Conformational equilibria in 1,2-diarylethylenes manifested in their emission in solution. Part 5. 2,6-Distyrylnaphthalene and related compounds

The emission spectra of the title compounds vary with the wavelength of the exciting light. These spectra can be described as superpositions, for each compound, of three sets of emission peaks which contribute to the overall spectra to an extent varying with the excitation wavelength. It is suggested that in solutions of each compound three modifications exist in a dynamic equilibrium. They have essentially similar but slightly shifted absorption and emission spectra, so that the fraction of exciting light absorbed by each modification varies with the wavelength of the exciting light. The three modifications are assigned to rotational conformers involving the two quasi-single styryl–naphthyl bonds. In 1,4-distyryl- and 1,5-distyryl-naphthalene, in which only one relatively unhindered conformer can be envisaged, no variation of the emission spectra with the excitation wavelength was observed.