通过单分子力光谱了解梯形环丁烷机械团的机械化学,Journal of the American Chemical Society

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通过单分子力光谱了解梯形环丁烷机械团的机械化学
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2021-07-26 , DOI: 10.1021/jacs.1c05857
Matías Horst ₁ , Jinghui Yang ₁ , Jan Meisner ₁ , Tatiana B Kouznetsova ₂ , Todd J Martínez _{1,

3} , Stephen L Craig ₂ , Yan Xia ₁

Affiliation

我们最近报道了一系列梯型环丁烷机械载体，其聚合物可以从非共轭结构转变为共轭结构，并同时改变许多性质。这些多环mechanophores，即外-ladderane /烯，内-benzoladderene和外-bicyclohexene-周边-萘，与第一个环丁烷稠合的环结构不同，开环自由能变化显着不同，立体化学不同。为了更好地了解它们的机械化学，我们使用单分子力谱 (SMFS) 来表征它们的力-延伸行为并测量阈值力。阈值力与第一个键的活化能相关，但与聚合物主链远端稠环的应变无关，这表明这些梯型机械团的活化发生在类似的早期过渡态下，这得到了支持力修正势能面计算。我们进一步确定了机械生成的二烯的立体化学，并通过实验和计算观察到了这些机械团的显着且可变的轮廓长度伸长率。对梯形机械团的基本理解将有助于未来设计具有放大力响应的多循环机械团及其作为机械响应材料的应用。

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Understanding the Mechanochemistry of Ladder-Type Cyclobutane Mechanophores by Single Molecule Force Spectroscopy

We have recently reported a series of ladder-type cyclobutane mechanophores, polymers of which can transform from nonconjugated structures to conjugated structures and change many properties at once. These multicyclic mechanophores, namely, exo-ladderane/ene, endo-benzoladderene, and exo-bicyclohexene-peri-naphthalene, have different ring structures fused to the first cyclobutane, significantly different free energy changes for ring-opening, and different stereochemistry. To better understand their mechanochemistry, we used single molecule force spectroscopy (SMFS) to characterize their force–extension behavior and measure the threshold forces. The threshold forces correlate with the activation energy of the first bond, but not with the strain of the fused rings distal to the polymer main chain, suggesting that the activation of these ladder-type mechanophores occurs with similar early transition states, which is supported by force-modified potential energy surface calculations. We further determined the stereochemistry of the mechanically generated dienes and observed significant and variable contour length elongation for these mechanophores both experimentally and computationally. The fundamental understanding of ladder-type mechanophores will facilitate future design of multicyclic mechanophores with amplified force-response and their applications as mechanically responsive materials.

更新日期：2021-08-11

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