Intramolecular photo-driven charge transfer in a series of pyridyl substituted phenyloxazoles. Structural relaxation in meta-substituted ethylpyridinium derivative of phenyloxazole

A series of pyridyl (pyridinium) substituted benzoxazoles were studied by steady state absorption, fluorescence spectroscopy, time-resolved fs pulse absorption and polarization quantum–chemical calculations. The spectral kinetic parameters the fluorophores in MeCN EtOAc obtained experimentally calculated means DFT TDDFT methods. scheme including four transient excited states was proposed for interpretation differential kinetics charged fluorophores. Expressions describing actual graphs, decay associated spectra, species-associated spectra derived. charge shift step found to be dependent on average solvation times. followed formation twisted conformer 1-ethyl-3-(5-phenyloxazol-2-yl)pyridinium 4-methyl-1-benzenesulfonate EtOAc. Conformational analysis confirms a large amplitude motion meta-substituted ethylpyridinium group as an additional structural relaxation path producing abnormally Stokes shift.