Institute of Chemical Research of Catalonia (ICIQ) , Avda. Països Catalans 16, 43007 Tarragona, Spain.
J Am Chem Soc. 2015 Feb 11;137(5):2047-55. doi: 10.1021/ja512590j. Epub 2015 Feb 2.
The synthesis, structural characterization, and binding properties of two unprecedented multitopic receptors for ion-pair recognition are described. We isolated two of the six possible diastereomeric deep cavitand receptors resulting from the installation of four phosphonate groups at the upper rim of a calix[4]pyrrole-resorcin[4]arene hybrid scaffold. The isolated tetra-phosphonate receptors display either three (iooo) or four (oooo) of their P═O groups oriented away from the deep and functionalized aromatic cavity. In contrast to analogous tetra-phosphonate resorcin[4]arene cavitands, the 14-membered macrocyclic rings that contain the P═O groups in the tetra-phosphonate calix[4]pyrrole cavitands are conformationally flexible, always adopting a conformation locating the phenyl substituents in equatorial position. The tetra-phosphonate calix[4]pyrroles exhibited larger affinity constants than the previously reported bis-phosphonate calix[4]pyrrole counterparts in the complexation of both tetramethylphosphonium and octylammonium chloride salts in nonpolar solvents. We demonstrated that the iooo diastereoisomer was able to function as a multitopic receptor for organic chloride salts by switching the geometry of the 1:1 ion-paired complex from receptor-separated to close-contact depending on the quaternary or primary nature of the cobound organic cation. The ion-paired 1:1 complexes formed between the diastereomeric receptors and organic chloride salts were studied and thermodynamically characterized in solution. The determined stability constant values were compared to those obtained for the bis-phosphonate counterparts. The structure of the TMPCl⊂7iooo complex was determined by X-ray structure, and its formation was also evidenced in the gas phase.
描述了两种前所未有的用于离子对识别的多功能受体的合成、结构表征和结合特性。我们从杯[4]吡咯-间苯二酚[4]芳烃杂化支架的上边缘安装四个膦酸酯基团，分离出两种可能的非对映立体异构深穴受体中的两种。分离出的四膦酸酯受体显示其三个（iooo）或四个（oooo）的 P ═ O 基团远离深且功能化的芳族空腔。与类似的四膦酸酯间苯二酚穴醚相比，包含 P ═ O 基团的 14 元大环环在四膦酸酯杯[4]吡咯穴醚中是构象柔性的，总是采用将苯基取代基定位在赤道位置的构象。四膦酸酯杯[4]吡咯在非极性溶剂中对四甲基磷𬭩和辛基氯化铵盐的络合表现出比先前报道的双膦酸酯杯[4]吡咯类似物更大的亲和常数。我们证明，iooo 非对映异构体能够作为多功能受体，通过根据共结合有机阳离子的季铵或伯性质，将 1:1 离子对配合物的几何形状从受体分离切换到紧密接触，从而对有机氯化物盐起作用。研究并热力学表征了非对映异构体受体与有机氯化物盐之间形成的离子对 1:1 配合物。确定的稳定常数值与双膦酸酯对应物的值进行了比较。通过 X 射线结构确定了 TMPCl⊂7iooo 配合物的结构，并在气相中也证明了其形成。
