Goossens Karel, Lava Kathleen, Nockemann Peter, Van Hecke Kristof, Van Meervelt Luc, Driesen Kris, Görller-Walrand Christiane, Binnemans Koen, Cardinaels Thomas
Katholieke Universiteit Leuven, Department of Chemistry, Celestijnenlaan 200F, PO Box 2404, 3001 Leuven, Belgium.
Chemistry. 2009;15(3):656-74. doi: 10.1002/chem.200801566.
N-alkyl-N-methylpyrrolidinium cations have been used for the design of ionic liquid crystals, including a new type of uranium-containing metallomesogen. Pyrrolidinium salts with bromide, bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, hexafluorophosphate, thiocyanate, tetrakis(2- thenoyltrifluoroacetonato)europate(III) and tetrabromouranyl counteranions were prepared. For the bromide salts and tetrabromouranyl compounds, the chain length of the alkyl group C(n)H(2n+1) was varied from eight to twenty carbon atoms (n = 8, 10-20). The compounds show rich mesomorphic behaviour: highly ordered smectic phases (the crystal smectic E phase and the uncommon crystal smectic T phase), smectic A phases, and hexagonal columnar phases were observed, depending on chain length and anion. This work gives better insight into the nature and formation of the crystal smectic T phase, and the molecular requirements for the appearance of this highly ordered phase. This uncommon tetragonal mesophase is thoroughly discussed on the basis of detailed powder X-ray diffraction experiments and in relation to the existing literature. Structural models are proposed for self-assembly of the molecules within the smectic layers. In addition, the photophysical properties of the compounds containing a metal complex anion were investigated. For the uranium-containing mesogens, luminescence can be induced by dissolving them in an ionic liquid matrix. The europium-containing compound shows intense red photoluminescence with high colour purity.
N-烷基-N-甲基吡咯烷鎓阳离子已被用于离子液晶的设计，包括一种新型的含铀金属介晶。制备了带有溴化物、双（三氟甲基磺酰）亚胺、四氟硼酸盐、六氟磷酸盐、硫氰酸盐、四（2-噻吩甲酰三氟丙酮）铕（III）和四溴铀酰抗衡阴离子的吡咯烷鎓盐。对于溴化物盐和四溴铀酰化合物，烷基C(n)H(2n+1)的链长从8个碳原子变化到20个碳原子（n = 8, 10 - 20）。这些化合物表现出丰富的介晶行为：根据链长和阴离子的不同，观察到了高度有序的近晶相（晶体近晶E相和不常见的晶体近晶T相）、近晶A相和六方柱状相。这项工作能更好地洞察晶体近晶T相的本质和形成，以及出现这种高度有序相的分子要求。基于详细的粉末X射线衍射实验并结合现有文献，对这种不常见的四方中间相进行了深入讨论。提出了近晶层内分子自组装的结构模型。此外，还研究了含有金属络合阴离子的化合物的光物理性质。对于含铀介晶，将它们溶解在离子液体基质中可诱导发光。含铕化合物表现出强烈的红色光致发光，色纯度高。
