A cyclophane-based host-guest charge transfer complex for NIR-II photothermal conversion

Structurally well-defined small organic photothermal agents (PTAs) in the NIR-II biowindow (1000-1700 nm) have garnered considerable attention, but their rarity greatly limits their wide applications. Herein, we report a host-guest charge-transfer (CT) complex, TTF?TBox-12+, constructed by electron-deficient naphthalene diimide (NDI) cyclophane TBox-12+ and electron-rich guest tetrathiafulvalene (TTF) in 1 : 1 host/guest stoichiometry. Owing to strong CT absorption, TTF?TBox-12+ showed high NIR-II photothermal conversion efficiency in both aqueous solution and the solid state, and then was exploited as a high-performance PTA for antibacterial applications and seawater desalination. This work provides an insight for the development of new structurally well-defined NIR-II PTAs via host-guest CT interaction.