解锁 n-alk-1-ynes 构象异构体：量子“扳机指”与“僵硬关节”构象
Unlocking n-alk-1-ynes Conformers: Quantum "Trigger Finger" versus "Stiff Joint" Conformations
AI总结：
本研究通过量子化学分析揭示了 n-alk-1-ynes 炔端存在平面与倾斜两种近乎等能的构象，阐明了其独特的量子“扳机指”动力学特征，为分子电子学中的光谱数据解释与构象控制提供了新蓝图。
摘要：
n-alk-1-ynes (CnA) 的分子构象传统上被简化为全平面结构。我们报告了一项全面的量子化学分析，揭示了在炔端存在两个近乎等能的旋转异构体：平面（C$_s$）和倾斜（C$_1$）。高且对称的旋转能垒（$\approx 150$\,meV）源于 $\mathrm{sp}$ 中心附近独特的空间位阻缓解，以及 C$_1$ 的电子稳定作用。这创造了一种独特的动力学特征：量子“扳机指”（$α$ 旋转）强制形成 $\approx 50\%:\,50\%$ 的 $\mathrm{C}_s/\mathrm{C}_1$ 系综，与烷基链的热力学偏向的“僵硬关节”（$δ$ 旋转）形成鲜明对比。这种结构简并性要求在光谱数据解释中进行系综平均，而缓慢的相互转化允许在合成和分子结制造过程中进行动力学捕获和有意的构象异构体富集。我们的工作重新定义了炔烃锚，为准确解释光谱数据和在分子电子学中实现构象控制提供了蓝图。
英文摘要：
Molecular conformation in n-alk-1-ynes (CnA) is conventionally simplified to an all-planar structure. We report a comprehensive quantum chemical analysis revealing two near-isoenergetic rotamers at the acetylenic terminus: planar (C$_s$) and skewed (C$_1$). The high, symmetric rotational energy barrier ($\approx 150$\,meV) arises from unique steric relief near the $\mathrm{sp}$ center coupled with electronic stabilization of C$_1$. This creates a unique kinetic profile: a Quantum ``Trigger Finger'' ($α$ rotation) that enforces an $\approx 50\%:\,50\%$ $\mathrm{C}_s/\mathrm{C}_1$ ensemble, sharply contrasting with the thermodynamically biased ``Stiff Joint'' ($δ$ rotation) of the alkyl chain. This structural degeneracy necessitates ensemble averaging for spectroscopic data interpretation, while the slow interconversion permits kinetic trapping and intentional conformer enrichment during synthesis and molecular junction fabrication. Our work redefines the alkyne anchor, providing a blueprint for accurate interpretation of spectroscopic data and achieving conformational control in molecular electronics.
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