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Highly Efficient Multiphoton‐Absorbing Quadrupolar Oligomers for Frequency Upconversion
Author(s) -
Feng Xin Jiang,
Wu Po Lam,
Li King Fai,
Wong Man Shing,
Cheah Kok Wai
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201002227
Subject(s) - photon upconversion , materials science , optoelectronics , doping
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 ( σ 3 ) of up to 2.72×10 −77 cm 6 s 2 . 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.