[2.2]パラシクロファンの剛直性を利用したヒンジ型超分子メカノフォア～力の変化をシャープに可視化～

2025-07-18 東京科学大学

図1．[2.2]パラシクロファンを利用したヒンジ型超分子メカノフォアの分子骨格

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• https://onlinelibrary.wiley.com/doi/10.1002/anie.202510114

[2.2]パラシクロファンをベースとしたヒンジ型メカノクロミックメカノフォア Hinge-Like Mechanochromic Mechanophores Based on [2.2]Paracyclophane

Shohei Shimizu, Dr. Jess M. Clough, Prof. Christoph Weder, Prof. Yoshimitsu Sagara
Angewandte Chemie International Edition Published: 30 June 2025
DOI:https://doi.org/10.1002/anie.202510114

Graphical Abstract

Hinge-like supramolecular mechanophores utilizing [2.2]paracyclophane have been developed. In the force-free state, the rigid [2.2]paracyclophane forces two luminophores into proximity, leading to excimer-dominant photoluminescence. Stretching the polyurethane films into which the mechanophores are covalently incorporated results in the structures of the mechanophores changing to more open forms, which leads to monomer-dominant emission being observed.

Abstract

A hinge-like supramolecular mechanophore based on a [2.2]paracyclophane core and two excimer-forming 1,6-bis(phenylethynyl)pyrene luminophores is presented. Each luminophore shares one phenyl group with the [2.2]paracyclophane, resulting in a rigid and strained structure that forces the two luminophores into close proximity. As a consequence, the photoluminescence of the mechanophore in THF solution and in solid films of a polyurethane containing the new motif is dominated by excimer emission. Stretching the polymer films causes an easily discernible change from bright yellow excimer to blue–green monomer-dominated emission. The ratio of excimer to monomer emission intensities traces the nonlinear stress–strain curves of the polymer well and is a good indicator for the macroscopically applied force. The reversibility of the mechanoresponse, theoretical analyses, and reference experiments with a similar mechanophore in which the emitters and the [2.2]paracyclophane core are connected by flexible linkers support the conclusion that the mechanoactivation is caused by distorting the molecule into a bent, more open conformation and not the scission of covalent bonds. The operating principle was further confirmed by investigating a second hinge-like mechanophore based on a [2.2]paracyclophane core and 1,4-bis(phenylethynyl)benzene emitters.