Remarkable oxidizing ability of triplet excited states of tetrazines produced by photosensitization with Ru(bpy)3(2+).

An efficient energy transfer from Ru(bpy)3(2+)* (bpy = 2,2'-bipyridine, * denotes the excited state) to tetrazines occurs to yield the triplet excited states of tetrazines, which have much longer lifetimes and higher oxidizing ability as compared with those of Ru(bpy)3(2+)*.