Resolution of trans-1-(2-naphthyl)-2-phenylethene fluorescence in the presence of tri-n-butylamine into pairs of monomer and exciplex spectra. Selectivity in conformer quenching
Article
Saltiel, J, Choi, JO, Sears, DF et al. (1996). Resolution of trans-1-(2-naphthyl)-2-phenylethene fluorescence in the presence of tri-n-butylamine into pairs of monomer and exciplex spectra. Selectivity in conformer quenching
. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 118(32), 7478-7485. 10.1021/ja961340g
Saltiel, J, Choi, JO, Sears, DF et al. (1996). Resolution of trans-1-(2-naphthyl)-2-phenylethene fluorescence in the presence of tri-n-butylamine into pairs of monomer and exciplex spectra. Selectivity in conformer quenching
. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 118(32), 7478-7485. 10.1021/ja961340g
Fluorescence spectra of trans-1-(2-naphthyl)-2-phenylethene (NPE) obtained at different excitation wavelengths and tri-n-butylamine (TBA) concentrations in methylcyclohexane are resolved into four distinct components by application of principal component analysis with self-modeling. Two of the components are the NPE conformer fluorescence spectra, and the other two are the corresponding NPE·TBA exciplexes. Pure component combination coefficients are based on optimization of global (λ(exc)-independent) Stern-Volmer plots for the monomers and exciplex fluorescence plots for the exciplexes. Conformer-specific fluorescence quenching rate constants by the amine are obtained for the first time. These are indistinguishable from the corresponding exciplex formation rate constants. Fortuitously, the Stern-Volmer constants for the two singlet excited conformer/TBA interactions differ by only ~25%, revealing high conformer selectivity by TBA. This selectivity is consistent with the large shift between the λ(max) of the two exciplex fluorescence spectra which reveals the more favorable (2.9 kcal/mol) reduction potential of NPE(A), the less extended conformer.
