Highly efficient multiphoton-absorbing quadrupolar oligomers for frequency upconversion

Xin Jiang Feng, Po Lam Wu, King Fai Li, Ricky M S WONG, Kok Wai CHEAH

Research output: Contribution to journalJournal articlepeer-review

26 Citations (Scopus)


Two series of quadrupolar diphenylamino-endcapped oligofluorenes, PhN-OF(n)-NPh (n=2-5) and PhN-OF(n)-TAZ-OF(n)-NPh (n=1-4), which have an electron-withdrawing 1,2,4-triazole (TAZ) moiety as central core, with D-π-A-π-D structural motif (D=donor, A=acceptor), have been synthesized by palladium-catalyzed Suzuki cross-coupling of 9,9-dibutyl-7-(diphenylamino)-2- fluorenylboronic acid and the corresponding (1,2,4-triazole-based) aryl halide as key step. On pumping with infrared femtosecond lasers, these oligomers showed very strong multiphoton-excited blue photoluminescence. These D-π-D and D-π-A-π-D quadrupolar oligofluorenes exhibit superior three-photon absorption properties compared to the respective D-π-A counterparts with a highest three-photon absorption cross-section (θ3) of up to 2.72 ×10-77 cm6s2. Despite the comparable linear and multiphoton absorption properties of the two types of quadrupolar oligomers PhN-OF(n)-NPh and PhN-OF(n)-TAZ-OF(n)-NPh, only the former exhibit remarkably intense and highly efficient multiphoton-excited frequency- upconverted deep blue lasing, which gives rise to record high lasing efficiency of 0.097% and very narrow of full width at half-maximum of the lasing spectra. Our findings suggest that quadrupolar-type molecules/oligomers are superior for multiphoton excited frequency upconverted lasing to their dipolar counterparts and also provide important guidelines to design highly efficient three-photon absorption molecules for photoluminescence and lasing applications.

Original languageEnglish
Pages (from-to)2518-2526
Number of pages9
JournalChemistry - A European Journal
Issue number8
Publication statusPublished - 18 Feb 2011

Scopus Subject Areas

  • Catalysis
  • Organic Chemistry

User-Defined Keywords

  • laser chemistry
  • multiphoton absorption
  • nonlinear optics
  • oligofluorenes
  • photoluminescence


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