An electron-deficiency-based framework for NIR-II fluorescence probes.

Fluorescent probes in the NIR-II region provide high bioimaging quality. Optimizing the probe structure to achieve NIR-II imaging is ongoing, but remains challenging. Herein, increasing the electron withdrawing ability of the substituent in monochlorinated BODIPY greatly adjusted the emission wavelength from the NIR-I to NIR-II region, giving an efficient design strategy of NIR-II probes.