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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
Author(s) -
Wu Wanqing,
Kong HoiKuan,
Li Hongguang,
Ho YuMan,
Gao Yuan,
Hao Jianhua,
Murphy Margaret B.,
Lam Michael HonWah,
Wong KaLeung,
Lee ChiSing
Publication year - 2011
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201100570
Subject(s) - chemistry , solvatochromism , fluorescence , conjugated system , chromophore , molecule , absorption (acoustics) , photochemistry , molecular probe , two photon absorption , small molecule , emission spectrum , titration , spectral line , organic chemistry , polymer , materials science , dna , laser , biochemistry , physics , quantum mechanics , astronomy , optics , composite material
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 cm 4 s photon –1 molecule –1 ) that are suitable for biological applications in live specimens. The propeller π‐conjugated systems of 3 (a C 3 analogue of 1 ) shows threefold enhancement for the two‐photon absorption cross‐section (650 cm 4 s photon –1 molecule –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 K B > 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.