Begel Svetlana, Puchta Ralph, van Eldik Rudi
Inorganic Chemistry, Department of Chemistry and Pharmacy, University of Erlangen-Nürnberg, Egerlandstr. 1, 91058, Erlangen, Germany.
J Mol Model. 2014 Apr;20(4):2200. doi: 10.1007/s00894-014-2200-1. Epub 2014 Apr 9.
The selectivity of the bis(calix[4]arene)tetraethylene abbreviated as calix[4]tube for the endohedral complexation of alkali and alkaline earth metal ions, was predicted on the basis of structures and complex formation energies computed with three different quantum chemical methods: DFT LANL2DZp)/LANL2DZp), PM3/SPASS, and PM6. A comparison with published X-ray structures demonstrated that the most reliable results were achieved applying DFT calculations. The complexation of K⁺ and Ba²⁺ is most favorable, followed by the encapsulation of Rb⁺ and Sr²⁺, respectively. The flexibility of the tube, described by the torsion angles associated with the ethylene linkages between the calix[4]arene units and phenyl rings intersecting the plane of the four methylene carbon atoms, also makes an important contribution to its selectivity. In general, the cavity size is similar to [2.2.2] and [N2N2N2], the cryptands with the largest cavities previously studied in our group applying a similar protocol.
基于用三种不同量子化学方法（DFT LANL2DZp)/LANL2DZp)、PM3/SPASS和PM6）计算得到的结构和络合形成能，预测了简称为杯[4]管的双（杯[4]芳烃）四乙烯对碱金属和碱土金属离子包结络合的选择性。与已发表的X射线结构比较表明，应用DFT计算可获得最可靠的结果。K⁺和Ba²⁺的络合最有利，其次分别是Rb⁺和Sr²⁺的包封。由与杯[4]芳烃单元之间的乙烯键以及与四个亚甲基碳原子平面相交的苯环相关的扭转角所描述的管的柔韧性，也对其选择性有重要贡献。一般来说，其空腔尺寸与[2.2.2]和[N2N2N2]相似，[2.2.2]和[N2N2N2]是我们小组先前采用类似方案研究的具有最大空腔的穴状配体。
