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Concerted versus stepwise mechanisms of cyclic proton transfer:Experiments, simulations, and current challenges
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作者 程奕涵 朱禹丞 +1 位作者 李新征 方为 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第1期36-50,共15页
Proton transfer(PT) is a process of fundamental importance in hydrogen(H)-bonded systems. At cryogenic or moderate temperatures, pronounced quantum tunneling may happen due to the light mass of H. Single PT processes ... Proton transfer(PT) is a process of fundamental importance in hydrogen(H)-bonded systems. At cryogenic or moderate temperatures, pronounced quantum tunneling may happen due to the light mass of H. Single PT processes have been extensively studied. However, for PT involving multiple protons, our understanding remains in its infancy stage due to the complicated interplay between the high-dimensional nature of the process and the quantum nature of tunneling. Cyclic H-bonded systems are typical examples of this, where PT can happen separately via a “stepwise” mechanism or collectively via a “concerted” mechanism. In the first scenario, some protons hop first, typically resulting in metastable intermediate states(ISs) and the reaction pathway passes through multiple transition states. Whilst in the concerted mechanism, all protons move simultaneously, resulting in only one barrier along the path. Here, we review previous experimental and theoretical studies probing quantum tunneling in several representative systems for cyclic PT, with more focus on recent theoretical findings with path-integral based methods. For gas-phase porphyrin and porphycene, as well as porphycene on a metal surface, theoretical predictions are consistent with experimental observations, and enhance our understanding of the processes. Yet, discrepancies in the PT kinetic isotope effects between experiment and theory appear in two systems,most noticeably in water tetramer adsorbed on NaCl(001) surface, and also hinted in porphycene adsorbed on Ag(110)surface. In ice Ih, controversy surrounding concerted PT remains even between experiments. Despite of the recent progress in both theoretical methods and experimental techniques, multiple PT processes in cyclic H-bonded systems remain to be mysterious. 展开更多
关键词 quantum tunneling proton transfer hydrogen bonding
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Deep-red and near-infrared organic lasers based on centrosymmetric molecules with excited-state intramolecular double proton transfer activity
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作者 Chang-Cun Yan Zong-Lu Che +2 位作者 Wan-Ying Yang Xue-Dong Wang Liang-Sheng Liao 《Opto-Electronic Advances》 SCIE EI CAS CSCD 2023年第7期19-28,共10页
Organic lasers that emit light in the deep-red and near-infrared(NIR)region are of essential importance in laser communication,night vision,bioimaging,and information-secured displays but are still challenging because... Organic lasers that emit light in the deep-red and near-infrared(NIR)region are of essential importance in laser communication,night vision,bioimaging,and information-secured displays but are still challenging because of the lack of proper gain materials.Herein,a new molecular design strategy that operates by merging two excited-state intramolecular proton transfer-active molecules into one excited-state double proton transfer(ESDPT)-active molecule was demonstrated.Based on this new strategy,three new materials were designed and synthesized with two groups of intramolecular resonance-assisted hydrogen bonds,in which the ESDPT process was proven to proceed smoothly based on theoretical calculations and experimental results of steady-state and transient spectra.Benefiting from the effective six-level system constructed by the ESDPT process,all newly designed materials showed low threshold laser emissions at approximately 720 nm when doped in PS microspheres,which in turn proved the existence of the second proton transfer process.More importantly,our well-developed NIR organic lasers showed high laser stability,which can maintain high laser intensity after 12000 pulse lasing,which is essential in practical applications.This work provides a simple and effective method for the development of NIR organic gain materials and demonstrates the ESDPT mechanism for NIR lasing. 展开更多
