Internal rotation in [p-(dialkylamino)benzylidene]malononitriles

Abstract

The dynamic structures of [p-(dialkylamino)benzylidene]malononitriles have been investigated by 1H nmr, and the kinetic and thermodynamic parameters for the partial rotation of the malononitrile moiety were obtained and those of the dialkylamino group were estimated. The rate of rotation of the above rotors were found to be of the order of ~104 s−1 and ~107 s−1, respectively.

Spectroscopic investigation of cyanovinyl-diethylaniline dyes in solutions

“…This means that the dye molecules relax from the excited S,-state by an intrinsic barrierless transition. Only the solute-solvent friction slows down the torsional deactivation [8][9][10][11][12][13][14][15][16][17].…”

“…thought to be due to some charge transfer in the excited state [11,17,18,28] according to scheme 1, where R=H for DCVA and R = CN for TCVA. A complete electron transfer -as indicated by the formula at the right-hand side of scheme 1 -would result in a change of the dipole moments of /* c -//g« 1.1 X 10~2 8 C m = 34 D by excitation (charge separation %0.7 nm).…”

“…The dyes belong to a class of organic compounds known as molecular rotors [8][9][10][11] which have great importance as fluorescence probes of the flexibility of surrounding media [2,[8][9][10][11][12][13][14][15][16][17]. Some dicyanovinyl-alkylaniline dyes were ap- plied to determine static and dynamic changes of free volumes and torsional rigidities of polymers [9][10][11][12][13][14][15][16].…”

“…DCVA and TCVA are disubstituted benzenes of the type D-Ph-A with an electron donor D (diethylamino group) and an electron acceptor A (dicyanovinyl or tricyanovinyl group) [8,17]. The electronic excitation of these dyes is accompanied by a large increase in the polarity due to changes in the charge distribution (internal charge transfer) [8][9][10][11][12][13][14][15][16][17][18][19][20].…”

“…The electronic excitation of these dyes is accompanied by a large increase in the polarity due to changes in the charge distribution (internal charge transfer) [8][9][10][11][12][13][14][15][16][17][18][19][20]. The ground-state and excited-state dipole moments, // g and H e , of some dicyanovinyl-alkylaniline dyes were determined in refs.…”