Abstract: Two-photon absorption (TPA) properties of multibranch chromophores with nitrogen coupling center, N-[4-{2-(3,5-di-{5-[4-(tert-butyl)phenyl]-1,3,4-oxadiazol-2-yl}phenyl)-1-ethenyl}phenyl]-N,N-diphenylamine (BPODPA), N,N-bis[4-{2(3,5-di-{5-[4-(tert-butyl)phenyl]-1,3,4-oxadiazol-2-yl}phenyl)-1-ethenyl}phenyl]-N-phenylamine (BBPOPA) and N,N,N-tris[4-{2-(3,5-di-{5-[4-(tert-butyl)phenyl]-1,3,4-oxadiazol-2-yl}phenyl)-1-ethenyl}phenyl] amine (TBPOA), were measured by nonlinear transmission method. Single photon excited fluorescence and two-photon excited fluorescence (TPEF) of the chromophores were studied. The effect of dendronization on the TPA and TPEF characters of triphenylamine-based chromophores was investigated. When pumped with 800 nm laser irradiation, chromophores BPODPA, BBPOPA, and TBPOA showed strong two-photon excited blue green fluorescence at 502, 515, and 518 nm, respectively. These multibranched chromophores showed large TPA cross-section. The enhanced two-photon absorption found in these chromophores was attributed to the fact that the multibranched chromophores had both an extended π-conjugated system and an increased intramolecular cooperative effect compared to the one-branched chromophore.

Key words: Multibranch chromophore, Two-photon absorption, Two-photon excited fluorescence, Frequency upconversion