molecular docking, density functional theory calculations and biological activity studies of some transition metal complexes of bis-Schiff base ligand

Coordination compounds of Mn (II), Fe (III), Co (II), Ni (II), Cu (II) and Cd (II) ions were synthesized from reaction with Schiff base ligand 4,6-bis((E)-(2-(pyridin-2-yl)ethylidene)amino)pyrimidine-2-thiol (HL) derived from the condensation of 4,6-diaminopyrimidine-2-thiol and 2-(pyridin-2-yl)acetaldehyde. Microanalytical data, magnetic susceptibility, infrared and H-1 NMR spectroscopies, mass spectrometry, molar conductance, powder X-ray diffraction and thermal decomposition measurements were used to determine the structure of the prepared complexes. It was found that the coordination between metal ions and bis-Schiff base ligand was in a molar ratio of 1:1, with formula [M (HL)(H2O)(2)] X-n (M = Mn (II), Co (II), Ni (II), Cu (II) and Cd (II), n = 2; Fe (III), n = 3). Diffuse reflectance spectra and magnetic susceptibility measurements suggested an octahedral geometry for the complexes. The coordination between bis-Schiff base ligand and metal ions was through NNNN donor sites in a tetradentate manner. After preparation of the complexes, biological studies were conducted using Gram-positive (B. subtilis and S. aureus) and Gram-negative (E. coli and P. aeruginosa) organisms. Metal complexes and ligand displayed acceptable microbial activity against both types of bacteria.