A new homoleptic coordination compound of ruthenium and norfloxacin and its interaction with human serum albumin

This work presents a new coordination compound of ruthenium and the norfloxacin antibiotics, as well as its interaction with human serum albumin (HSA). The ESI HRMS spectrum of {[}Ru(nor)(3)] (nor = norfloxacinate, C16H17FN3O3-) displayed the protonated molecular ion at m/z 1057.3, while the HRMS/MS spectra displayed peaks at m/z 958.4 and 639.3 assigned to the gaseous phase norfloxacin adducts (Hnor)(3).H+ and (Hnor)(2).H+. Coordination to Ru(III) remarkably enhances the water solubility of norfloxacin. The complex absorption spectrum in aqueous medium is dominated by the norfloxacin transitions in the UV region but also displays a broad shoulder around 370 nm, which possibly overlaps with ligand-field transitions. Stern-Volmer analysis of human serum albumin (HSA) fluorescence quenching by {[}Ru(nor)(3)] showed that both dynamic and static mechanisms contribute to the quenching. Lifetime measurements demonstrated that the predominance of one pathway over the other depends on temperature variations. Finally, the analysis of thermodynamic parameters leads to the conclusions that the interaction of the novel complex with HSA is spontaneous and that this interaction occurs through the formation of hydrogen bonds and van der Weals forces (Delta H = -259.2 kJ/mol and Delta S = -779.9 kJ/mol.K). (C) 2015 Elsevier B.V. All rights reserved. (AU)