Ruthenium(II)-nitrosyl polypyridinyl Complexes: from NO/ON Isomerization to NO delivery

Abstract

Ruthenium-nitrosyl (Ru II (NO)) complexes are stable in the dark, but exhibit a unique photoreactivity which can lead either to a solid state isomerization from Ru II (NO) to Ru II (ON), or to a nitric oxide (NO·) release in solution. From our recent discovery of a high yield of isomerization (> 92%) in [Ru II (py) 4 Cl(NO)](PF 6 ) 2 , we have developed a computational strategy aimed at designing switchable nonlinear optical (NLO) material with high contrast (large difference in the on / off NLO response) in the solid state. Our synthetic targets are terpyridine based Ru II chromophores in which various substituents can be introduced to adjust the NLO response which, at best, should be vanishing in the off state. Alternatively, these complexes can undergo a photo-induced NO· release in solution, a possibility which becomes increasingly appealing in relation to the discovery of the numerous biological roles of NO·, in the context of the emergence of the photodynamic therapy. A promising fluorene-terpyridine Ru II( NO) complex was investigated, which could find an additional interest in relation to its capability for releasing NO· by a two-photon absorption process.