Synthesis, characterization, and antimicrobial activity investigations of ruthenium (II)-bipyridine complexes of ciprofloxacin derivatives

A series of ruthenium (II) complexes derived from the reaction between cis-bis (2,2 '-bipyridine) dichloro ruthenium (II) dihydrate and enaminone derivatives of ciprofloxacin were synthesized and fully characterized using elemental analysis, cyclic voltammetry and different spectroscopic techniques (Uv-vis, FTIR, NMR, mass spectroscopy, and X-ray photoelectron spectrometry (XPS)). The isolated compounds were tested for their antibacterial and antifungal activities against gram-negative and gram-positive bacteria. The FTIR data revealed that ciprofloxacin derivatives act as bidentate ligands through the pyridone carbonyl and the carboxylate oxygen atom. The UV-visible data showed that the charge transfer CT band is blue shifted upon the coordination of the ciprofloxacin derivatives compared to the CT band of the parent complex. The XPS results revealed the characteristic peaks of Ru-3p3/2 and Ru-3p1/2 as well as Ru-3d5/2 and Ru-3d3/2, which confirmed the assembly of the ruthenium (II) ciprofloxacin derivative complexes. Cyclic voltammetry data showed that the ciprofloxacin enaminone derivatives have a similar reduction potential for the Ru (II)/Ru (III) redox couple, and it revealed that the coordination of the ruthenium (II) ion altered the redox property of the ligands and enhanced their electron transfer rate. The electrochemical and the UV-visible results suggest that the ciprofloxacin derivative ligands are pi-acceptor ligands. Further, the complexes showed higher antibacterial activities than the parent ciprofloxacin antibiotic and did not show antifungal activities among the tested fungi strains.

Automated summary

A series of ruthenium (II) complexes derived from the reaction between cis-bis (2,2 '-bipyridine) dichloro ruthenium (II) dihydrate and enaminone derivatives of ciprofloxacin were synthesized and characterized. The complexes exhibited higher antibacterial activities compared to the parent ciprofloxacin antibiotic, and the enaminone derivatives were identified as pi-acceptor ligands.