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-[RuIIICl(OH)(cyclam)]+ with pH dependent quantum yields (from ∼0.01 to 0.16 mol Einstein−1) lower than that for trans-[RuCl([15]aneN4)(NO)]2+, [15]aneN4 is 1,4,8,12-tetaazacyclopentadecane, (0.61 mol Einstein−1). After irradiation with 355 nm light, the trans-[RuCl([15]aneN4)(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]aneN4)(NO)]2+ is consistent with a larger quantum yield of release of NO from this complex.