关键词 excited-state intramolecular proton transfer organic laser near-infrared emission molecular design
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Amide proton transfer imaging of Alzheimer's disease and Parkinson's disease
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作者 Chunmei Li Jinyuan Zhou +7 位作者 Di Wang Xinyang Li Shanshan Jiang Yi Zhang Zhibo Wen Guangbin Wang Fuhua Yan Min Chen 《Magnetic Resonance Letters》 2023年第1期22-30,I0002,共10页
Amide proton transfer (APT) magnetic resonance imaging (MRI) is an important molecularimaging technique at the protein level in tissue. Neurodegenerative diseases have a highlikelihood of causing abnormal protein accu... Amide proton transfer (APT) magnetic resonance imaging (MRI) is an important molecularimaging technique at the protein level in tissue. Neurodegenerative diseases have a highlikelihood of causing abnormal protein accumulation in the brain, which can be detectedby APT MRI. This article briefly introduces the principles and image processing technologyof APT MRI, and reviews the current state of research on Alzheimer's disease and Parkinson's disease using this technique. Early applications of this approach in these twoneurodegenerative diseases are encouraging, which also suggests continued technicaldevelopment and larger clinical trials to gauge the value of this technique. 展开更多
关键词 Amide proton transfer imaging MRI Alzheimer's disease Parkinson's disease
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Experimental and Theoretical Investigation on Excited State Intramolecular Proton Transfer Coupled Charge Transfer Reaction of Baicalein
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作者 胡闪闪 刘琨 +2 位作者 丁倩倩 彭伟 陈茂笃 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2014年第1期51-56,I0003,共7页
The excited state intramolecular proton transfer (ESIPT) coupled charge transfer of baicalein has been investigated using steady-state spectroscopic experiment and quantum chemistry calculations. The absence of the ... The excited state intramolecular proton transfer (ESIPT) coupled charge transfer of baicalein has been investigated using steady-state spectroscopic experiment and quantum chemistry calculations. The absence of the absorption peak from S1 excited state both in the experi-mental and calculated absorption spectra indicates that S1 is a dark state. The dark excited state S1 results in the very weak fluorescence of solid baicalein in the experiment. The fron- tier molecular orbital and the charge difference densities of baicalein show clearly that the S1 state is a charge-transfer state whereas the S2 state is a locally excited state. The only one stationary point on the potential energy profile of excited state suggests that the ESIPT reaction of baicalein is a barrierless process. 展开更多
关键词 Excited state intramolecular proton transfer Intramolecular charge transfer Time-dependent density functional theory Dark state BAICALEIN
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Excited-State Proton Transfer and Decay in Hydrogen-Bonded Oxazole System: MS-CASPT2//CASSCF Study
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作者 谢斌斌 李春香 +1 位作者 崔刚龙 方道 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2016年第1期38-46,I0001,共10页
Herein we have employed high-level multi-reference CASSCF and MS-CASPT2 electronic structure methods to systematically study the photochemical mechanism of intramolecularly hydrogen-bonded 2-(2'-hydroxyphenyl)-4-me... Herein we have employed high-level multi-reference CASSCF and MS-CASPT2 electronic structure methods to systematically study the photochemical mechanism of intramolecularly hydrogen-bonded 2-(2'-hydroxyphenyl)-4-methyloxazole. At the CASSCF level, we have optimized minima, conical intersections, minimum-energy reaction paths relevant to the excited-state intramolecular proton transfer (ESIPT), rotation, photoisomerization, and the excited-state deactivation pathways. The energies of all structures and paths are refined by the MS-CASPT2 method. On the basis of the present results, we found that the ESIPT process in a conformer with the OH... N hydrogen bond is essentially barrierless process; whereas, the ESIPT process is inhibited in the other conformer with the OH... O hydrogen bond. The central single-bond rotation of the S1 enol species is energetically unfavorable due to a large barrier. In addition, the excited-state deactivation of the S1 keto species, as a result of the ultrafast ESIPT, is very efficient because of the existence of two easily-approached keto S1/S0 conical intersections. In stark contrast to the S1 keto species, the decay of the S1 enol species is almostly blocked. The present theoretical study contributes valuable knowledge to the understanding of photochemistry of similar intramolecularly hydrogen-bonded molecular and biological systems. 展开更多
