Visible-Light-Triggered Release of Nitric Oxide from N-Pyramidal Nitrosamines

Although many organic/inorganic compounds that release nitric oxide (NO) upon photoirradiation (phototriggered caged-NOs) have been reported, their photoabsorption wavelengths mostly lie in the UV region, because X?NO bonds (X=heteroatom and metal) generally have rather strong p-bond character. Thus, it is intrinsically difficult to generate organic compounds that release NO under visible light irradiation. Herein, the structures and properties of N-pyramidal nitrosamine derivatives of 7-azabicyclo[2.2.1]heptanes that release NO under visible light irradiation are described. Bathochromic shifts of the absorptions of these nitrosamines, attributed to HOMO (n)LUMO (p*) transitions associated with the nonplanar structure of the N?NO moiety, enable the molecules to absorb visible light, which results in N?NO bond cleavage. Thus, these compounds are innate organic caged-NOs that are uncaged by visible light.