Excitonic nature of the dual fluorescence of 2,3-diazabicyclo[2.2.2]oct-2-ene and 1,4-dimethyl-(2,3-diazabicyclo[2.2.2]oct-2-ene)

Absorption, fluorescence excitation, and fluorescence spectra and the dependence of the degree of fluorescence polarization on the emission wavelength are measured for glass-like ethanol solutions of 2,3-diazabicyclo[2.2.2]oct-2-ene and 1,4-dimethyl-(2,3-diazabicyclo[2.2.2]oct-2-ene) at a temperature of 77 K. The analysis of the spectral polarization data shows that two excited electronic states S₁ and S₂ that contribute to the emission of the compounds are related to the exciton splitting and correspond to the symmetric (S₂) and antisymmetric (S₁) wave functions.