关键词 Excited state proton transfer PHOTOISOMERIZATION Conical intersection Ab initio PHOTOCHEMISTRY
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MP2 Study on the Proton Transfer Mechanism of Glycine Assisted by Water 被引量:3
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作者 孟祥军 《Chinese Journal of Structural Chemistry》 SCIE CAS CSCD 2009年第7期903-909,共7页
The geometries of glycine-nH2O (n = 1-5) complexes and the transition states of proton transfer in glycine-H2O system were calculated at the MP2/6-31++G**//MP2/6-31G* level, upon which we discovered the proton ... The geometries of glycine-nH2O (n = 1-5) complexes and the transition states of proton transfer in glycine-H2O system were calculated at the MP2/6-31++G**//MP2/6-31G* level, upon which we discovered the proton transfer mechanisms, including the number of water molecules necessary for the stabilization of zwitterions and the effect of increasing water molecules on the proton transfer. To our interest, we found that only one water molecule can stabilize the zwitterions; in addition, with the increment of water molecules, the activation energy of positive reaction decreases and that of reverse reaction increases gradually. Glycine will be ionized completely while the water molecules reach to a certain number. 展开更多
关键词 MP2 GLYCINE ZWITTERIONS proton transfer IONIZATION
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Theoretical Studies on the Hydrogen Bond Transfer and Proton Transfer between Anamorphoses of the Dihydrated Glycine Complex 被引量:3
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作者 WANG Ke-Cheng MENG Xiang-Jun SHI Jin LI Bing-Huan 《Chinese Journal of Structural Chemistry》 SCIE CAS CSCD 北大核心 2007年第5期580-586,共7页
The conversion between anamorphoses of the dihydrated glycine complex was studied by means of B3LYP/6-31++G^**. It was found that proton transfer was accompanied by hydrogen bond transfer in the process of convers... The conversion between anamorphoses of the dihydrated glycine complex was studied by means of B3LYP/6-31++G^**. It was found that proton transfer was accompanied by hydrogen bond transfer in the process of conversion between different kinds of anamorphoses. With proton transfer, the electrostatic action was notably increased and the hydrogen-bonding action was evidently strengthened when the dihydrated neutral glycine complex converts into dihydrated zwitterionic glycine complex. The activation energy required for hydrogen bond transfer between dihydrated neutral glycine complexes is very low (6.32 kJ·mol^-1); however, the hydrogen bond transfer between dihydrated zwitterionic glycine complexes is rather difficult with the required activation energy of 13.52 kJ·mol^-1 due to the relatively strong electrostatic action. The activation energy required by proton transfer is at least 27.33 kJ·mol^-1, higher than that needed for hydrogen bond transfer. The activation energy for either hydrogen bond transfer or proton transfer is in the bond-energy scope of medium-strong hydrogen bond, so the four kinds of anamorphoses of the dihydrated glycine complex could convert mutually. 展开更多
关键词 intermolecular interaction B3LYP glycine hydrogen bond transfer proton transfer
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Pattern recognition and data mining software based on artificial neural networks applied to proton transfer in aqueous environments 被引量:2
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作者 Amani Tahat Jordi Marti +1 位作者 Ali Khwaldeh Kaher Tahat 《Chinese Physics B》 SCIE EI CAS CSCD 2014年第4期410-421,共12页
