Melon Ring And The Imidazole Derivatives And Methylene Blue Dye Test Of Self-assembly System

Nowadays supramolecular chemistry or host-guest chemistry has become one of the hot fields of chemical research . Just as there is a field of molecular chemistry based on the covalent bond, there is a field of supramolecular chemistry, the chemistry of molecular assemblies and of Host-Guest Chemistry, Molecular Recognition. Cucurbit[n]urils are cyclic methylene-bridged glycoluril oligomers whose shape resembles a pumpkin. The defining features of cucurbit[n]urils are their two portals lined by carbonyl groups that provide entry to their hydrophobic cavity. Due to their special structure, cucurbit[n]urils are becoming a series new hosts after crown ether, cyclodextrin and calixarene, and are one of the important investigation of the supramolecular chemistry.In the first party of the paper, The structures and optical properties of host-guest of cucurbit[n=6-8]urils and tetramethylcucurbit[6]uril with some imidazole derivatives (4-(imidazol-yl)phenol (g1), 4-(imidazole-1-yl)aniline (g2) and 2-phenylimidazole (g3)) have been investigated by ¹H NMR spectroscopy, electronic absorption spectroscopy, fluorescence Spectroscopy and single crystal X-ray diffraction determination. The experimental results reveal that A-N_Q[n]/N_guest data and I_f-N_Q[n]/N_guest data for the same system can be well fitted to the same binding model. Particularly, the A-N_Q[n]/N_guest data and I_f-N_Q[n]/N_guest data and ¹H NMR determination for three Q[6]-g(1-3) systems and Q[7]-g(1-3) all fitted to a 1:1 binding model respectively, Q[8]-g(1-3) systems are all fitted 1:2 binding model respectively.Moreover , the effect of pH for reciprocity between cucurbit[n=6-8]urils and some imidazole derivatives has been investigated. The experimental results reveal that the reciprocity of cucurbit[n=6-8]urils with some imidazole derivatives is remarkable in the condition of 0 < pH < 9.While the pH is higher than 9, the reciprocity of cucurbit[n=6-8]urils with some imidazole derivatives has not been observed by electronic absorption spectroscopy and fluorescence Spectroscopy.In the second party of the paper ,The interaction structures and optical properties of host-guest of cucurbit[n=7-8]urils]uril with Methylene Blue (g) have been investigated by using ¹HNMR technique, fluorescence spectrophotometry and ultraviolet spectrophotometry. The experimental results reveal that Q[7]-g systems and Q[8] all fitted to a 2:1 and 1:2 binding model respectively between pH=0～13.Based on electronic absorption spectroscopy and higher sensitive and selective of supramolecular systems, the detection limit and linear range was determined in order to build up a new fluorimetric method for the analysis.