Antimicrobial selectivity of ruthenium, rhodium, and iridium half sandwich complexes containing phenyl hydrazone Schiff base ligands towards B. thuringiensis and P. aeruginosa bacteria

Abstract

A series of new hydrazone mononuclear complexes of the type [(arene)MLCl]PF6 (M = Ru, Rh, Ir) have been synthesized in this study. All these complexes were fully characterized with the help of FT-IR, UV–Vis, mass and NMR spectroscopy. The molecular structures of representative complexes (1, 2, 7 and 8) were established by single crystal X-ray diffraction study. The molecular structures of the complexes revealed typical piano stool geometry around the metal center in which the ligand acts as NN′ donor chelating ligand. In the case of complexes (1–3), the ligand coordinates to the metal by using both the pyridine nitrogen atoms forming a six membered metallocycle whereas in complexes (4–9) one hydrazone nitrogen atom and one pyridine nitrogen atom coordinates to the metal ion forming a five membered metallocycle. These compounds were evaluated for their in vitro antibacterial activity by agar well diffusion method against two Gram-negative bacteria Escherichia coli, Pseudomonas aeruginosa, and two Gram-positive bacteria Staphylococcus aureus, Bacillus thuringiensis. Results show that all the complexes inhibit the growth of bacteria.