In computational physics proton transfer phenomena could be viewed as pattern classification problems based on a set of input features allowing classification of the proton motion into two categories: transfer 'occu... In computational physics proton transfer phenomena could be viewed as pattern classification problems based on a set of input features allowing classification of the proton motion into two categories: transfer 'occurred' and transfer 'not occurred'. The goal of this paper is to evaluate the use of artificial neural networks in the classification of proton transfer events, based on the feed-forward back propagation neural network, used as a classifier to distinguish between the two transfer cases. In this paper, we use a new developed data mining and pattern recognition tool for automating, controlling, and drawing charts of the output data of an Empirical Valence Bond existing code. The study analyzes the need for pattern recognition in aqueous proton transfer processes and how the learning approach in error back propagation (multilayer perceptron algorithms) could be satisfactorily employed in the present case. We present a tool for pattern recognition and validate the code including a real physical case study. The results of applying the artificial neural networks methodology to crowd patterns based upon selected physical properties (e.g., temperature, density) show the abilities of the network to learn proton transfer patterns corresponding to properties of the aqueous environments, which is in turn proved to be fully compatible with previous proton transfer studies. 展开更多
关键词 pattern recognition proton transfer chart pattern data mining artificial neural network empiricalvalence bond
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Excited State Intramolecular Proton Transfer of 1-Hydroxyanthraquinone 被引量:1
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作者 Si-mei Sun Song Zhang +3 位作者 Kai Liu Ya-ping Wang Miao-miao Zhou Bing Zhang 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2015年第5期-,共7页
关键词 proton transfer Conical intersection Transient absorption spectroscopy 1-Hydroxyanthraquinone
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Theoretical Study of Impact of Side Substituent Effecton Intramolecular Proton Transfer of Perylenequinone
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作者 Ying QIAN Yan WANG Ruo Zhuang LIU(Department of Chemical and Environmental Engineering, Beijing Polytechnic University, Beliing100022)(Department of Chemistry, Beijing Normal University, Beijing 100875) 《Chinese Chemical Letters》 SCIE CAS CSCD 1999年第4期317-320,共4页
Semi-empirical molecular orbital theory AMI method is employed to study the ortho-position substituent impact on intramolecular proton transfer reaction of perylenequinone. The calculation demonstrates that the peryle... Semi-empirical molecular orbital theory AMI method is employed to study the ortho-position substituent impact on intramolecular proton transfer reaction of perylenequinone. The calculation demonstrates that the perylenequinone molecule is of stable structure. and all substituents may cause the decrease of barriers for the hydrogen transfer reaction. 展开更多
关键词 perylenequinone AM1 method proton transfer substituent effect
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Theoretical Study on Intramolecular Proton Transfer of Perylenequinonoid Derivatives
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作者 LiangSHEN DeZhanCHEN 《Chinese Chemical Letters》 SCIE CAS CSCD 2004年第11期1383-1386,共4页
Intramolecular proton transfer of hypomycin A in the ground state S0 and singlet excited state S1 were calculated by high level quantum chemical method in this letter. It was found that the IPT barriers for I→TS1 ar... Intramolecular proton transfer of hypomycin A in the ground state S0 and singlet excited state S1 were calculated by high level quantum chemical method in this letter. It was found that the IPT barriers for I→TS1 are 38.56 kJ/mol in S0 and 8.19 kJ/mol in S1, while those for I→TS4 get approximately 17 kJ/mol higher in S0 and 28 kJ/mol higher in S1. The calculation of IPT rate constants suggests that the experiment observed process of PQD is in S1. The height of the IPT barriers correlate not only with the variance of charge for labile hydrogen, the change of H-bonds length, the change of O-H bonds length and the change of O-O distance, but also with the reactant molecular H-bonds length. Moreover, the correlations are the same for S0 and S1. 展开更多
关键词 Perylenequinonoid derivatives hypomycin A intramolecular proton transfer quantum chemical calculation.
