Metal‐Free Catalytic Formation of a Donor‐Acceptor‐Donor Molecule and Its Lewis Acid‐Adduct Singlet Diradical with High‐Efficient NIR‐II Photothermal Conversion

Abstract

AbstractWe have synthesized a quinone‐incorporated bistriarylamine donor‐acceptor‐donor (D–A–D) semiconductor 1 by B(C6F5)3 (BCF) catalyzed C−H/C−H cross coupling via radical ion pair intermediates. Coordination of Lewis acids BCF and Al(ORF)3 (RF=C(CF3)3) to the semiconductor 1 afforded diradical zwitterions 2 and 3 by integer electron transfer. Upon binding to Lewis acids, the LUMO energy of 1 is significantly lowered and the band gap of the semiconductor is significantly narrowed from 1.93 eV (1) to 1.01 eV (2) and 1.06 eV (3). 2 and 3 are rare near‐infrared (NIR) diradical dyes with broad absorption both centered around 1500 nm. By introducing a photo BCF generator, 2 can be generated by light‐dependent control. Furthermore, the integer electron transfer process can also be reversibly regulated via the addition of CH3CN. In addition, the temperature of 2 sharply increased and reached as high as 110 °C in 10 s upon the irradiation of near‐infrared‐II (NIR‐II) laser (1064 nm, 0.7 W cm−2), exhibiting a fast response to laser. It displays excellent photothermal stability with a photothermal (PT) conversion efficiency of 62.26 % and high‐quality PT imaging.