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首页> 外文期刊>Chemistry: A European journal >Frozen Dissymmetric Cavities in Resorcinarene-Based Coordination Capsules
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Frozen Dissymmetric Cavities in Resorcinarene-Based Coordination Capsules

机译：基于间苯二酚的配位胶囊中的冷冻不对称腔

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摘要

By introducing slight structural modifications to a D-4-symmetric coordination capsule, we succeeded in isolating the nearly enantiopure capsules (P)- and (M)-2a(BF4)(4). Chiral guest, dibenzyl 4,4-diacetoxy-6,6-dimethyl-[1,1-biphenyl]-2,2-dicarboxylate (3) was encapsulated within the dissymmetric cavity of 2a(BF4)(4), resulting in a high diastereoselectivity of >99% de. The encapsulated guest was successfully removed from the complex without racemization through precipitation of the empty capsule. CD spectra confirmed that the chirality of the capsule was maintained in THF and 1,4-dioxane for long periods, whereas a small amount of acetonitrile accelerated racemization of the empty capsule. The activation parameters of the racemization reaction were determined in dichloromethane and 1,2-dichloroethane, resulting in positive enthalpic contributions and large negative entropic contributions, respectively. Accordingly, the racemization fits a first-order kinetic model. Mechanically coupled Cu+-2,2-bipyridine coordination centers were responsible for the high-energy barrier of racemization and led to the unique chiral memory of the dissymmetric cavity, which was turned off by the addition of acetonitrile.
机译：通过对D-4-对称配位胶囊进行轻微的结构修饰，我们成功分离出几乎对映纯的胶囊（P）-和（M）-2a（BF4）（4）。手性客体2,4,4-二乙酰氧基-6,6-二苄基-[1,1-联苯] -2,2-二羧酸二苄酯（3）封装在2a（BF4）（4）的不对称腔内， > 99％de的高非对映选择性通过空胶囊的沉淀，被包封的客人被成功地从复合物中除去而没有消旋。 CD光谱证实，该胶囊的手性在THF和1，4-二恶烷中保持了很长一段时间，而少量的乙腈促进了空胶囊的消旋。在二氯甲烷和1,2-二氯乙烷中测定外消旋反应的活化参数，分别导致正焓贡献和大的负熵贡献。因此，外消旋拟合一阶动力学模型。机械耦合的Cu + -2,2-联吡啶配位中心负责外消旋作用的高能垒，并导致不对称空腔的独特手性记忆，这种记忆通过添加乙腈而关闭。

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