Ruffle-distorted meso-silylethynyl-substituted naphthoporphyrin showing near-infrared Q band beyond 800 nm

Abstract

Designing stable molecules with near-infrared (NIR) absorption and good light-to-heat conversion performance is important for phototherapy applications. Herein, we report the synthesis of copper-coordinated meso-tetrakis(triisopropylsilylethynyl)-tetranaphthoporphyrin 2-Cu by retro-Diels Alder reaction, which exhibited a Soret band at 534 nm and a NIR Q band at 818 nm. The single-crystal X-ray analysis of 2-Cu revealed a purely ruffle-distorted conformation with an S4 symmetry axis. Theoretical calculations show that 2-Cu has a narrower HOMO-LUMO gap than its meso-phenyl and meso-free analogs due to a decrease in LUMO energy level. The photothermal investigation of 2-Cu under 808 nm laser irradiation demonstrated its outstanding photostability and high photothermal conversion efficiency, indicating its promise as a photothermal therapeutic agent after functionalization.