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Theoretical Studies on the Proton Transfer Mechanism in Four-water Hydrated Glycine Complexes
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作者 孟祥军 赵红丽 琚行松 《Chinese Journal of Structural Chemistry》 SCIE CAS CSCD 2012年第5期695-703,共9页
The mp2/6-31++g^**//b3lyp/6-31++g^** method has been employed to study the proton transfer mechanism in 4H2O-glycine complexes(4W-G).Compared with bare glycine the four-water hydrated neutral glycine comple... The mp2/6-31++g^**//b3lyp/6-31++g^** method has been employed to study the proton transfer mechanism in 4H2O-glycine complexes(4W-G).Compared with bare glycine the four-water hydrated neutral glycine complexes(4W-GN) can turn into the corresponding zwitterionic glycine(4W-GZ) through proton transfer.The most stable conformation of 4W-GZ has a "double water-chain" structure and is more stable than its corresponding precursor 4W-GN by 0.97 KJ/mol though it is less stable than the most stable 4W-GN by 7.80 KJ/mol.It is a spontaneous reaction to form the most stable conformation of 4W-GZ,and the potential barrier is only 1.97 KJ/mol,so the probability of this reaction is very high and the most stable 4W-GZ may be detected in experiment or in the early stage of experiment. 展开更多
关键词 GLYCINE HYDRATION ZWITTERION proton transfer bi-water molecule chain
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Proton Transfer Isomerization of Pyrazole in the Ground State:σ vs π Mechanism and Water Assisting Effect
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作者 李志强 步宇翔 赵显 《Chinese Journal of Structural Chemistry》 SCIE CAS CSCD 北大核心 2008年第12期1475-1486,共12页
The proton transfer isomerization of pyrazole and the water assisting effect by looping 1 to 4 water molecules on the singlet state potential energy surface have been investigated by using hybrid density functional th... The proton transfer isomerization of pyrazole and the water assisting effect by looping 1 to 4 water molecules on the singlet state potential energy surface have been investigated by using hybrid density functional theory method (B3PW91) with a 6-311++G^** basis set. Two mechanisms were proposed to explain the mono- and multi-water assisting effects, respectively. The reactants and products of all groups have been characterized on their potential energy surfaces. For the isomerizafion of monomolecule pyrazole, the isomeriz'ation energy barrier is 46.4 kcal·mol^-1. For the monohydration assisting mechanism, the reactant complex is connected to the product complex via two saddle points. The corresponding isomerization barriers are 46.7and 23.0 kcal·mol^-1, respectively. As to the multihydration assisting mechanism, the isomerization barriers are 12.0, 10.9 and 13.14 kcal·mol^-1 accordingly, when the number of water molecules is 2, 3 and 4, respectively. The multihydration assisting isomerization can occur in water-dominated environments, for example, in the organism, and thereby is crucial to energy transference. The deproton and dehydrogen energies of monomolecule pyrazole and various hydrated pyrazoles were calculated and then found much bigger than the isomerization barriers of their relative complexes, suggesting the impossibility of deprotonation or dehydrogenation. The isomerization of pyrazole is a proton-coupling-electron-migration process, but two different mechanisms are noticed, viz. σ- and π-type mechanisms. The π-bond of pyrazole participates in isomerization in the π-type mechanism, whereas only o-electron takes part in isomerization in the σ-type mechanism. 展开更多
关键词 PYRAZOLE proton transfer σ/π mechanism DFT calculations water-assisting isomerization
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Guanine-regulated proton transfer enhances CO_(2)-to-CH_(4) selectivity over copper electrode
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作者 Jun Gong Jinmeng Li +7 位作者 Chang Liu Fengyuan Wei Jinlong Yin Wenzheng Li Li Xiao Gongwei Wang Juntao Lu Lin Zhuang 《Chinese Journal of Catalysis》 SCIE EI CAS CSCD 2022年第12期3101-3106,共6页
