The Study On Proton Transfer Of 2-substituted Benzothiazole In The Cucurbit[n]uril

Proton transfer is a kind of basic reaction, which widely present in chemical and biochemical fields, such as halogenated chemical reactions, oxidation reactions, the information transmission among the cells in biological, and the mutation between nucleic acids and bases, and so on. Therefore, it is of significance to study proton transfer. In this paper, through the combination of theory and practice means, the effects of solvent type, pH value and macrocyclic compounds on the proton transfer of 2-substituted benzothiazole compounds was investigated.1. The effects of solvent and cucurbit[7]uril(CB7) on proton transfer for 2-(2-hydroxyphenyl)benzothiazole(HBT) were investigated by using fluorescence emission spectrum, and the influences of the CB7 on the quantum efficiency and lifetime for HBT were also investigated by using transient fluorescene spectrum. At the same time, the forms of interactions between CB7 and HBT were simulated on the level of ?B97XD/6-31G(d, p). The results indicated that the solvents have a great influence on proton transfer of HBT, in the polar solvent, HBT is easy to form the phenolic oxygen anion with the interactions between solvents, while in the nonpolar solvent, HBT is gradually transformed from an alcohol to a ketone structure. By adding the CB7, we found that in the solvent of N,N-dimethylformamide, the formation of the phenolic oxygen anion was promoted, but in the solvent of dichloromethane, the proton transfer efficiency was reduced, Meanwhile, the addition of the CB7 reduced the fluorescence lifetime and increased the quantum efficiency. Through theoretical calculations and the fitting of the Benesi-Hildebrand equation, we found that no matter in solvent or in the gas phase, both CB7 and HBT were able to form the inclusion complexes with 1:1 ration.2. The photophysical properties of 2-(2-aminophenyl)benzothiazole(APBT) in different solvents anddifferent pH were investigated by fluorescence emission spectrum, quantum chemical calculations and 1H NMR spectrum. The results showed that the type and pH solvents have a great influence on fluorescence emission spectrum for APBT. Through the investigation of the interactions with CB7, we discovered that the addition of CB7 has inhibitory effect on the proton transfer of APBT, and it has effect on fluorescence lifetimes and quantum yields of APBT. According to Benesi-Hildebrand equation and quantum chemical calculations, APBT and CB7 formed a inclusion complexes with stoichiometric ratio of 1:1, and the 1H NMR spectroscopy showed that the end of benzothiazole of APBT entered into the nano hydrophobic cavity of CB7.3. The compounds of 2-(2-amino-3-pyridyl)benzothiazole(2A3PyBT) were synthesized and characterized, and the influences of the solvent and p H on its proton transfer were researched. The proton transfer was easily occurred in nonpolar solvents, and the efficiency of proton transfer was higher under acidic conditions, compared with that of in the alkaline solvent. The fluorescent emission spectra of interaction between 2A3 PyBT and CB7 showed that CB7 and 2A3 PyBT formed the inclusion complexes with a ratio of 1:1, while CB8 and 2A3 PyBT formed the inclusion complexes with a ratio of 1:2. Meanwhile, from two aspects of theory and experiment, we illustrated the effects of the macrocyclic compound on proton transfer of 2A3 PyBT by the combination of quantum chemistry theory calculation and experiment.