Synthesis, Characterization and Reactivity of Nitrosyl Ruthenium Complexes with the Non-stereoidal Anti-inflammatory Diflunisal

Abstract

The Na 2 [Ru(NO)Cl 3 (df)] (I) and cis-[Ru(NO)(df)(cyclen)]Cl 2 (II) complexes (df=diflunisal (5-(2,4-difluorophenyl)-2-hydroxybenzoic acid, cyclen=1, 4, 7, 10-tetraazacyclododecane) have been synthesized and characterized by elemental analysis, electronic (UV-Vis) and vibrational (FTIR) spectroscopic techniques. FTIR data suggests different modes of coordination of the ligand diflunisal in these complexes, i.e., coordinated in the bidentate form in the compound I and in the monodentate form in the compound II, and that df is coordinated to ruthenium by carboxylate group in a monodentate mode for both complexes. The FTIR spectra also display v(NO) at 1880 cm -1 and 1892 cm -1 for I and II, respectively, indicating a nitrosonium (NO + ) character. Electronic spectra suggest that df is coordinated to the metal center in both complexes in catecholate form. Detailed electrochemical studies showed that complexes I and II display {RuNO} 6/7 process at -420 mV and at -400 mV (vs. Ag/AgCl) respectively, and df ligand is oxidized at 1120 mV and at 770 mV, respectively. Controlled potential electrolysis at -750 mV or chemical reduction with Zn(Hg) amalgam results in NO release from both complexes.