Study On The Molecular Recognition Of Cucurbiturils For Their Applications In Chromatography And Others

Molecular recognition is the core of supramolecular system. It also is the formation foundation of supramolecular structure. It is defined as highly selective interactions between host and guest through space match to produce a series of special functions. Many analytical chemists, medicinal chemist and environmental chemists at home and abroad have paid more attention to host-guest chemistry because it has great application potential in chromatographic separation material, drug carrier and environmental pollution treatment. After crown ethers, cyclodextrins and calixarenes, cucurbit[n]uril (CB[n],n=5～10) is the fourth generation of new supramolecule with unique cavity structure and carbonyl groups. Cucurbiturils has been proved to be new ideal supramolecules with a wide range of guests including both organic cations and molecules. In this thesis, CB[7] was used as ligand of GC stationary phase in packed column for the first time. Its chromatographic performance was systematically studied. Meanwhile, it is also found that CB[7] is excellent drug carries of purines and pollutant scavenger of dyes based on molecular recognition study by fluorescence spectrometric and UV-spectroscopic methods, respectively. The main contents studied are as follows:1. The structural features and synthesis of CB[n] family were comprehensively reviewed. The main subject focused on the study of their molecular recognition. The application prospect of cucurbiturils for separation science and other related techniques was discussed. all works were considered as the theoretical base and the further research of the thesis.2. At present, the synthesis and purification of the CB[n] is still rather difficult work. Based on previous work, we improved on the process by the using of paraformaldehyde instead of 40% formaldehyde solution and a two-step purification approach of water-hydrochloric acid. This method can simplify the preparation process, promote yield of CB[7], reduce consumption amount of hydrochloric acid, protect our environment and save production costs. This provided enough CB[7] material for the preparation of CB[7] GC stationary phases and study on its molecular recognition.3. A packed column coated with cucurbit[7]uril 1(CB[7]) (3.2 mm×2.1m) for GC was first prepared. Its basic chromatographic properties were studied by using different probes. The chromatographic retention mechanism of the CB[7] stationary phase was preliminary discussed. The results showed that the CB[7] stationary phase can be used under high column temperature, and exhibit outstanding thermostability and high selectivity for most analytes, such as aromatic hydrocarbons, halogerated hydrocarbons, ketones, esters, siloxanes, etc. Especially it can easily separate some positional isomers of alcohols and the high boiling point esters and siloxanes within 7 min. The packed column can maintain a stable baseline while heating rate at 150℃·min-1. CB[7] was a good high temperature stationary phase due to special chemical structure and various interactions, including the inclusion of gaseous analytes.4. In addition to separation function, CB[7] is also a new drug carrier. The interaction between CB[7] and bovine serum albumin(BSA) was studied by fluorescence spectrometric method. It was found that at physiological pH 7.4, the intrinsic fluorescence quenching of BSA were observed as adding of CB[7]. The quenching constant decreased with increasing temperature. The fluorescence quenching data were analyzed according to Stern-Volmer equation and Lineweaver-Burk double-reciprocal equation. The binding constant, binding site number and thermodynamic parameters were obtained at different temperature. The apparent binding constant (KA) was 2.3367×105 Lmol-1 with binding sites(n) 1.078 at 298K. Based on the thermodynamic parameter analysis, it can be concluded that the hydrophobic and electrostatic interactions were main force between CB[7]and BSA. The partial inclusion between the hydrophobic cavity from CB[7] to the hydrophobic amino acid residues on the BSA and electrostatic interactions maintained the stability of CB[7]-BSA. Synchronous fluorescence indicated that CB[7] did not cause the conformation changes of BSA, It can provide useful information for the utilization of CB[7] in the field of biology and drug carriers.5. The inclusion interactions of CB[7] with 6-mercaptopurine (6-MP)and adenine (ADP) were studied by fluorescence spectrometric method. Several effect factors such as time, the pH values and temperature on the fluorescent intensity and the stability of the complex were investigated. The complex constants of CB[7] with 6-MP and ADP were determined according to the Benesi-Hildebrand equation, respectively. The results indicated that the pH value had a significant effect on the inclusion interactions. At the presentence of CB[7] both 6-MP at pH 8.0 and ADP at pH 2.0 reached the optimal and stable excitation and emission wavelength within 5 min. With the increasing of the concentrations of CB[7], the fluorescent intensity of the two complexes enhenced obviously. Their inclusion constants were 3.6797x102 Lmol-1 for 6-MP-CB[7]and 2.2033×102 Lmol-1 for ADP-CB[7] at 298K with the same inclusion ratio of 1:1. The main interaction forces between CB[7] and the above purines were discussed based on the thermodynamic parameters. CB[7] is only well water-soluble superamolecules among cucurbituril family members. It will has great application potental in drug carriers with safety and low toxicity.6. The inclusion interactions of CB[7] with three water-soluble direct dyes such as scarlet red, peach red, bordeaux red were studied by UV/Vis spectroscopic method, respectively. It was found that the absorbance of the three water-soluble direct dyes decreased obviously and all of them have a equal point as adding of CB[7]. Several effect factors, such as the concentration of CB[7], the pH values, temperatures, common organic solvents and surfactants on the absorbance of dyes were investigated. The results showed that the stable complexes can be formed between CB[7] and three water-soluble direct dyes, respectively. The formation of stable complexes was due to partial inclusion interaction between CB[7] with the group of dyes. All complexes have the same ratio of 1:1, which were determined by equimolar ratio and Job methods. According to the thermodynamic parameters it can be concluded that the inclusion interaction is a exothermic process with the hydrophobic and hydrogen bonding forces.