Department of Materials Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552, Japan.
JST-PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
J Am Chem Soc. 2021 Apr 14;143(14):5519-5525. doi: 10.1021/jacs.1c01328. Epub 2021 Mar 30.
A new approach to cyclophane-based supramolecular mechanophores is presented. We report a mechanically responsive cyclic motif that contains two fluorescent 1,6-bis(phenylethynyl)pyrene moieties that are capable of forming intramolecular excimers. The emission spectra of dilute solutions of this cyclophane and a polyurethane elastomer into which a small amount of the mechanophore (0.08 wt %) had been covalently integrated are dominated by excimer emission. Films of the cyclophane-containing polyurethane also display a considerable portion of excimer emission, but upon deformation, the fluorescence becomes monomer-dominated and a perceptible change from cyan to blue is observed. The response is instant, reversible, and consistent with a mechanically induced change of the molecular conformation of the mechanophore so that the excimer-promoting interactions between the luminophores are suppressed. In-depth investigations show a correlation between the applied strain and the emission color, which can conveniently be expressed by the ratio of monomer to excimer emission intensity. The current study suggests that cyclophanes can be utilized to develop various supramolecular mechanophores that detect and visualize weak forces occurring in polymeric materials or generated by living tissues.
提出了一种基于环芳烷的超分子机械发色团的新方法。我们报道了一种机械响应的环状基序，它包含两个荧光 1,6-双（苯乙炔基）芘部分，能够形成分子内激基缔合物。这种环芳烷和少量机械发色团（0.08wt%）共价结合的聚氨酯弹性体的稀溶液的发射光谱主要由激基缔合物发射主导。含环芳烷的聚氨酯薄膜也显示出相当一部分的激基缔合物发射，但在变形时，荧光变为单体主导，观察到从青色到蓝色的明显变化。这种响应是瞬间、可逆的，与机械诱导的机械发色团分子构象变化一致，从而抑制了发光体之间促进激基缔合物形成的相互作用。深入的研究表明，施加的应变与发射颜色之间存在相关性，这可以通过单体与激基缔合物发射强度的比值方便地表示。本研究表明，环芳烷可用于开发各种超分子机械发色团，用于检测和可视化发生在聚合物材料或活体组织中的弱力。
