Interaction of two π-electron systems: Spectroscopy of 9,10-dihydroanthracene

Abstract

The absorption fluorescence, and excitation spectra of 9,10-dihydroanthracene in methylcyclohexane-isopentane (MCH-IP) glass and in n-heptane (Shpol'skii matrix) are reported. The fluorescence origin is found to be red-shifted from the excitation origin; this has been interpreted as due to exciton splitting of the 1B2u state of benzene with the forbidden state lying lower in energy. A comparison of the one-photon absorption with the two-photon fluorescence excitation spectrum supports this assignment. A theoretical estimate by the CNDO/S-CI method is in general agreement with the observations Further, it is observed that in fluid solution the emission becomes blurred; this is tentatively ascribed to a conformational relaxation from a puckered to a nearly planar conformation. In the planar rigid n-heptane matrix at 77 K, the ground state is forced to a planar conformation. © 1987 American Chemical Society.