Control of thermal and photochemical reaction pathways by &z.sbnd;NO2 pendants in macrocyclic complexesThe redox photochemistry of Cu(10-methyl-1,4,8,12-tetraazacyclopentadecan-10-Y)2+, Y = NO2, NH2, in charge transfer and ligand field excited states

Abstract

Abstract The irradiation of Cu(10-methyl-1,4,8,12-tetraazacyclopentadecan-10-NO 2 )X + , X = halide, HCO 2 − , CH 3 CO 2 − and C 6 H 5 CH 2 CO 2 − , in deaerated CH 3 CN or CH 3 OH at 350 nm resulted in the reduction of the pendent NO 2 to NO. Flash photolysis revealed the formation of the nitroso products via the photo-induced oxidation of the axial ligand X − . Intermediates in a 10 ns–1 s time scale have been tentatively assigned as species formed by the addition of the X radicals to the NO 2 . Similar redox processes were observed when the irradiation of the complexes was carried out in the ligand field band, λ exc = 560 nm. Conversion of the ligand field excited states to X − to Cu(II) charge transfer excited state account for the photoreactivity of the former excited states.