Structural, spectral, and photoreactivity properties of mono and polymetallated-2,2′-bipyridine ruthenium(II) complexes

Abstract

Polymetallated-2,2′-bipyridine–ruthenium(II) complexes exhibit photosensitization properties and can enhance optically induced NO release, thus modeling multi-site catalysts. Two novel ruthenium-nitrosyl complexes [RuCl2LA(NO)]PF6 (herein called RuLANO, LA = 2,6-bis[(aniline)methyl]-pyridine) and [RuCl2(NO)({Ru(bpy)2}2-μ-LB)](PF6)5 (herein called Ru3LBNO, LB = 2,6-bis[(1,10-phenantroline-5-amine)methyl]-pyridine) were prepared and structurally characterized (1H-, 13C-, DEPT-135 NMR, FTIR, UV–Vis, elemental analysis, ESI-HRMS, and single crystal x-ray diffraction). RuLANO showed a trans configuration of the chloride ligands, and photo-release of chloride is the major process upon irradiation of RuLANO at 377 nm, along with some NO dissociation to a small extent. In contrast, the trinuclear ruthenium complex Ru3LBNO was found to be photo-inactive with irradiation between 377 and 447 nm (region of absorption of the {Ru(bpy)2(phen)}2+ chromophore) in the same conditions of RuLANO. This result agrees with the strong stabilization of Rucentral dxy, dxz, and dyz orbitals as shown by calculations using density functional theory (DFT), as well as with the electrochemical response, which supports that there is no major electronic communication between the central and the peripherals ruthenium ions in the trinuclear complex.