Sulfone/Carbonyl‐Based Donor‐Acceptor Fluorescent Dyes: Synthesis, Structures, Photophysical Properties and Cell Imaging

Abstract

AbstractElectron‐accepting units play vital roles in constructing donor‐acceptor (D‐A) conjugated organic optoelectronic materials; the electronic structures and functions of the acceptors need to be carefully unveiled to controllably tailor the optoelectronic properties. We have synthesized two D‐A conjugated organic fluorophores, TPA‐SO and TPA‐CO, with similar molecular skeletons based on sulfone‐ or carbonyl‐containing polycyclic aromatic acceptors. Both TPA‐SO and TPA‐CO display obvious solvent polarity‐dependent photophysical properties and large Stokes shift of over 100 nm for strong intramolecular charge transfer processes. Experimental evidence indicates that the sulfone group in TPA‐SO merely serves as a strong electron‐withdrawing unit. TPA‐SO shows yellowish‐green emission with a peak at 542 nm and an absolute photoluminescence quantum yield (PLQY) of 98 % in solution, whereas the carbonyl group in TPA‐CO can act as both an electron‐withdrawing unit and spin transition convertor, so TPA‐CO displays red emission with a low absolute PLQY of 0.32 % in solution. Impressively, upon going from solution to aggregate state, TPA‐SO nanoparticles keep a high PLQY of 9.5 % and moderate biocompatibility, thus they are good nano‐agents for cellular fluorescence imaging. The results reveal that the inherent acceptor characteristic acts as a crucial effect in the photophysical properties and applications of the organic fluorophores.