title: Fluorescence enhancement of covalently linked 1-cyano-1,2-diphenylethene chromophores with naphthalene-1,8-diyl linker units: analysis based on kinetic constants.
abstract: The fluorescence enhancement effect of covalently fixed fluorescent chromophores has been investigated by means of kinetic analysis of decay rate constants and theoretical calculations. Derivatives of 1-cyano-1,2-diphenylethene dimer have a distorted cyclic structure when both ends are clipped with two naphthalene-1,8-diyl linker units. In contrast to the reference monomer derivative, which exhibits only slight fluorescence in solution (Φf < 0.01, τf < 0.1 ns), the dimer derivative shows high fluorescence quantum yield (Φf = 0.55) and long lifetime (τf = 20.6 ns) in dilute solution owing to suppression of the nonradiative decay process (knr = 0.022 ns(-1)). A V-shaped derivative with a covalent linker on one side showed moderate quantum yield and lifetime (Φf = 0.12, τf = 4.9 ns). According to the wavelength shifts of the absorption/fluorescence bands and theoretical calculations by time-dependent density functional theory (TD-DFT), we propose an H-aggregate-type excimer interaction.
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510 (Japan), Fax: (+81) 75-383-2739.
authors.forename: Takashi
authors.initials: T
authors.lastname: Hirose
authors.forename: Yohei
authors.initials: Y
authors.lastname: Tsunoi
authors.forename: Yuya
authors.initials: Y
authors.lastname: Fujimori
authors.forename: Kenji
authors.initials: K
authors.lastname: Matsuda
keywords: density functional calculations; fluorescence; intramolecular excimer; photophysics; pi interactions