External electric field effects on absorption and fluorescence of anthracene–(CH2)n–naphthalene bichromophoric molecules doped in a polymer film

Methylene-linked bichromophoric molecules of naphthalene and anthracene, i.e., 9-anthryl–(CH2)n–1-naphthyl exhibit a very efficient photoexcitation energy transfer (EET) from the naphthalene to anthracene moieties in a polymer film, resulting in the observation of only the anthracene-like fluorescence even for excitation of the naphthalene moiety. Electrofluorescence spectra of the linked compounds are very different from those of a mixture of naphthalene and anthracene, indicating that methylene chain plays a significant role in excitation dynamics and its electric field effect. At high concentrations, where both monomer fluorescence and excimer fluorescence of anthracene are observed, the excimer fluorescence of the linked compounds is enhanced by an electric field, whereas the monomer fluorescence is quenched by an electric filed, suggesting that the intermolecular excimer formation is remarkably enhanced by an electric field in the linked compounds.