Throwing in a Monkey Wrench to Test and Determine Geared Motion in the Dynamics of a Crystalline 1D-Columnar Rotor Array,Journal of the American Chemical Society

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Throwing in a Monkey Wrench to Test and Determine Geared Motion in the Dynamics of a Crystalline 1D-Columnar Rotor Array
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2019-01-08 , DOI: 10.1021/jacs.8b11385
Salvador Pérez-Estrada _{1,

2} , Braulio Rodríguez-Molina _{1,

3} , Emily F. Maverick ₁ , Saeed I. Khan ₁ , Miguel A. Garcia-Garibay ₁

Affiliation

Crystals of molecular rotor 1 with a central 1,4-phenylene rotator linked to two molecules of the steroid mestranol were prepared with 1%, 5%, 20%, and up to 40% of the analogous 2, which contains a larger 2,3-difluorophenylene rotator and effectively acts as a monkey wrench that affects the rotation of the host. The packing motif of the desired P32 crystal form consists of 1D columns of nested rotors arranged in helical arrays with the central aromatic rotators disordered over two sites related by 85° rotation about their 1,4-axes. Rotational dynamics measured by quadrupolar echo 2H NMR line shape analysis were analyzed in terms of a process model that involves degenerate 180° jumps in the fast exchange regime combined with a highly correlated and entropically demanding jump of 85° between the two dynamically disordered sites. While the enthalpic and entropic barriers for the 180° jump estimated from 2H T1 measurements were Δ H⧧ = 2.7 ± 0.1 kcal mol-1 and Δ S⧧ = -5.0 ± 0.5 cal mol-1 K-1, respectively, the corresponding parameters for the slower 85° jumps, determined by line shape analysis, were Δ H⧧ = 2.2 kcal mol-1 and Δ S⧧ = -23 cal mol-1 K-1. Increasing amounts of the larger molecular rotor 2 in the solid solution results in significant dynamic perturbations as the guest, acting as a monkey wrench, reaches values of one out of every five molecular rotors in the chain.

中文翻译：

用扳手来测试和确定晶体一维柱状转子阵列动力学中的齿轮运动

用 1%、5%、20% 和高达 40% 的类似物 2 制备分子转子 1 的晶体，其中心 1,4-亚苯基转子与两个类固醇美雌醇分子相连，其中含有更大的 2， 3-二氟亚苯基旋转器，有效地充当影响主机旋转的活动扳手。所需的 P32 晶型的填充图案由一维嵌套转子列组成，这些转子排列成螺旋形阵列，中心芳香族转子在两个位点上无序排列，两个位点围绕它们的 1,4 轴旋转 85°。根据过程模型分析了通过四极回波 2H NMR 线形分析测量的旋转动力学，该模型涉及快速交换机制中的简并 180°跳跃，结合两个动态无序位点之间高度相关且熵要求的 85°跳跃。虽然根据 2H T1 测量估计的 180°跳跃的焓和熵障碍分别为 Δ H⧧ = 2.7 ± 0.1 kcal mol-1 和 Δ S⧧ = -5.0 ± 0.5 cal mol-1 K-1，但相应的参数对于较慢的 85° 跳跃，通过线形分析确定，Δ H⧧ = 2.2 kcal mol-1 和 Δ S⧧ = -23 cal mol-1 K-1。在固溶体中增加较大分子转子 2 的量会导致显着的动态扰动，因为充当活动扳手的客体达到链中每五个分子转子中的一个的值。

更新日期：2019-01-08

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