CHIN-HUNG LAI2026-10-162026-10-162006-09-04Pure ID: 15433144Pure UUID: cca2bf68-8bd0-4e2d-af9a-756946580f3b10.1016/j.tet.2006.06.085https://www.scopus.com/pages/publications/33746297476https://scholars.csmu.edu.tw/handle/123456789/27194Sonogashira coupling between 3,5,3′,5′-tetrabromo-[2,2′]bithiophene and various terminal alkynes provides two-photon absorption (TPA) chromophores 1-6, which possess electron donor (D) and/or acceptor (A) alkynyl substituents at 3(3′) and 5(5′) sites of the bithiophene core. The up-converted fluorescence emission excited at 800 nm (Ti:sapphire femtosecond laser, ∼100 fs pulses) was used to determine the two-photon absorption cross-sections (σ) of these compounds. The corresponding TPA cross-section (σ) values ranging from 132 to 1120 GM (10-50 cm4 s photon-1) can be fine-tuned by the substitutents. The quadrupolar-type (A-π-D-π-A) chromophore 5 exhibits the largest σ value (1120 GM) in CH2Cl2 upon 800 nm excitation.7enjournal article