Photoinduced intramolecular charge separation ofp-N,N-dimethylamino-p′-cyano-diphenylacetylene in polar solvents

By using picosecond transient absorption measurement techniques, we have investigated the intramolecular charge separation process and the dynamic spectral shift ofp-N,N-dimethylamino-p′-cyano-diphenylacetylene in various polar solvents. In alcohols the spectral shift of the intramolecular charge-separated state was observed in the tens of picosecond time scale, while in aprotic polar solvents the spectral shift was too fast to measure with our time resolution. The dipole moment of the intramolecular charge-separated state, which gives a transient absorption spectrum in the red region, is about 36 D.