The "excited state C-C bond cleavage-luminescence" phenomenon of a biphenyl-substituted methylenecyclopropane triggered by intermolecular energy transfer from triplet benzophenone.

Existence of the "excited state C-C bond cleavage-luminescence" phenomenon was demonstrated by utilizing intermolecular energy transfer from the excited-triplet benzophenone to 2,2-di(4-biphenylyl)-1-methylenecyclopropane (3). An excellent linear relationship between the intensity of the excitation laser light and that of luminescence clearly shows that formation of the corresponding excited trimethylenemethane biradical (3)4˙˙* proceeds via a one-photon route.