| Abstract
| - This paper presents a molecular design for a two-photon absorbing structure, whichcontains 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 triphenylaminederivative 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 anew 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 ahypochromic effect for the multibranched dye. A very effective energy transfer from theexcited arm units to the π-conjugated bridging unit is observed. The two-photon cross-sectionswere measured using the femtosecond Z-scan technique at several excitation wavelengthsin the 620−800 nm range. Comparing the nonlinear absorption coefficients observed for theconstituent chromophore dyes with that for the multibranched compound, we found thatthe arm units make the dominant contribution to the two-photon absorption when thewavelength of excitation is longer than 720 nm.
|
