Influence of Internal Molecular Motions in the Photothermal Conversion Effect of Charge-Transfer Cocrystals

Herein, we report two new charge-transfer organic cocrystals, CP-TCNQ and CP-TFBQ. The two cocrystals exhibit broad absorption, good thermal stability, and low photoluminescence quantum yields, the necessary requirements to show the photothermal conversion (PTC) effect. Indeed, the two cocrystals exhibit distinct PTC efficiencies of 11.0 ± 1.4% (CP-TCNQ) and 17.0 ± 1.0% (CP-TFBQ). The 55% improvement in the observed efficiencies is attributed to the fast in-plane reorientations of the TFBQ fragment, as determined by detailed ssNMR spectroscopy and DFT calculations. This work provides for the first time experimental and computational evidence that the molecular motion of a cocrystal coformer increases its PTC efficiency, paving the way to the design of new crystalline materials with PTC as a regulated property.本文报道了两种新型电荷转移有机共晶：CP-TCNQ与CP-TFBQ。这两种共晶具备宽光谱吸收、优异的热稳定性以及较低的光致发光量子产率，均为实现光热转换（photothermal conversion, PTC）效应的必要条件。实验证实，二者分别展现出11.0 ± 1.4%（CP-TCNQ）与17.0 ± 1.0%（CP-TFBQ）的显著光热转换效率。观测到的效率提升达55%，可归因于TFBQ片段快速的面内重取向，该结论通过详尽的固体核磁共振（solid-state nuclear magnetic resonance, ssNMR）谱学表征与密度泛函理论（density functional theory, DFT）计算得以验证。本研究首次提供了实验与计算双重证据，证明共晶组分的分子运动可提升其光热转换效率，为以光热转换为可调控属性的新型晶态材料设计开辟了全新路径。