Comparative studies of multi-photon induced emission by pyridine-based small molecular probes in biological media: Selective binding of bioactive molecules and in vitro imaging

Wanqing Wu, Hoi Kuan Kong, Hongguang Li, Yu Man Ho, Yuan Gao, Jianhua Hao, Margaret B. Murphy, Michael Hon Wah Lam, Ka Leung Wong, Chi Sing Lee

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3 Citations (Scopus)


A new class of organic molecular probes (1-3) based on a 1,3-disubstituted diethynylbenzene core has been developed. Both 1 and 2 (with the esters of 1 replaced by diethylamides in 2) show good linear and three-photon induced photophysical properties with two-photon absorption cross-sections (185-210 cm4sphoton-1molecule-1) that are suitable for biological applications in live specimens. The propeller π-conjugated systems of 3 (a C3analogue of 1) shows threefold enhancement for the two-photon absorption cross-section (650 cm4sphoton-1molecule-1). Solvatochromism was observed in the fluorescence spectra of all these molecular probes; in acidic medium (pH = 4-5) their fluorescence emissions are slightly blueshifted with a threefold enhancement in intensity relative to those observed under basic conditions (pH = 10-11). In the fluorometric titration study against a variety of bioactive small molecules, only 2 shows strong binding affinity (log KB> 7) towards citrates and bicarbonates with approximately 30 nm redshift. The in vitro emission spectra of 2 obtained show the same emission upon addition of anions to the solution. The results of these studies could provide new molecular-design strategies for two-photo absorption (TPA) chromophores and new materials for two/multi-photon imaging in vitro. A new class of organic molecular probes has been developed, and the cell-permeable properties were improved dramatically by introducing diethylamide moieties. Only 2 shows strong emission enhancement uponbinding with citrates and bicarbonates. The emission spectra of 2 obtained in vitro show the same emission with citrate and hydrogencarbonate.
Original languageEnglish
Pages (from-to)5054-5060
Number of pages7
JournalEuropean Journal of Organic Chemistry
Issue number26
Publication statusPublished - 1 Sep 2011


  • Anions
  • Fluorescent probes
  • Imaging agents
  • Luminescence
  • Photochemistry

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry

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