Spectroscopic probes. Influence of polymeric chain on photophysical
properties of molecules exhibiting the presence of the tict state.
Part II. The kinetics
Polimery 2001, No 1, 29
Fluorescence from the initially excited singlet state (LE) and the twisted intramolecular charge transfer (TICT) state of 4-(N,N-dimethylamino)benzoate (DMAB), 4-(N,N-diethylamino)benzoate (DEAB), 4-(N-pyrrolidine)benzoate (PYR), 4-(N-piperidino)benzoate (PIP), 4-(N-morpholine)benzoate (MOR) and 4-(N-2,6-dimethylmorpholine)benzoate (26DMM) were compared with the free and polystyrene bound chromophores. Adaptation of Grabowski's TICT hypothesis allows to calculate the activation energy for TICT state formation, the back-reaction TICT<=>LE, and the thermally activated TICT fluorescence. The polymeric chain essentially does not change the activation energy (E1) for TICT state formation, indicating that the polymeric chain does not change the microscopic viscosity in the range affecting measurable changes in the TICT<=>LE equilibrium. Experimental results suggest that the polymer chain affects only the vibrational relaxation of the tested molecules without any significant effect on the thermodynamics of the TICT and LE states equilibrium. The fluorescence lifetime and fluorescence anisotropy measurements additionally support these conclusions.
Keywords: spectroscopic probes, dual fluorescence, LE and TICT states, kinetic of formation, effective volume, polymeric chain effect