SPECTROSCOPIC STUDIES OF THE SINGLET AND TRIPLET EXCITED-STATES OF SOME SUBSTITUTED BIPHENYLENES

The steady-state and time-resolved spectroscopy of a series of substituted biphenylenes was probed to assess their possible application as photoreceptors in a liquid crystal-based optical switch. Their singlet-singlet and triplet-triplet absorption spectra were recorded, and the rates of their radiative and nonradiative relaxation processes were measured. In no case could a triplet biphenylene be detected following direct irradiation even when the substituent is expected to enhance intersystem crossing. Consequently, these compounds will not be suitable for application as photoreceptors that require triplet-state formation.