A DFT study of cis-[Ru(NO)(NO2)bpy(dye)2]+ complexes as NO donors

The synthesis and characterization of a new complex, cis-[Ru(NO)(NO2)bpy(AO)2](PF6)2, was reported, and the release of NO from ruthenium-nitrosyl complexes with dye ligands was investigated using DFT and TDDFT methods. The complexes are cis-[Ru(NO)(NO2)bpy(dye)]n+, where the dye is either proflavine (1), acridine orange (2), neutral red (3), resorufin (4), thionol (5), or methylene violet (Bernthsen) (6). The optimized structures are in agreement with the experimental data of analogue complex from the literature. Simulated UV–Visible spectrum of complex 2 showed good agreement with the experimental results. The calculated electron affinities (EA) indicated that the N-coordinated complexes 1–3 should be more easily reduced and that this reduction weakens the Ru–NO bond, thus facilitating the NO release. Reduced complexes (Ru-NO0) presented lower bond dissociation energies (BDE) than the complexes (Ru-NO+). Complexes 1–3 showed the lowest BDE. This suggests a lower energy cost to release NO, and therefore, the N-coordinated complexes are the most promising NO donors among the investigated complexes.