Studies On The Fluorescent Properties And Weak Interactions Between Metal Complexes And Cucurbiturils

Cucurbituril is a kind of high symmetric pumpkin-shaped organic macrocyclic molecules, including a series of CB5, CB6 CB7 and CB8 with different sizes. Owing to its rigid structural features, they have been widely used as a unique molecular templates or synthetic receptors. In recent years they have already been used to design new assembly system of inorganic-organic hydridized supramolecular structures with specific properties. With the development of supramolecular chemistry, the research on cucurbituril supramolecular chemistry in recent twenty years have also achieved rapid progress as one of the hottest research areas in the supramolecular chemistry frontier.This paper is based on the relevant work of our research group, in the research related to the design of organic macrocyclic pumpkin-shaped (CB5, CB6, CB7 and CB8) supramolecules,through the introduction of magnesium(II), aluminum(Ⅲ) , or zinc(II) -8 - hydroxyquinoline -5- sulfonic acid(Hqs) anion complex, five novel supramolecular crystals have successfully been synthesized, and their superamolecular structures and fluorescencent properties have been analysed. The relationship between the luminescent nature and the supramolecular structures were discussed. According to the structures, the complex Zn(Hqs)2 were templated by the walls of cucurbituril as a unique 2D-helical open-frameworks, and strikingly forms an unusual center-symmetric sandwiching-inclusion to each of the CB6–Na complex cations via the water-assisted helical shape-matching interaction.The crystal structure of [Zn(Hqs)₂][Na₂(CB6)(H₂O)8](1) has been determined by X-ray diffraction method. The results showed that 1 was crystallized in monoclinic, P21/c space group, a = 16.328(3) , b = 13.643(3) ,c = 20.836(8) ,β= 119.35(2) ,V = 4045. 7(2) 3,Z = 1,F(000) = 1952,Dcalc = 1.542 g/cm³,μ= 0.473 mm-1,R1[I>2σ(I)] = 0.0544, wR₂ (all data) = 0.1237; According to the structures, the metal complex of Zn (Hqs)2 , in 1 were templated by CB6 as the unique 2D helical open-frameworks, and strikingly from an unusual center-symmetric sandwiching-inclusion to each of the CB6–Na complex cations via the water-assisted helical shape-matching interaction . Through the ring aromatic stacking interaction with the edge of quinoline ring and the glycoluril ring of CB6 and electrostatic hydrogen bond of the water and ligand, anion complexes matched the shape of large Central CB6, formed unique supramolecular assembly structure. By ultraviolet spectrometry and fluorescence spectroscopic method to study the complexes (1) solution to the coordination balance and fluorescence properties, determination, and through the solid fluorescence crystal supramolecular structures, discusses the large ring CB6 unique supramolecular structure and its action on complexes at the luminous nature significantly structure effect.Further spectral research for adding a series of the large ring CB5,CB6,CB7 and CB8, respectively, to the Zn(II), Mg(II) or Al(Ⅲ)-Hqs complexes has been carried out. The ultraviolet spectrum and fluorescence properties research in solution, for exploring the structural effects of CB5, CB6, CB7 and CB8 on the fluorescenct intensity of the complexes have been found. By referencing the structure of 1, the possible effects of the large ring on the fluorescence of the complexes have been discussed.The present results contribute to the supramolecular chemistry of CBn family with valuable information, and present a future application of cucurbiturils in developing novel luminescent functional materials.