Synthesis, Structure, and Photothermal Conversion of a Bowl‐Shaped Nanographene Containing Fused 5‐/7‐Ring Pairs

Abstract

ABSTRACT Incorporation of non‐hexagonal topologies into bowl‐shaped nanographenes offers opportunities for tailoring their electronic properties and supramolecular behavior, however synthesis of such curved systems remains challenging. Herein, we report the facile synthesis of a bowl‐shaped nanographene ( TAT ) embedded with three circularly fused pentagon–heptagon (5/7) pairs via a three‐fold intramolecular Heck reaction. Its concave geometry is verified by nuclear magnetic resonance (NMR) spectroscopy, high resolution mass spectrometry, and x‐ray crystallography. Variable‐temperature 1 H NMR studies reveal a low bowl‐to‐bowl inversion barrier of 13.5 ± 1.3 kcal·mol −1 , enabling its fast dynamic motion even at room temperature. UV‐ vis absorption spectroscopy and cyclic voltammetry demonstrate a narrow energy gap, reflecting its highly delocalized π‐conjugation system. The concave geometry of TAT allows it to co‐assemble with fullerenes, forming a 2:1 complex with C 60 as confirmed by single‐crystal x‐ray diffraction analysis. Furthermore, femtosecond transient absorption spectroscopy reveals its ultrafast nonradiative excited‐state deactivation process. Benefiting from this photophysical behavior, water‐soluble nanoparticles of TAT encapsulated in an amphiphilic polymer achieve a high photothermal conversion efficiency of 41%. This work establishes a bottom‐up strategy for synthesizing an unprecedented bowl‐shaped nanographene and provides insights into its intrinsic optoelectronic, supramolecular properties, and photothermal conversion potentials.