Decay times of 4-(dimethylamino)benzonitrile in acetonitrile and conclusions on entropy of activation

From picosecond decay times of 4-(dimethylamino)benzonitrile (DMABN) and 4-(dimethylamino)benzoic acid ethyl ester (DMABE) in acetonitrile (Ref. [1]), a conclusion on entropy effects cannot be made because of large uncertainties of the data. The planarized 1-tert-butyl-6-cyano-1,2,3,4-tetrahydroquinoline (NTC6) as a model for a planar intramolecular charge transfer (ICT) state and the influence of pretwist and size of the amino group is also discussed. For DMABE excited state absorption spectra show a decay of the locally excited (LE) and a rise of the ICT state of 1.0 ps, posing the question whether the lowest excited singlet state is of Lb or La character.