Structure, chemical and photochemical reactivity and biological activity of some ruthenium amine nitrosyl complexes

Through spectroscopic (X-ray, Infrared, H-1-NMR, EPR, UV-vis) and electrochemical (cyclic voltammetry, differential pulse polarography) data and quantum mechanical calculations, the formulation [Ru(II)NO+] was attributed to a series of new ruthenium(II) amine compounds. A remarkable stability of the Ru(II) relative to Ru(III) was observed upon coordination to NO. The presence of nitrosyl in the coordination sphere results in dramatic implications in the lability, acidity and redox properties of the ligand trans to NO. These effects are higher than expected just on the basis of one unity increment in the metal center charge. Based on molecular orbital (MO) analysis and on reduction product analysis, the,site of the reduction [Ru(NO)](3+) + e(-) --> [Ru(No)](2+) was assigned to the NO ligand. The dissociation of the coordinated NO0 is dependent on the trans effect and trans influence of the trans ligand L. Irradiation of the nitrosyl complexes with 300-350 nm light results in NO aquation and formation of the corresponding aquaruthenium(III) complex, i.e. [GRAPHICS] Irradiation in the visible region (400-500 nm) did not result in any observable reaction in solution; however, at low temperature and in the solid state, evidence in favor of the formation of linkage isomers has been obtained. The hypotensive properties of trans [Ru(NO)(NH3)(4)(P(OC2H5)(3))](PF6)(3) and trans-[Ru(NO)Cl(cyclam)](ClO4)(2) have been demonstrated in mice and rats. (C) 2002 Elsevier Science B.V. All rights reserved.