We show herein that 1,10‐dicyano substitution restricts the paragon fluxionality of bullvalene to just 14 isomers which isomerize along a single cycle. The restricted fluxionality of 1,10‐dicyanobullvalene (DCB) is investigated by means of: (i) Bonding analyses of the isomer structures using the adaptive natural density partitioning (AdNDP). (ii) Quantum dynamical simulations of the isomerizations along the cyclic intrinsic reaction coordinate of the potential energy surface (PES). The PES possesses 14 equivalent potential wells supporting 14 isomers which are separated by 14 equivalent potential barriers supporting 14 transition states. Accordingly, at low temperatures, DCB appears as a hindered molecular rotor, without any delocalization of the wavefunction in the 14 potential wells, without any nuclear spin isomers, and with completely negligible tunneling. These results are compared and found to differ from those for molecular boron rotors. (iii) Born‐Oppenheimer molecular dynamics (BOMD) simulations of thermally activated isomerizations. (iv) Calculations of the rate constants in the frame of transition state theory (TST) with reasonable agreement achieved with the BOMD results. (v) Simulations of the equilibration dynamics using rate equations for the isomerizations with TST rate coefficients. Accordingly, in the long‐time limit, isomerizations of the 14 isomers, each with Cs symmetry, approach the “14 Cs → C7v” thermally averaged structure. This is a superposition of the 14 equally populated isomer structures with an overall C7v symmetry. By extrapolation, the results for DCB yield working hypotheses for so far un‐explored properties e.g. for the equilibration dynamics of C10H10.

中文翻译：

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通过取代限制分子流动性：1,10-二氰基丁瓦烯的案例研究

我们在此表明​​，1,10-二氰基取代将 Bullvalene 的典型流动性限制为仅 14 个异构体，这些异构体沿单个循环异构化。通过以下方式研究 1,10-二氰基牛瓦烯 (DCB) 的受限流动性：(i) 使用自适应自然密度分配 (AdNDP) 对异构体结构进行键合分析。 （ii）沿势能面（PES）的循环本征反应坐标异构化的量子动力学模拟。 PES 拥有 14 个等效势阱，支持 14 种异构体，这些异构体由支持 14 种过渡态的 14 个等效势垒隔开。因此，在低温下，DCB表现为受阻分子转子，14个势阱中波函数没有任何离域，没有任何核自旋异构体，并且隧道效应完全可以忽略不计。比较这些结果发现与分子硼转子的结果不同。 (iii) 热活化异构化的玻恩-奥本海默分子动力学 (BOMD) 模拟。 (iv) 在过渡态理论 (TST) 框架内计算速率常数，与 BOMD 结果取得合理的一致性。 (v) 使用具有 TST 速率系数的异构化速率方程模拟平衡动力学。因此，在很长的时间限制内，14种异构体的异构化，每个异构体都带有Cs对称性，接近“14 Cs→ C7v”热平均结构。这是 14 个同等分布的异构体结构的叠加，总体 C7v对称。通过外推，DCB 的结果得出了迄今为止尚未探索的特性的工作假设，例如 C 的平衡动力学10H10。