Arene ruthenium, rhodium and iridium complexes containing N∧O chelating ligands: synthesis, antibacterial and antioxidant studies

The reaction of [(arene)MCl2](2) with ligands 4-hydroxy-benzhydrazide (L1) and 3-methoxy-benzhydrazide (L2) leads to formation of cationic complexes 1-6 having the general formula [(arene)M(L)Cl](+) {arene = p-cymene, M = Ru; arene = Cp*; M = Rh/Ir; L = L1 and L2}. The reaction of [CpRu(PPh3)(2)Cl] with L1 and L2 yielded cationic complexes that have been formulated as [CpRu(L)PPh3]Y {Y = Cl (7), Y = PF6 (8)}. The molecular structures of 1, 2 and 4 revealed that these complexes adopt typical three-legged "piano stool" geometry. The arene ring occupies the apex of the stool, terminal chloride and N,O-bidentate ligands are coordinated to the metal center at the base of the stool. The antibacterial activity of the ligands and complexes was evaluated on Gram-positive S. aureus, B. thuringiensis and Gram-negative E. coli, P. aeruginosa strains; some complexes exhibit moderate antibacterial activity towards gram-positive bacteria. The antioxidant studies of these complexes have been carried out, and the results showed that these complexes have strong DPPH-scavenging properties.