Synthesis, structural characterization, antibacterial activity and computational studies of new cobalt (II) complexes with 1,1,3,3-tetrakis (3,5-dimethyl-1-pyrazolyl)propane ligand

Abstract

Two new mono- and dinuclear Co(II) complexes namely [Co(tdmpp)Cl2]2·H2O (1) and [Co2(tdmpp)Cl4] (2) (where tdmpp = 1,1,3,3-tetrakis(3,5-dimethyl-1-pyrazolyl)propane) were prepared by one-pot reactions in methanol as a solvent. These compounds have been characterized by single crystal X-ray diffraction, elemental analysis, infrared spectroscopy, antibacterial activity and computational studies. In both complexes, Co (II) atom is tetrahedrally coordinated by two N atoms from one of the chelating bidentate bis(3,5-dimethylpyrazolyl)methane units of the tdmpp ligand and two Cl as terminal ligands. In these structures, the neighboring [Co(tdmpp)Cl2]2·H2O (1) and [Co2(tdmpp)Cl4] (2) molecules are joined together by the intermolecular CH⋯Cl hydrogen bonds to form a 1D chain structure. As a consequence of the intermolecular CH⋯π interactions these chains are further linked to generate a two-dimensional non-covalent bonded structure. The in vitro antibacterial activity studies of the free tdmpp ligand, compounds 1 and 2 show that the ability of these compounds to inhibit growth of the tested bacteria increase progressively from tdmpp to the dinuclear complex 2. Molecular-docking investigations between the five standard antibiotic, free tdmpp ligand, title complexes and five biological macromolecule enzymes (receptors) were carried out from using Autodock vina function. The results of docking studies confirmed that the metal complexes are more active than the free ligand. This is consistent with the results obtained by the antibacterial activities of these compounds.