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

• Published in: Chemistry : a European journal 2012-01, Vol.18 (4), p.1127-1141
• Main Authors: Karaki, Fumika, Kabasawa, Yoji, Yanagimoto, Takahiro, Umeda, Nobuhiro, Firman, Urano, Yasuteru, Nagano, Tetsuo, Otani, Yuko, Ohwada, Tomohiko
• Format: Article
• Language: English
• Subjects: cage compounds; Chemistry; cleavage reactions; Cyclization; Light; Models, Molecular; Molecular Structure; Nitric oxide; Nitric Oxide - chemistry; nitrogen oxides; nitrosamines; Nitrosamines - chemistry; photolysis
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201101427

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 π‐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 (π*) 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. A visible difference: Nitrosamine derivatives of 7‐azabicyclo[2.2.1]heptanes undergo NNO bond cleavage upon exposure to visible light at wavelengths longer than 420 nm, thereby releasing NO. Bathochromic shifts of the absorptions of these nitrosamines are attributed to HOMO (n)–LUMO (π*) transitions associated with the nonplanar structure of the NNO moiety (see figure).