Two-Photon Absorption and Excited-State Energy-Transfer Properties of a New Multibranched Molecule

This paper presents a molecular design for a two-photon absorbing structure, which contains a two-dimensional molecular architecture with four arms and one bridging unit, each of these segments having an extended π-conjugation and capable of producing two-photon absorption in different spectral ranges. Two chromophore units of a triphenylamine derivative dye, (N, N-di[4-{4-(5-[4-tert-butylphenyl]-1,3,4-oxadiazol-2-yl)styryl}phenyl]amino)benzene, were linked with a π-conjugated di-2-thienylethenylene bridging unit to form a new multibranched compound, bis(5-[4-{N,N-di(4-[4-{5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl}styryl]phenyl)amino}styryl]thien-2-yl)ethenylene. Linear absorption spectra and luminescence spectra of the component and the multibranched chromophores revealed a hypochromic effect for the multibranched dye. A very effective energy transfer from the excited arm units to the π-conjugated bridging unit is observed. The two-photon cross-sections were measured using the femtosecond Z-scan techni...