8 - Hydroxyquinoline And Quantum Chemical Study Of The Schiff Base

The proton transfer, one of the most fundamental and important phenomenon in biochemical processes, has been investigated extensively such as the energy conversion, the identification of protein and receptor on substrates intermediates. The Schiff bases containing 8-hydroxyquinoline unit are important in many aspects because of their special properties, such as biological activity, catalytic activity, optical activity, etc. In this paper, three kinds of proton transfer reactions (intramolecular proton transfer (PT), water-assisted PT, and methanol-assisted PT) of three Schiff bases containing 8-hydroxyquinoline unit, have been researched with B3LYP/6-31+G(d) basis set level.ChapterⅠ:A brief review is introduced about Schiff bases containing 8-hydroxyquinoline unit and proton transfer researches in recent years.ChapterⅡ:The intramolecular proton transfer (PT), the water-assisted PT, and the methanol-assisted PT of 2-[(4-chlorophenylimino) methyl]-8-hydroxyquinoline are investigated. Based on the crystal structure of the Schiff base compounds, the steady states and the transition states of PT process are optimized with B3LYP/6-31+G(d) basis set level. The primary geometry structures, infrared frequencies, energies, as well as the NMR data are studied. It implies that both the water and methanol are favorable for PT owing to their capability to reduce significantly the PT energy barriers. The H-bond plays a key role in decreasing the activation energy.ChapterⅢ:The intramolecular PT, the water-assisted PT, and the methanol-assisted PT of 2-[(4-brominephenylimino) methyl]-8-hydroxyquinoline are investigated. Based on the crystal structure of the Schiff base compounds, the steady states and the transition states of PT process are optimized with B3LYP/6-31+G(d) basis set level. The primary geometry structures, infrared frequencies, energies, as well as the NMR data are studied. It implies that both the water and methanol are favorable for PT owing to their capability to reduce significantly the PT energy barriers. The H-bond plays a key role in decreasing the activation energy.ChapterⅣ:The intramolecular PT, the water-assisted PT, and the methanol-assisted PT of 2-[(4-fluorinephenylimino)methyl]-8-hydroxyquinoline are investigated with B3LYP/6-31+G(d) basis set level. The steady states and the transition states of PT process are optimized. The primary geometry structures, infrared frequencies, energies, as well as the NMR data are studied. It implies that both the water and methanol are favorable for PT owing to their capability to reduce significantly the PT energy barriers. The H-bond plays a key role in decreasing the activation energy. The results show that the proton transfer reactions of the three compounds are similar, the difference of halo-substituted group does not make much influence on the proton transfer reactions.