Macrocycle-Directed Construction of Tetrahedral Anion-p Receptors for Nesting Anions with Complementary Geometry

摘要

Manipulation of the emerging anion-p interactions in a highly cooperative manner through sophisticated host design represents a very challenging task. In this work, unprecedented tetrahedral anion-p receptors have been successfully constructed for complementary accommodation of tetrahedral and relevant anions. The synthesis was achieved by a macrocycle-directed approach by using large macrocycle precursors bearing four reactive sites, which enabled a kinetic-favored pathway and afforded the otherwise inaccessible tetrahedral cages in considerable yields. Crystal structure suggested that the tetrahedral cages have an enclosed three-dimensional cavity surrounded by four electron-deficient triazine faces in a tetrahedral array. The complementary accommodation of a series of tetrahedral and relevant anions including BF_4~-, ClO_4~-, H_2PO_4~-, HSO_4~-, SO_4~(2-) and PF_6~- was revealed by ESIMS and DFT calculations. Crystal structures of ClO_4~- and PF_6~- complexes showed that the anion was nicely encapsulated within the tetrahedral cavity with up to quadruple cooperative anion-π interactions by an excellent shape and size match. The strong anion-π binding was further confirmed by negative ion photoelectron spectroscopy measurements.