QUANTITATIVE STUDY OF DUAL FLUORESCENCE FROM S-CIS AND S-TRANS CONFORMERS OF TRANS,TRANS-2,4-DIPHENYL-1,3-BUTADIENE

The fluorescence spectra of trans, trans-1,4-diphenyl-1,3-butadiene (DPB) are strongly excitation wavelength dependent in the extreme red onset region of the absorption spectrum as a result of a ground-state conformational equilibrium (Wallace-Williams, S. E.; Moller, S.; Goldbeck, R. A.; Hanson, K. M.; Lewis, J. W.; Yee, W. A.; Kliger, D. S. J. Phys. Chem, 1993, 97, 9587). The fluorescence spectrum of the minor conformer s-cis-DPB is obtained by applying a chemometric method principal-component analysis-self-modeling spectral resolution to the observed fluorescence spectral mixtures. The relative fluorescence contributions of the s-cis and s-trans conformers of DPB are determined quantitatively, and the conformer excitation spectra are obtained from an excitation-emission matrix approach. The individual conformer absorption spectra for the red onset wavelength region are calculated from the excitation spectra and the observed fluorescence quantum yields.