Spectroscopic probes. The effect of polymer chain on photophysical properties
of molecules exhibiting the existence of the TICT state.
Part I. Photostationary studies
Polimery 2000, No 11-12, 792
SummaryAbsorption and dual fluorescence spectra (originating from locally excited state (LE) and twisted intramolecular charge transfer (TICT) states) are presented for six molecule residues, viz., 4-(N,N-dimethylamino)benzoate (DMAB), 4-(N,N-diethylamino)benzoate (DEAB), 4-(N-pyrolidine)benzoate (PYR), 4-(N-piperidine)benzoate (PIP), 4-(N-morpholine)benzoate (MOR) and 4-(N-2,6-dimethylmorpholine)benzoate (2,6-DMM) used as spectroscopic probes. The probes were either simple (ethyl or n-butyl) esters or were attached covalently to the polystyrene chain (Table 1, formula I) and the fluorescence properties of the free and polymer-bonded fluorophores were intercompared. Both „free” probes and probes attached to the PS chain exhibit double fluorescence. Comparative studies of the spectra disclosed a considerable effect of preorientation of the molecules in the ground state on spectroscopic properties. The ground state twisting the donor with respect to the acceptor can exert an extensive effect on the ground state charge distribution. The close vicinity of the polymer chain is very likely to affect the distribution of conformers in this state and as a result cause (Figs. 1–7): (i) the bathochromic shift of the absorption and emission spectra, (ii) broadening of the absorption bands in the electronic absorption spectra, (iii) red edge (REE) and blue edge (BEE) effects in the emission spectra, and (iv) changes in the positions of emission maxima in the LE and TICT fluorescence spectra.