Coordination behaviour and biological activity studies involving theoretical docking of bis‐Schiff base ligand and some of its transition metal complexes

The Schiff base ligand 1,2‐bis(2‐vinylphenoxy)ethane‐4,6‐diaminopyrimidine‐2‐thiol derived from the condensation of 4,6‐diaminopyrimidine‐2‐thiol with bisaldehyde was synthesized and characterized. Coordination compounds of this Schiff base with transition metal cations Cd(II), Zn(II), Ni(II), Co(II), Mn(II), Cu(II) and Fe(III) were synthesized and characterized. Microanalytical data, magnetic moments, mass, 1H NMR and infrared spectra, molar conductance measurements and thermal analyses were used to confirm the structures of the obtained Schiff base ligand and its chelates. According to the data obtained, the 1:1 general stoichiometric formulae of chelates are given by [M(HL)(H2O)2]Cl2 (M = Cd(II), Zn(II), Ni(II), Co(II), Mn(II), Cu(II)) and [Fe(HL)(H2O)2]Cl3. The diffuse reflectance spectra and magnetic moment measurements suggest an octahedral geometry for the complexes. The bis‐Schiff base ligand and metal ions are coordinated in a tetradentate manner via OO and NN donor sites as confirmed by infrared spectra. These complexes were then subjected to antibacterial studies using Gram‐positive (Streptococcus pyogenes and Bacillus subtilis) and Gram‐negative (Proteus vulgaris and Escherichia coli) organisms. The ligand and metal complexes exhibited pronounced antimicrobial activity against both types of bacteria. A docking study was conducted to evaluate the nature of the binding of the ligand and the most biologically active complexes to protein active sites of these bacteria.