Rational design of two-photon absorbing dicyanomethylene-4H-chromene derivatives and their application in bioimaging

In vitro and in vivo fluorescence imaging of cells and animals plays a significant role in studying biological systems. However, autofluorescence becomes a serious issue in vivo imaging under excitation at UV-vis wavelengths where biological molecules cause interference with the chromophore. In order to address this issue, a novel class of dicyanomethylene-4H-chromene (DCM) derivatives (PCM, PCV, BPCM and BPCV) that can be excited at similar to 900 nm under two-photon excitation conditions and emit in the red wavelength region (>= 600 nm) have been developed. Particularly, one of the DCM derivatives (PCM) shows several advantages, including remarkable two-photon absorption (2PA) properties in the near infrared (NIR) region, superior photostability, large Stokes-shift and pronounced solvent-sensitive emission behavior, which is favorable for in vivo fluorescence labelling with a high signal-to-noise ratio. (C) 2017 Elsevier Ltd. All rights reserved.