Viscosity Effect on the Fluorescent and Conformational Properties of 2-N-Piperidino-5-(2',2'-dicyanovinyl)thiophene

摘要

The mechanism of deactivation of the electronic excitation energy of 2-N-piperidino-5-(2',2'-dicyanovinyl) thiophene is studied by the methods of fluorescence and quantum chemical calculations. The increase in the fluorescence quantum yield from 0.0004 in n-hexane at room temperature to 1 in an EPA mixture at 77 K is determined by an increase in the viscosity (rigidity) of the medium hindering the rotation of molecular fragments. The efficient nonradiative process in a molecule with the probability ≤2.5 * 10~(11) s~(-1) results mainly from rotation about the C12-C13 bond and the transition to an intermediate state with a low-lying energy level.