The effects of molecular size, conjugation length, and competition with excimer formation on excited state intramolecular proton transfer (ESIPT) in conjugated polymers, in which the intramolecularly hydrogen-bonded moieties reside in the main chain, were examined. A large extent of T-electron delocalization is found to inhibit the ESIPT process. Excimer formation is found to be competitive with ESIPT in the polymers studied, whereas molecular size does not inhibit ES1PT.
The proton transfer reaction is ubiquitous in chemistry, biology, materials science, and other areas. The transfer of a hydrogen atom is the simplest of all atom transfer reactions and can be modeled by Marcus' theory [1]. Some molecules rearrange via an intramolecular proton transfer upon photoexcitation, a process known as excited state intramolecular proton transfer (ESIPT) [2-4], which was first described by Weller [5]. In the case of HBO (1, see Scheme 1), the hydrogen atom transfer generally occurs very rapidly, with time constants in the subpicosecond time regime [6]. The radiative portion of deactivation of the keto form occurs at wavelengths significantly Stokes shifted (> 6000 cm -~ ) from the absorption. After photoexcitation, a population inversion of the keto tautomer results, which enables