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首页> 外文期刊>Acta crystallographica. Section C, Structural chemistry. >Ethyl 4-(9H-carbazol-9-yl)benzoate: fivefold superstructure with ten crystallographically independent molecules refined from a twinned crystal
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Ethyl 4-(9H-carbazol-9-yl)benzoate: fivefold superstructure with ten crystallographically independent molecules refined from a twinned crystal

机译：4-（9H-咔唑-9-基）苯甲酸酯：五折叠结构，具有10个晶状体的晶体独立分子改进

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The photophysical properties of organic fluorophores are sensitive to the local sterics of the surrounding environment. Restriction of torsional motion in aggregates and crystals can give rise to enhanced emissive behavior. N-Aryl-substituted carbazoles serve an essential role as ubiquitous host matrices for organic light-emitting diodes, due to their large band gaps and high triplet energies, and so studies connecting photophysical behaviors with detailed crystallographic structural information are important. To elucidate the structural changes involved in the excited-state charge-transfer processes of N-aryl-substituted carbazoles with ester withdrawing groups, ethyl 4-(9H-carbazol-9-yl) benzoate, C_21H_17NO_2, was synthesized. The compound crystallizes with ten independent molecules in the asymmetric unit that pack together through moderate C—H ??? -π interactions between carbazole units (2.5-2.9 A) and π-stacks of benzoate groups (3.8-3.9 A) between neighboring molecules. Four of the ten independent molecules show disorder by rotation of the ethyl carboxylate groups, with major occupancy rates between 0.931 (3) and 0.840 (3). The attached benzoate groups are also disordered, with identical occupancies, to compensate for the altered steric profile of the misaligned ethyl ester groups. For two molecules, the disorder extends to the entire carbazole units as well. Torsion angles between the nonplanar carbazole and benzoate groups range from θ = 44.8 to 57.2°, while those between the benzoate planes and the carboxylate COO atoms vary from α = 6.4 to 15.7°. The crystal is twinned by pseudomerohedry. The superstructure can be reduced to a hypothetical averaged parent structure in the space group Pbcn with Z' = 1, displaying fourfold disorder. Variable-temperature data collection shows that there is no phase transition between the disordered supercell and the hypothetical parent structure; supercell reflections persist up to 350 K. We propose that the disorder and variation in torsion angles result from frustrated close-packing and necessitate a unit cell with a high Z' number.
机译：有机荧光团的光物理性质对周围环境的本地静态感性敏感。在聚集体和晶体中的扭转运动的限制会产生增强的发射行为。 N-芳基取代的咔唑用于有机发光二极管的普遍存在宿主基质的基本作用，由于它们的大带间隙和高三重子能量，因此与详细的晶体结构信息连接光性行为的研究很重要。为了阐明与酯抽出基团的N-芳基取代的咔唑的兴奋状态电荷转移方法中所涉及的结构变化，合成4-（9h-咔唑-9-基）苯甲酸苯甲酸苯甲酸酯，C_21H_17NO_2。该化合物用在不对称单元中用十个独立分子结晶，通过中等C-H包装在一起??? - 咔唑单元（2.5-2.9A）与相邻分子之间的苯甲酸酯基团（3.8-3.9A）之间的相互作用。十个独立分子中的四种通过乙基羧酸乙酯基团的旋转显示疾病，主要占用率在0.931（3）和0.840（3）之间。连接的苯甲酸酯基团也具有相同的占用，以补偿未对准的乙酯基的改变的空间谱。对于两个分子，该病症也延伸到整个咔唑单元。非平面咔唑和苯甲酸酯基之间的扭转角度从θ= 44.8至57.2°之间，而苯甲酸架和羧酸酯官官能之间的扭转角度在α= 6.4至15.7°之间变化。 Crysty由Pseudomerohedry孪生。上部结构可以减少到具有Z'= 1的空间组PBCN中的假设平均母体结构，显示为四倍障碍。可变温度数据收集表明，无序的超级电池与假想父母结构之间没有相位过渡; SuperCell反射持续到350 K.我们提出了扭转角度的紊乱和扭转角度的变化，从而使得具有高Z'数的单位单元。

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