The triple fluorescence of benzanilide and the dielectric medium modulation of its competitive excitation

Abstract

The fluorescence of the benzanilide molecule at 298 K is inferred to consist of three independent electronic transitions associated with the single ground-state molecular species. F 1 (λ max340 nm), the normal fluorescence is observed weakly and is ascribed to an n,π*,-π,π* mixed state. F′ 2 is ascribed to the proton-transfer imidol tautomer fluorescence (previously reported) with unresolved λ max (inferred at ≈460 nm). F″ 2 is ascribed to a charge-transfer state fluorescence to the ground state, and occurs as a resolved CT transition in tetrahydrofuran at λ max 520 nm. Comparison of the spectra of N-methylbenzanilide exhibiting only F 1 and F″ 2 (CT) permitted the analysis of the benzanilide spectra.