Electrocatalytic CO_(2) reduction has attracted growing attention as a promising route to realize artificial carbon recycling.Proton transfer plays an essential role in CO_(2) reduction and dramatically impacts produc... Electrocatalytic CO_(2) reduction has attracted growing attention as a promising route to realize artificial carbon recycling.Proton transfer plays an essential role in CO_(2) reduction and dramatically impacts product distribution.However,the precise control of proton transfer during CO_(2) reduction remains challenging.In this study,we present a well-controlled proton transfer through the modification of several purines with similar molecular structures,and reveal a direct correlation between surface proton transfer capability and CO_(2) reduction selectivity over Cu electrode.With a moderate proton transfer capability,the guanine modification can remarkably boost CH_(4) production and suppress C2 products formation.In-situ ATR-SEIRAS suggests a weakened^(*)CO intermediate adsorption and a relatively low local pH environment after the guanine modification,which facilitates the^(*)CO protonation and detachment for CH_(4) generation. 展开更多
关键词 CO_(2)electroreduction Surface modification GUANINE proton transfer METHANE Copper
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Ultrafast proton transfer dynamics of 2-(2'-hydroxyphenyl)benzoxazole dye in different solvents
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作者 Simei Sun Song Zhang +4 位作者 Jiao Song Xiaoshan Guo Chao Jiang Jingyu Sun Saiyu Wang 《Chinese Physics B》 SCIE EI CAS CSCD 2022年第2期606-612,共7页
The excited-state intramolecular proton transfer of 2-(2-hydroxyphenyl)benzoxazole dye in different solvents is investigated using ultrafast femtosecond transient absorption spectroscopy combined with quantum chemical... The excited-state intramolecular proton transfer of 2-(2-hydroxyphenyl)benzoxazole dye in different solvents is investigated using ultrafast femtosecond transient absorption spectroscopy combined with quantum chemical calculations.Conformational conversion from the syn-enol configuration to the keto configuration is proposed as the mechanism of excited-state intramolecular proton transfer.The duration of excited-state intramolecular proton transfer is measured to range from 50 fs to 200 fs in different solvents.This time is strongly dependent on the calculated energy gap between the N-S;and T-S;structures in the S;state.Along the proton transfer reaction coordinate,the vibrational relaxation process on the S;state potential surface is observed.The duration of the vibrational relaxation process is determined to be from8.7 ps to 35 ps dependent on the excess vibrational energy. 展开更多
关键词 proton transfer vibrational relaxation femtosecond transient absorption spectroscopy quantum chemical calculations
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Quantum nature of proton transferring across one-dimensional potential fields
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作者 Cheng Bi Quan Chen +1 位作者 Wei Li Yong Yang 《Chinese Physics B》 SCIE EI CAS CSCD 2021年第4期417-424,共8页
Proton transfer plays a key role in the applications of advanced energy materials as well as in the functionalities of biological systems.In this work,based on the transfer matrix method,we study the quantum effects o... Proton transfer plays a key role in the applications of advanced energy materials as well as in the functionalities of biological systems.In this work,based on the transfer matrix method,we study the quantum effects of proton transfer in a series of one-dimensional(1 D) model potentials and numerically calculate the quantum probability of transferring across single and double barriers(wells).In the case of single barriers,when the incident energies of protons are above the barrier height,the quantum oscillations in the transmission coefficients depend on the geometric shape of the barriers.It is found that atomic resonant tunneling(ART) not only presents in the rectangular single well and rectangular double barriers as expected,but also exists in the other types of potential wells and double barriers.For hetero-structured double barriers,there is no resonant tunneling in the classical forbidden zone,i.e.,in the case when the incident energy(E_(i)) is lower than the barrier height(E_(b)).Furthermore,we have provided generalized analysis on the characteristics of transmission coefficients of hetero-structured rectangular double barriers. 展开更多
关键词 proton transfer nuclear quantum effects atomic resonant tunneling double barriers
