Abstract
AbstractA 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 cm4 s photon–1 molecule–1) that are suitable for biological applications in live specimens. The propeller π‐conjugated systems of 3 (a C3 analogue of 1) shows threefold enhancement for the two‐photon absorption cross‐section (650 cm4 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 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.
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