Self - Assembly Of Tetrahedral Anion Cages And Study On The Nature Of Host And Object

Over the past few decades, the chemistry in a confined space has attracted much interest in many applications, including recognition and separation of a guest, stabilization of reactive molecules or reaction intermediates, drug delivery, biomolecular sensing, catalysis, etc. Chemists have devoted much effort to create enforced cavities, such as the zeolite-like complexes, organic (covalent) cages, metal coordination complexes, and noncovalent organic frameworks. In particular, the discrete molecular cages have been extensively studied in the host-guest chemistry. The majority of caged structure is based on metal coordination, with a small portion of covalent systems. Reference the published literatures, we can know the anion as a coordination center can be formed into a variety of supramolecular structures. In this paper, we study on phosphate anion-coordination-based self-assembly tetrahedral cages and the interaction between the host and guest, including the following:First, Based on our previous work, we design and synthesized C3 symmetry ligand L, take advantage of ortho-phenylene-bridged oligourea, which display excellent affinity and complementarity to the tetrahedral sulfate and phosphate anions. We expect that ligand L can coordinate with phosphate anion self-assemble into larger tetrahedron cage 1. A DFT modulation of L proved evidence that it can form a tetrahedral cage with PO43-. And by means of single crystal structure, mass spectrometry and NMR techniques prove that ligand L can coordinate with phosphate anion and forming tetrahedral cages.Second, the targeted guests were quasi-tetrahedral, which may cause damages to the environment and human health, Freon components (CFCl3, CF2Cl2, CHFC12, and C(CH3)F3), the chlorocarbons (CH2C12, CHC13, CCl4, C(CH3)C13, C(CH3)2Cl2, and C(CH3)3Cl) and highly unstable white phosphorus (especially the highly challenging Freons and white phosphorus) in consideration of the good match in:1) shape; 2) size; and 3) electronic properties, between the guest and host. First, they have an excellent shape complementarity. Second, the internal cavity of cage 1 was estimated to be about 229 A3, while the volume of a series of halocarbons falls in the range of 71 to 134 A3 (see Supporting Information), thus proving the match of the size. Last, ligand L features an electron-rich triphenylbenzene spacer, which would be further reinforced upon coordination with phosphate, thus favoring the interaction with the electronegative halogen atoms. The guest encapsulation in the solid state is confirmed by crystal structures, while the host-guest interactions in solution were demonstrated by NMR techniques. We report the first examples of the inclusion chemistry of an anion-coordination-based cage structure. The results represent a new concept for constructing confined space for the inclusion of specific guests based on anion coordination, a field of increasing interest and developing rapidly.