Synthesis and molecular structure of arene ruthenium(II) complexes containing benzhydrazone derivative ligands with antibacterial and antioxidant properties

Abstract

A suitable method for the synthesis of ruthenium(II) arene benzhydrazone complexes (1–6) of the general formula [(η6-arene)Ru(L)Cl] (arene = p-cymene or benzene; L= bidentate substituted benzhydrazone derivatives) has been described. The composition of all the complexes have been established by IR, UV-Vis and NMR spectroscopies and ESI-MS. Ruthenium precursors [(η6-arene)RuCl2]2 (arene = p-cymene or benzene) on reacting with benzhydrazone derivative ligands (L1, L2 and L3) resulted in the formation of mononuclear neutral complexes (1-6). All the neutral complexes were further reacted with NaN3 to yield azido complexes (7-12). Then, the binding modes of the benzhydrazone derivatives to the metal center for complexes (1, 5, 6, 7 and 9) have been confirmed by single-crystal X-ray diffraction studies. Further, their in-vitro antibacterial activity against gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli, Klebsiella pneumoniae) strains have been evaluated for the complexes (1-6) and their ligands. An anti-bacterial study revealed that complex 1 and complex 6 have magnificent activity against S. aureus, E. coli and K. pneumoniae. For antioxidant properties, all the complexes showed a higher percentage of DPPH radical scavenging activity than the ligands.