Font Size: a A A

Theoretical Studies On Multi-hydrogen Bonds Containing Water Molecules

Posted on:2019-12-18Degree:MasterType:Thesis
Country:ChinaCandidate:Z Y LiuFull Text:PDF
GTID:2381330545497898Subject:Physical chemistry
Abstract/Summary:PDF Full Text Request
Hydrogen bond plays a key role in the field of chemistry and biology.With the formation of hydrogen bond,Water molecule can not only combine with organic molecules to form different geometries,but also as an active participant in reactions.In this paper,the importance of hydrogen bond in chemical field is discussed as two following aspects:1.Theoretical study on multi-hydrogen bonds in tryptamine and water complexes.It is reported that the most stable neutral geometry of tryptamine water complex is formed by two intermolecular hydrogen bonds.In this paper,for the first time,the existence of the third hydrogen bond in the neutral complex was identified,highlighting a single water's role as one proton donor and two proton acceptors as it binds to tryptamine.The energy decomposition fragmentation scheme for the multi-hydrogen bond system is proposed based on the GKS-EDA method.The results show that the interaction of three hydrogen bonds is very different.Upon threshold ionization of neutral complex,the network of the three intermolecular H-bonds is indeed preserved while the individual H-bonds' binding strengths are subject to change.In addition,it is found that the main reason for the transformation of the cationic complex is due to the formation of intramolecular hydrogen bond.2.Energy decomposition analysis on multiple proton transfer via hydrogen-bonded water wire in 3-hydroxypyridine.It is generally believed that the proton transfer reactions tend to take place in excited-state.In chapter 4,proton transfer in 3-hydroxypyridine was studied,it is found that the reaction can occur in the ground state by the assist of hydrogen-bonded water bridge.The energy decomposition method was used to calculate the reaction energy barrier in gas phase and liquid phase,and it is found that the reaction barrier is mainly related to strain energy and polarization energy.Longer water bridge can increase the variation of polarization energy to reducing the reaction energy barrier,but longer water bridges can also increase the strain energy which increasing the reaction energy barrier.GKS-EDA combined with the reaction electronic flux indicates that different water bridges correspond to different reaction mechanisms.The reaction mechanism of the two-molecule water bridge in the transition region is breaking bond process followed by forming bond process,while the mechanism of three water bridge is forming bond followed by the breaking bond process.More results will be presented soon.
Keywords/Search Tags:hydrogen bond, energy decomposition analysis, proton transfer, water wire
PDF Full Text Request
Related items