STRUCTURAL EFFECTS ON THE PHOTOPERSISTENCE OF ESTER-SUBSTITUTED AND PHENYL-SUBSTITUTED DBO-TYPE POLYCYCLIC AZOALKANES WITH CYCLOPROPYL AND NORBORNYL ANNELATION

The photophysical data for the polycyclic derivatives 1-7 of the photo reluctant diazabicyclo[2.2.2]oct-2-ene(DBO) has been determined. The d ata indicate that the photoreactivity (Phi(r)) does not depend on the endo-fused ring structures, whereas the fluorescence properties vary s ignificantly with such structural changes. Especially endo-hydrogen at oms of the fused cyclopropyl ring lower both the fluorescence quantum yields (Phi(f)) and the fluorescence halflives (tau(1/2)). The high ph otoreactivity of azoalkanes with alpha-substituted phenyl groups is si gnificantly lowered by steric interactions in these annelated derivati ves due to the higher rotational energy barriers to achieve the optima l planar radical-stabilizing conformation.