Excited state structure of N-(4-cyanophenyl)carbazole by time-resolved infrared absorption spectroscopy

Abstract

Nanosecond time-resolved infrared absorption spectroscopy has been used to study the charge transfer characteristics of the title compound in electronically excited states. The transient infrared bands observed at 2090 cm-1 and 2060 cm-1 have been attributed to the CN stretch modes in the first excited singlet and triplet states of the molecule. These frequencies are in conformity with enhanced charge separation in the excited states. Comparison of the present result with the existing data for 4-(N,N-dimethylamino) benzonitrile has indicated that the CN stretch frequency is not a direct measure of the polarity of the excited states of these molecules.