Crystal Fluidity Reflected by Fast Rotational Motion at the Core, Branches, and Peripheral Aromatic Groups of a Dendrimeric Molecular Rotor.
Crystal Fluidity Reflected by Fast Rotational Motion at the Core, Branches, and Peripheral Aromatic Groups of a Dendrimeric Molecular Rotor.
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晶体流动性由树突中元分子转子的核心，分支和周围芳族组的快速旋转运动反映。
DOI：
10.1021/jacs.6b01398
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发表时间：
2016-04-06
影响因子：
15
通讯作者：
Garcia-Garibay MA
中科院分区：
文献类型：
--
作者：
Jiang X;O'Brien ZJ;Yang S;Lai LH;Buenaflor J;Tan C;Khan S;Houk KN;Garcia-Garibay MA
低堆积密度是由静态和移动组件构建的两性晶体的关键结构特征。在这里，我们报道了一种松散堆积的树枝状转子晶体，2，及其所有芳香族基团的快速动力学，这两者都是由分子的超支化结构产生的。化合物 2 采用收敛策略合成，构建中心亚苯基核心，其定子由两层三芳基甲基组成。单晶 X 射线衍射分析证实了一种低密度堆积结构，每个晶胞由 1 个分子、2 个和大约 8 个溶剂分子组成。合成了 2 的三种同位素异体物，利用变温四极回波 2 H NMR 光谱研究固态分子中每个片段的运动。光谱的线形分析表明，在环境温度下，中心亚苯基、六个分支亚苯基和十八个外围苯基都在晶体中表现出兆赫兹旋转动力学。阿伦尼乌斯对数据的分析给出了结构不同部分的相似活化能和指前因子。观察到的指前因子比基本位点交换过程的指数前因子大 4-6 个数量级，表明动力学并非由静态能量势决定。相反，2 晶体中旋转的活化能由温度相关的局部结构波动和晶体流动性控制。
Low packing densities are key structural features of amphidynamic crystals built with static and mobile components. Here we report a loosely packed crystal of dendrimeric rotor, 2, and the fast dynamics of all its aromatic groups, both resulting from the hyperbranched structure of the molecule. Compound 2 was synthesized with a convergent strategy to construct a central phenylene core with stators consisting of two layers of triarylmethyl groups. Single crystal X-ray diffraction analysis confirmed a low-density packing structure consisting of one molecule of 2 and approximately eight solvent molecules per unit cell. Three isotopologues of 2 were synthesized to study the motion of each segment in the molecule in the solid state using variable temperature quadrupolar echo 2H NMR spectroscopy. Line shape analysis of the spectra reveals that the central phenylene, the six branch phenylenes and the eighteen periphery phenyls all display megahertz rotational dynamics in the crystals at ambient temperature. Arrhenius analysis of the data gives similar activation energies and pre-exponential factors for different parts of the structure. The observed pre-exponential factors are 4–6 orders of magnitude greater than those of elementary site-exchange processes, indicating that the dynamics are not dictated by static energetic potentials. Instead, the activation energies for rotations in the crystals of 2 are controlled by temperature dependent local structural fluctuations and crystal fluidity.
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DOI：
10.1073/pnas.0502816102
发表时间：
2005-08-02
影响因子：
11.1
作者：
Garcia-Garibay, MA
通讯作者：
Garcia-Garibay, MA
影响因子：
38.3
作者：
Cheng, Chuyang;McGonigal, Paul R.;Stoddart, J. Fraser
通讯作者：
Stoddart, J. Fraser
影响因子：
16.6
作者：
De, Soumen;Pramanik, Susnata;Schmittel, Michael
通讯作者：
Schmittel, Michael
影响因子：
41.2
作者：
Akutagawa, Tomoyuki;Koshinaka, Hiroyuki;Nakamura, Takayoshi
通讯作者：
Nakamura, Takayoshi
影响因子：
--
作者：
BONDI, A
通讯作者：
BONDI, A