Study On Self-Assembly Properties Of Anionic Tetrahedron Cages With UV Light Stimulated Response

Supramolecular chemistry has attracted much attention in recent years.Molecules went through Recognition,Molecular Self-assembly to form a series of structure and shape controllable assembling constructions,which possessed specific performances and widely used in life science and biology.A series of C₂ symmetry tetraurea anion receptors were designed and prepared in detail in this article.The interaction between receptors and anions was also investigated,especially tetrahedral anions,such as PO₄^3-,SO₄^2-,etc.We attempted constructing anion as a coordination center formed into a variety of supramolecular structures,enforcing the function of guest recognition.The main parts of this article were given as follow:Firstly,based on our previous work and referenced the published literatures,we designed and synthesized C₂ symmetry ligand L with azo group,taking advantage of excellent affinity between ortho-phenylene-bridged oligourea with phosphate anion.We expect Ligand L can coordinate with phosphate anion self-assemble into larger tetrahedron cage A₄L₆.With the aid of azo group sensitive to UV light,we can manage assembly constructions forms through the illuminate of ultraviolet and visible light.And by means of the single crystal structure,NMR,UV spectra and mass spectrometry proved that ligand L can coordinate with phosphate anion and formed tetrahedral cages in solid state and solution state.Two meta-phenylene bridged trisurea ligands with nitrophenyl?L¹?or naphthyl?L²?pendants have been synthesized for anion coordination.The assembly of L¹ with?TBA?₂SO₄,?TBA?H₂PO₄,and?TBA?₂?p-[COO-C₆H₄-COO]?led to three 1D anion coordination polymers?ACPs?,{?TBA?₂[?HPO₄?L¹]×H₂O×2DMSO}_n?1?,{?TBA?₂[?SO₄?L¹]×H₂O}_n?2?,and{?TBA?₆[?p-[COO-C₆H₄-COO]?₃L₂¹]×DMSO}_n?3?.Complexes 1 and 2 are infinite linear 1D polymers,1 and 2 molecule adopts a twisted“U”shape,while 3 adopts an S-shaped conformation instead of the twisted U-shape,resulting in a dimerized“double chain”structure.Treatment of L¹?or L²?with Br^-,AcO^-,BzO^-salts afforded the trinuclear?1:3 ligand to anion?complexes?TBA?₃[A₃L]?4-8,A=anion?.?TBA?₃[Br₃L¹]×THF?4?also adopts a U-shaped conformation with outward-pointing urea NH groups.AcO^-or BzO^-anion complexe form the discrete trinuclear structure.The ligand molecules display considerable flexibility in the structures.Solution binding studies of L¹ and L² toward the anions were carried out by ¹H NMR,UV-vis,and fluorescence titration experiments,from which the binding stoichiometry and stability constants were obtained.we validate these properties.Designed of tetrahedral cages with VOIDOO program to calculate the internal cavity was estimated to be about 400-500?,meanwhile crown ether with potassium could be encapsulated into cavity.So some large guest could be encapsulated.On the edge of tetrahedron because of a "window",therefore it can be used as a guest in and out of the channel,used for application in catalytic reaction.