A study of vibronic structures in the optical spectra of oligo(thienylene ethynylene)s

At the low temperature, hidden vibronic structures were successfully resolved in the absorption spectra of oligo(thienylene ethynylene)s 2–4. Identification of the lowest energy absorption band aids the assignments of the vibronic structures in these molecules. The emission λmax values were also found to be slightly red-shifted at the low temperature, indicating the adoption of a more planar conformation. The temperature-induced change in molecular conformation appeared to be dependent on the conjugation length of the molecules.