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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >Three conformational polymorphs and order-disorder phase transition in a calix[4]arene bis(crown)
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Three conformational polymorphs and order-disorder phase transition in a calix[4]arene bis(crown)

机译：杯[4]芳烃双（冠）中的三种构象多晶型与有序无序相变

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摘要

Three polymorphs of a calix[4]arene fixed in the 1,3-alternate conformation by two bridges, a crown-6 on one side and a crown-6 including a photoisomerizable azobenzene unit on the other, 8,11,14,28,31,34,37,40,43,57,60,63-dodecaoxa-2,3-diazanonacyclo[62.2.2.2(4 ,7).1(16,45).1(26,55).0(15,22),0(22,27).0(44.49).0(51,56)] (66),2,4,6,15,17,19,22,24,26,44,46,48,51,53,55,64,67,69-nonadecene, have been characterized by single-crystal X-ray diffraction. In all the polymorphs the azobenzene group is in the more stable trans conformation. The polymorphism arises from the high conformational flexibility of the bridges, which are arranged differently and are highly disordered in the two monoclinic forms (1) and (2a). Form (2a) presents a phase transition near 268 (2) K, leading to a triclinic form (2b), differing from the high-temperature form by some ordering of the chains and a subsequent reduction in crystallographic site multiplicity. The evolution of the cell parameters and peak width with temperature has been investigated down to 173 (2) K. Adiabatic calorimetry measurements indicate a smooth transition centered at 265.0 (1) K, with a heat capacity jump of 60 mJ g(-1) K-1, suggesting a second-order nature for the transition. [References: 27]
机译：杯[4]芳烃的三个多晶型物通过两个桥固定在1,3-交替构象上，一侧为冠6，另一侧为冠6，其上包括可光异构的偶氮苯单元，8,11,14,28 ，31,34,37,40,43,57,60,63-dodecaoxa-2,3-diazanonacyclocyclo [62.2.2.2（4，7）.1（16,45）.1（26,55）.0（ 15,22），0（22,27）.0（44.49）.0（51,56）]（66），2,4,6,15,17,19,22,24,26,44,46， 48，51，53，55，64，67，69-十八碳烯，已经通过单晶X射线衍射表征。在所有的多晶型物中，偶氮苯基处于更稳定的反式构象。多态性是由桥的高构象柔性引起的，桥的构型不同，并且在两种单斜晶型（1）和（2a）中高度无序。晶型（2a）在268（2）K附近出现相变，从而形成三斜晶型（2b），其与高温晶型的区别在于链的某种顺序并随后降低了晶体学位点的多重性。在低至173（2）K的条件下研究了细胞参数和峰宽随温度的变化。绝热量热法测量表明，以265.0（1）K为中心的平稳过渡，热容跃迁为60 mJ g（-1） K-1，表明过渡的二阶性质。 [参考：27]

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