Red-light-excited dynamic near-infrared organic afterglow materials for in vivo bioimaging.

Extending the excitation and emission wavelengths into the red or even near-infrared region is a highly challenging yet scientifically valuable research topic in the field of organic afterglow materials. To solve this issue, we put forward a twisted intramolecular charge transfer dopant molecule design strategy, in which long-lived electron-deficient dopant is decorated with electron-rich substituent. In this way, the orbital energy level of the dopant can be lowered while maintaining the compatibility with the host. Benefiting from the twisted molecular conformation and small energy gap, the obtained dopant (CN) shows visible-light-excited afterglow with various performance (decay path, lifetime, emission wavelength) when doped into different matrices. Particularly, the maximum excitation wavelength extends to 567 nm and tails to 700 nm when CN is doped into benzophenone matrix. More importantly, the maximum emission wavelength of the afterglow extends to 725 nm (τ = 67.82 ms). We also successfully apply this material in autofluorescence-free bioimaging. This work provides a viable molecular design strategy for developing red-light-excitable near-infrared afterglow materials and demonstrates their potential for in vivo bioimaging.