Synthesis, structure and biological evaluation as antibacterial agents of Ru(II)-p-cymene-aryldicyclohexylphosphine complexes

Abstract

The syntheses of two neutral complexes with formula [Ru(η6-p-cymene)(P(Cy)2Ar)Cl2], where P(Cy)2Ar = dicyclohexylphosphine, Ar = Ph (1) and 4-(N,N-dimethylamino)phenyl (4-dma-ph) (2) were performed. Both complexes were fully characterized by molar conductivity, elemental analysis and spectroscopic methods. The molecular structures of 1 and 2 that were elucidated by single crystal X-ray diffraction show that both structures adopt the pseudo-octahedral geometry characteristic of organoruthenium species. Absorption spectra and electrochemical behavior of the complexes were also evaluated and their results were supported by DFT analysis. Both complexes were active against tested bacterial strains: Gram-positive (Staphylococcus aureus) and three species Gram-negative (Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa). 2 shows higher bacterial growth inhibition activity compared to 1, which might be due to its molecular structure that could facilitate the interaction among this complex and the biological environment. These results agreed with the Langmuir monolayer and molecular docking studies. 1 and 2 change the pressure isotherms of 1,2-dioleoyl-sn-glycero-3-phosphatidylglycerol, a phospholipid used as a bacterial membrane model. Molecular Docking studies performed with S. aureus and E. Coli bacteria using the Topoisomerase IV (4URN) and DNA Gyrase as receptor (1KZN), showed that both complexes have potential antimicrobial effects compared to the ciprofloxacin.