Metal‐Free Catalytic Formation of a Donor‐Acceptor‐Donor Molecule and Its Lewis Acid‐Adduct Singlet Diradical with High‐Efficient NIR‐II Photothermal Conversion
Shanshan Kong, Li‐Ming Yang, Quanchun Sun, Tao Wang, Runbo Pei, Yue Zhao, Wenqing Wang, Yu Zhao, Haiyan Cui, Xinggui Gu, Xinping Wang
Abstract
Abstract We have synthesized a quinone‐incorporated bistriarylamine donor‐acceptor‐donor (D–A–D) semiconductor 1 by B(C 6 F 5 ) 3 (BCF) catalyzed C−H/C−H cross coupling via radical ion pair intermediates. Coordination of Lewis acids BCF and Al(OR F ) 3 (R F =C(CF 3 ) 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 CH 3 CN. 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.