Solvent effects on absorption and fluorescence spectra of diphenyltriafulvenes. Three modes of dipole moment variation upon excitation

Three representative diphenyltriafulvenes, 4,4′-dicyano-1,2-diphenyltriafulvene (I), hexaphenyltriapentafulvalene (II) and 10-(2,3-diphenylcyclopropenyliden)-anthrone (III) have been investigated. On excitation, the dipole moment of I decreases and reverses sign, i.e., from a value of 7.9 D in the ground state to a value of about -5.3 D in the first excited electronic state. That of II remains unchanged at 6.3 D, and that of III increases from 8.5 D to about 26 D. The Onsager radius of 1 was found to be about 8.7 Å and that of IIi, about 12 Å.