Exploring weak interactions to assemble a nitrosyl–ruthenium compound able to release NO under visible light irradiation

This work reports on a novel nitrosyl–ruthenium complex bearing the azanaphthalene ligand quinazoline (qui) in its coordination sphere. The product crystallizes with an additional quinazoline molecule, yielding the compound cis-Ru(bpy)₂(qui)NO](PF₆)₃ · (qui). This feature leads to an absorption band at λ_max = 430 nm in CH₃CN and λ_max = 420 nm in phosphate buffer, which promotes the photorelease of nitric oxide under visible light irradiation (λ > 400 nm), in 1 ethanol:1 water (v/v) mixture or under physiological pH. Both the intensity and energy of this transition are dependent on solvent and solution pH, suggesting that the transition has a charge transfer nature, and that the association of the second quinazoline molecule with the complex is driven by weak interactions, possibly of the π-stacking type.