Synthesis and antibacterial studies of rhodium and iridium complexes comprising of dipyridyl hydrazones

Reactions of Cp*Rh and Cp*Ir dimers with the dipyridyl hydrazones such as picolinic (L1), nicotinic (L2) and isonicotinic (L3) have been reported here with the formulations [Cp*MCIL3](PF6) {where M = Rh (5) and Ir (6)}, [(Cp*MCl)(2)L1](PF6) {where M = Rh (7) and Ir (8)}, [(Cp*MCl)(2)L2Cl](PF6) {where M = Rh(9) and Ir(10)}, and [(Cp*MCl)(2)L3Cl](PF6) {where M = Rh (11) and Ir (12)} which resulted in a series of mono- and di-nuclear cationic complexes. The complexes have been characterized by various spectroscopic techniques. The solid-state structures of three complexes (5, 6 and 8) have been determined by single-crystal X-ray diffraction studies. These cationic complexes have been evaluated for the preliminary antibacterial activity towards four bacterial strains viz., Staphylococcus aureus; Bacillus thuringiensis; Escherichia coli and Pseudomonas aeruginosa by agar well diffusion method. Complexes have exhibited zone of inhibition over Bacillus thuringiensis; Escherichia coli and Pseudomonas aeruginosa strains while Staphylococcus aureus strain is resistant to the complexes 9-12. Surprisingly, these complexes are di-nuclear and trichloride complexes. (C) 2018 Elsevier B.V. All rights reserved.