MULTIPLE EMISSION OF N-(1-ANTHRYL)-PYRIDINIUM

The acceptor-substituted anthracene N-(1-anthryl)-2,4,6-trimethylpyrid inium shows dual fluorescence with a precursor-successor relationship which is most prominent in the intermediate temperature range, At 77K, only the short-wavelength band (anthracene-type fluorescence originat ing formally from S-2) remains. The additional red-shifted fluorescenc e band observed at higher temperatures is of charge transfer type, A c omparison of the radiative transition rates in absorption and emission suggests that structural relaxation leading to increased orbital over lap takes place in the excited state. This behaviour is unusual for a charge transfer state and is rationalized by the proposal of a bending motion (rehybridization of the nitrogen) induced by the increased ele ctron density within the pyridinium ring.