An Experimental Test of C−N Bond Twisting in the TICT State: Syn−Anti Photoisomerization in 2-(<i>N</i>-Methyl-<i>N</i>-isopropylamino)-5-cyanopyridine

Abstract

A previously untested essential consequence of the "TICT" (twisted internal charge transfer) interpretation of the nature of the "anomalous" excited state of p-dimethylaminobenzonitrile (1) and related compounds has now been verified: at -90 degreesC, the dual fluorescence of a desymmetrized analogue, 2-(N-methyl-N-isopropylamino)-5-cyanopyridine (2), in methanol (MeOH) is accompanied by syn-anti isomerization around the C-N bond, whereas its ordinary fluorescence in tetrahydrofuran is not.