Study On Intramolecular Proton Transfer For Quinazolinone Compounds

Proton transfer refers to the process of the H transfer from offering proton functional group to accepting proton functional group, because it is the important biochemical processes, it has received the widespread attention and research. In addition, the excited state proton transfer is a kind of important reactions in photochemical and optical physics. By quantum chemistry calculation methods, this paper discusses the proton transfer of quinazolinone coppounds and the impact of nano limit media on the proton transfer. On this basis, adopting the method of combining theory and experiment, we also examined the effect of supramolecular cucurbit[7]uril on the HPQ proton transfer. The main results are as follows:1? The intramolecular proton transfer reactions of 2-(2,5-dihydroxyphenyl)--4(3H)-quinazolinone(DHPQ) has been studied at B3LYP/6-311++G(d) level. The effect of nanoconfined media on DHPQ proton transfer has also been explored by using ONIOM model(b3lyp/6-311++g(d): pm3). The results show that DHPQ exists the possibility of double proton transfers. According to the reaction mechanism analysis, the double proton transfers process in DHPQ carried out step by step. There are two matching relations when DHPQ interacts with CB7, the limit of nano cavity produced a large energy barrier, inhibiting the intramolecular proton transfer process, and the introduction of water solvent promoted the path 2 but inhibited path 1.2?With quantum chemical calculation methods, we study the intramolecular proton transfer progress of 2-(3-Hydroxy-2-pyridinyl)-4(1H)-quinazolinone(HPQZO) at B3LYP/6-311++G(d) level and the effect of nanoconfined media on HPQZO proton transfer. The results show that the double proton transfers process in HPQZO carried out step by step, and the transfer of H1 is more easilier than H3. CB7 with HPQZO in the way of two matching relations was discussed by using ONIOM model.The results show that [HPQZO]b is the minimum energy, and cucurbit[6]uril can increase the proton transfer barrier of [HPQZO]a, so it produces inhibiting influence, however, it has promoting effect on [HPQZO]b. When discussing solvent effect, There are compeletely different conclusions between [HPQZO]a and [HPQZO]b, in all, contrasting the gas phase with the solvent phase, the solvent effect shows inhibiting performance for [HPQZO]a and promoting performance for [HPQZO]b.3?2-(2-hydroxyphenyl)quinazolin-4(3H)-one(HPQ) was synthesized and characterized, the spectroscopic properties of HPQ with CB7 was monitored by using fluorescence emission spectrum and transient fluorescence spectra, in order to analyse the effect of nanoconfined media on the excited-state proton transfer. The fluorescence spectrum shows that HPQ interacts with CB7 very well, and they combined with each other in the stoichiometry 1:1. That HPQ displays double fluorescence emission peaks gives the possibility of studying interaction between HPQ with CB7.In the solvent dependent study, after HPQ contacts with different solvents, the fluorescence emission peak and its intensity have had great changes. It is in favor of excited state intramolecular proton transfer reaction when HPQ is distributed in the low polar or protic solvents. Changing p H value qradually, HPQ shows double fluorescence emission peaks in acid solution and single peaks in base solution, which makes clear that the base environment inhibit the intramolecular proton transfer of HPQ when adding CB7 into HPQ, it displays the only peak of long wave, and the fluorescence intensity increases along with the CB7, which proves CB7 can promote intramolecular proton transfer process. Transient fluorescence spectra shows that the fluorescence lifetime of HPQ was decreased when CB7 was titrated in tetrahydrofuran. However, the quantum yield increases, at the same time, the fluorescence intensity was also raised.