Organic Near Infrared Photothermal Materials with Temperatures up to 450 oC Constructed by Cycloaddition-Retroelectrocyclization Click Reaction

Organic photothermal materials, especially those with near-infrared (NIR) absorbance and excellent photothermal properties, have attracted considerable attention for applications in energy conversion and biomedical therapy. In generally, synthesis of above organic photothermal materials require the use of high temperature, expensive noble metal catalysts, or UV lamp radiation. Herein, a facile [2+2] cycloaddition-cycloreversion ([2+2] CA-CR) reaction is employed for the efficient synthesis of nonplanar molecule (2ATPE-2F4) containing triphenylamine (TPA) and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) under ambient conditions by taking advantage of its click feature, atom-economic, unity yield, and simple purified procedure, etc. The resultant product exhibits exceptional properties including broad absorption edge over 1000 nm, and substantial radical characters with paramagnetic behavior, etc. Excitingly, it exhibits excellent photothermal properties and the temperature could be swiftly increased to as high as 450 °C in solid powder upon photo-irradiation. Thanks to the excellent photothermal properties, 2ATPE-2F4 was used for the construction of high temperature (> 200 oC) shape memory actuators triggered with NIR light. In addition, upon assembling the 2ATPE-2F4 into nanoparticle (2ATPE-2F4 NPs), it displayed good biocompatibility, excellent photothermal stability, and high photothermal conversion efficiency (PCE), enable it to be used to realize high-efficiency photothermal therapy. This work demonstrates the excellent potential of [2+2] CA-CR reactions for the synthesis of high-performance organic NIR photothermal materials.