Amendola Valeria, Miljkovic Ana, Legnani Laura, Toma Lucio, Dondi Daniele, Lazzaroni Simone
Department of Chemistry , University of Pavia , via Taramelli 12 , I-27100 Pavia , Italy.
Inorg Chem. 2018 Apr 2;57(7):3540-3547. doi: 10.1021/acs.inorgchem.7b02534. Epub 2018 Jan 12.
In this work, we employed for the first time a dinuclear bis[tris(2-aminoethyl)amine] cryptate to obtain the self-assembly of pseudorotaxane structures in an aqueous solution. The goal was achieved by exploiting the well-known affinity of the dicopper azacryptate with diphenyl spacers for the terephthalate anion. In particular, a series of molecular threads were synthesized by appending either alkyl or polyoxyethylene chains on both sides of the terephthalate benzene ring. The obtained dicarboxylic acids were precipitated as sodium salts, and their affinity toward the dicopper azacryptate was determined in a methanol/water mixture (pH 7). Experimental investigations showed that the chains' length and nature have a small impact on the 1:1 binding constants, whose values range between 4.98 and 5.18 log units. Computational studies indicated that the molecular axle is threaded through the azacryptate cavity, with the terephthalate group wedged between the two copper ions, coordinating both of them in the apical position (the one that, in the free azacryptate, is occupied by a water molecule). Compared to the inclusion complex with the plain terephthalate anion, a slight strain was found in the pseudorotaxane structure, induced by the inner chain of the thread inside the cavity. These results may be of great interest in all of the fields of science and technology in which host-guest recognition and molecular cages are applied.
在这项工作中，我们首次使用双核双[三（2-氨基乙基）胺]穴状配体，以在水溶液中获得准轮烷结构的自组装。通过利用二铜氮杂穴状配体与带有二苯基间隔基的对苯二甲酸根阴离子的众所周知的亲和力，实现了这一目标。具体而言，通过在对苯二甲酸苯环的两侧连接烷基或聚氧乙烯链，合成了一系列分子链。所得到的二元羧酸以钠盐形式沉淀，并在甲醇/水混合物（pH 7）中测定它们对二铜氮杂穴状配体的亲和力。实验研究表明，链的长度和性质对1:1结合常数的影响较小，其值在4.98至5.18对数单位之间。计算研究表明，分子轴穿过氮杂穴状配体的空腔，对苯二甲酸基团楔入两个铜离子之间，在顶端位置（在游离氮杂穴状配体中被水分子占据的位置）与它们两者配位。与与普通对苯二甲酸根阴离子形成的包合物相比，在准轮烷结构中发现了由空腔内分子链内部引起的轻微应变。这些结果可能在应用主客体识别和分子笼的所有科学和技术领域中具有重大意义。
