The macrocyclic effect and vasodilation response based on the photoinduced nitric oxide release from trans-[RuCl(tetraazamacrocycle)NO](2+)

Irradiation of trans-RuCl(cyclam)(NO)](2+), cyclam is 1,4,8,11-tetraazacyclotetradecane, at pHs 1-7.4, with near UV light results in the release of NO and formation of trans-Ru(III)Cl(OH)(cyclam)](+) with pH dependent quantum yields (from approximately 0.01 to 0.16 mol Einstein(-1)) lower than that for trans-RuCl(15]aneN(4))(NO)](2+), 15]aneN(4) is 1,4,8,12-tetaazacyclopentadecane, (0.61 mol Einstein(-1)). After irradiation with 355 nm light, the trans-RuCl(15]aneN(4))(NO)](2+) induces relaxation of the aortic ring, whereas the trans-RuCl(cyclam)(NO)](2+) complex does not. The relaxation observed with trans-RuCl(15]aneN(4))(NO)](2+) is consistent with a larger quantum yield of release of NO from this complex.