PHOTOISOMERIZATION STUDIED BY STEPWISE 2-COLOR 2-PHOTON EXCITATION .2. ALPHA-(10''-CYANOANTHRACEN-9''-YL)ETHYL SPIRO[CYCLOPROPANE-1,9'-FLUORENE]-2-CARBOXYLATES

Photoisomerization of alpha-(10 ''-Cyanoanthracen-9 ''-yl)ethyl spiro[ cyclopropane-1,9'-fluorene]-2-carboxylates (CA-1 reversible arrow CA-2 ) in benzene has been studied by stepwise two-color two-photon excitat ion methods. The quantum yields of the T-1 depopulation by stepwise tw o-photon excitation and moreover those in the presence of naphthalene have been determined in addition to the photophysical parameters for b oth CA-1 and -2. Assuming some reasonable hypotheses, the detailed rea ction mechanism has been established in comparison with the case of an thryl-substituted derivatives (An-1 and -2).