McFadden Molly E, Osler Skylar K, Sun Yan, Robb Maxwell J
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States.
J Am Chem Soc. 2022 Dec 14;144(49):22391-22396. doi: 10.1021/jacs.2c08817. Epub 2022 Dec 2.
Multimodal mechanophores that exhibit complex mechanochromic behavior beyond the typical binary response are capable of distinguishing between multiple stress states through discrete changes in color. Naphthodipyran photoswitches contain two pyran rings fused to a central naphthalene core and represent a potentially promising framework for multimodal reactivity. However, the concurrent ring opening of both pyran moieties has previously proven inaccessible via photochemical activation. Here, we demonstrate that mechanical force supplied to naphthodipyran through covalently linked polymer chains generates the elusive dual ring-opened dimerocyanine product with unique near-infrared absorption properties. Trapping with boron trifluoride renders the merocyanine dyes thermally persistent and reveals apparent sequential ring-opening behavior that departs from the reactivity of previously studied mechanophores under the high strain rates imposed by ultrasound-induced solvodynamic chain extension.
具有超越典型二元响应的复杂机械变色行为的多模态机械力传感器能够通过颜色的离散变化区分多种应力状态。萘并二吡喃光开关包含两个与中心萘核稠合的吡喃环，是一种具有潜在前景的多模态反应性框架。然而，先前已证明通过光化学活化无法同时打开两个吡喃部分的环。在这里，我们证明通过共价连接的聚合物链提供给萘并二吡喃的机械力会产生难以捉摸的双环开环二聚体花菁产物，该产物具有独特的近红外吸收特性。用三氟化硼捕获使部花青染料具有热稳定性，并揭示了明显的顺序开环行为，这与先前研究的机械力传感器在超声诱导的溶剂动力学链延伸所施加的高应变率下的反应性不同。
