Ground- and Excited-State Absorption Spectra of 9-Acetoxy-10(4´-Acetoxy)phenylanthracenes

Abstract

The ground-(S0) and excited -(S1 and T1) state spectra of seven derivatives o f 9-acetoxy- 10(4´-acetoxy)phenylanthracene were determined in the region 50000 - 15000 cm -1 (200 - 660 nm). Comparison of these spectra to the unsubstituted molecule (anthracene) indicates the presence o f bathochromic shift and the steric effect. The substituents cause changes of positions of the energy levels (bigger shifts are noticed for low lying states) and also changes of the absorption intensities of some transitions. The steric hindrances between the phenyl-substituents and the anthracene skeleton are more pronounced if the - OAc(- Me) group or a heavy atom is introduced at position 2´o f the phenyl ring. Molecules possessing such substituents at the meso-position exhibit spectroscopic properties characteristic for a plane molecule in the S0 and S1 states; they show a better preservation of the mirror symmetry between the absorption and fluorescence spectra, lower Stokes shifts and the destabilization energies and bigger fluorescence quantum yields.