Rational design of novel near-infrared fluorescent DCM derivatives and their application in bioimaging.

The development of innovative strategies for high-performance near-infrared (NIR) fluorescent materials is in urgent demand for bioimaging. By replacing the stronger electron-withdrawing groups or extending the π-conjugated system, novel NIR fluorescent materials of DCM analogues have been developed, along with several striking characteristics: bright NIR fluorescence over 700 nm, large Stokes shift and good photo-stability. It is demonstrated that introducing a stronger electron-withdrawing unit to the acceptor moiety of DCM analogues is a favourably efficient strategy to tune and prolong the emission wavelength into the NIR region with a large Stokes shift. In comparison with the commercial NIR dye ICG, S-DCM-N and S-DCM-P display excellent photostability and low photobleaching. The large Stokes Shift and NIR fluorescence channel of S-DCM-N and S-DCM-P are very favourable for fluorescence labelling with a high signal-to-noise ratio in living species.