Dual fluorescence of the isoquinolinium cation in methanol: time-resolved emission spectra and semiempirical calculations Original Research Article

The fluorescence behavior of the N-ethyl isoquinolinium (iso-NEQ) cation in viscous methanol is reported and discussed on the basis of time-resolved fluorescence spectra, polarization measurements and semiempirical calculations. Dual fluorescence results from two nearby excited states (S1 and S2) above 300 nm only at low temperature. The detection of an isoemissive point verifies this two-state model of the emission. We use the numerical self-consistent reaction field (SCRF) to include solute–solvent interactions for the calculations of the absorption transitions of iso-NEQ in methanol. We also involved the so-called supermolecular approach with three methanol molecules to reproduce the absorption transitions. The latter results are in good agreement with our experimental data.