Theoretical and Experimental Investigation on Dipole Moment of Synthetized yt-Base in the Ground and Excited States

The electric dipole moment of yt-Baae calculated by the CNDO/S and JNDO/S method is µg = 3.42 D and µg = 3.74 D in the ground state and µe = 4.41 D and µe = 5.67 D in the first excited ππ*-state, respectively, µg and µe being nearly antiparallel. Measurements of absorption and fluorescence spectra of yt-Base in aprotic solvents of different polarity yielded µg = 3.8 D and µe = 4.3 D and the directions of dipole moments were found to be nearly antiparallel. This comparison may be considered as an indication for the ππ* character of the observable first excited state, although the CNDO/S- and JNDO/S-calculations predict a nπ*-state as the lowest lying excited state.