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Regulation of Excited-State Intramolecular Proton Transfer Process and Photophysical Properties for Benzoxazole Isothiocyanate Fluorescent Dyes by Changing Atomic Electronegativity
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作者 Hongling Zhang Qingtong Liu +2 位作者 Yiying Wang Zhe Tang Panwang Zhou 《Chinese Journal of Chemical Physics》 SCIE EI CAS CSCD 2022年第2期331-337,I0011-I0025,I0003,共23页
Excited-state intramolecular proton transfer(ESIPT)is favored by researchers because of its unique optical properties.However,there are relatively few systematic studies on the effects of changing the electronegativit... Excited-state intramolecular proton transfer(ESIPT)is favored by researchers because of its unique optical properties.However,there are relatively few systematic studies on the effects of changing the electronegativity of atoms on the ESIPT process and photophysical properties.Therefore,we selected a series of benzoxazole isothiocyanate fluorescent dyes(2-HOB,2-HSB,and 2-HSe B)by theoretical methods,and systematically studied the ESIPT process and photophysical properties by changing the electronegativity of chalcogen atoms.The calculated bond angle,bond length,energy gap,and infrared spectrum analysis show that the order of the strength of intramolecular hydrogen bonding of the three molecules is 2-HOB<2-HSB<2-HSe B.Correspondingly,the magnitude of the energy barrier of the potential energy curve is 2-HOB>2-HSB>2-HSe B.In addition,the calculated electronic spectrum shows that as the atomic electronegativity decreases,the emission spectrum has a redshift.Therefore,this work will offer certain theoretical guidance for the synthesis and application of new dyes based on ESIPT properties. 展开更多
关键词 Excited-state intramolecular proton transfer Photophysical properties Energy barrier ELECTRONEGATIVITY
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QM/MM and MD Studies of the First Proton Transfer for O2 Activation in the Catalytic Cycle of Cytochrome P450cin
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作者 LIU Feng-Jiao SONG Jin-Shuai +4 位作者 LU Qian-Qian WEI Jing ZHANG Min-Yi HUANG Jing LI Chun-Sen 《Chinese Journal of Structural Chemistry》 SCIE CAS CSCD 2018年第12期1907-1915,1844,共10页
P450 cin(CYP176 A1) isolated from Citrobacter braakii is a biodegradation enzyme that catalyzes the enantiospecific conversion of 1,8-cineole to(1 R)-6β-hydroxycineole. In many P450 family members the mechanism of pr... P450 cin(CYP176 A1) isolated from Citrobacter braakii is a biodegradation enzyme that catalyzes the enantiospecific conversion of 1,8-cineole to(1 R)-6β-hydroxycineole. In many P450 family members the mechanism of proton delivery for O2activation is proposed to require a conserved acid-alcohol dyad in the active area, while P450 cin has no such residue with alcohol but asparagine instead. In the present work, the mechanism of the first proton transfer of O2activation in P450 cin has been investigated by molecular dynamics(MD) and hybrid quantum mechanics/molecular mechanics(QM/MM) techniques. The MD simulation suggests there are two hydrogen bonding networks around the active site, one involving Asp241 and the other involving Glu356. According to our MD and QM/MM calculations, this Asp241 channel is proposed to be the energy accessible. MD results show that the hydrogen bonds around the substrate may contribute to regio-and stereo-oxidation of the substrate. 展开更多
关键词 P450cin CYP176A1 QM/MM proton transfer
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Effect of Solvent Polarity on Excited-State Double Proton Transfer Process of 1,5-Dihydroxyanthraquinone
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作者 Zheng-Ran Wang Li-Xia Zhu +7 位作者 Xing-Lei Zhang Bo Li Yu-Liang Liu Yong-Feng Wan Qi Li Yu Wan Hang Yin Ying Shi 《Chinese Journal of Chemical Physics》 SCIE EI CAS CSCD 2022年第2期289-294,I0002,共7页
The excited-state double proton transfer(ESDPT)properties of 1,5-dihydroxyanthraquinone(1,5-DHAQ)in various solvents were investigated using femtosecond transient absorption spectroscopy and the DFT/TDDFT method.The s... The excited-state double proton transfer(ESDPT)properties of 1,5-dihydroxyanthraquinone(1,5-DHAQ)in various solvents were investigated using femtosecond transient absorption spectroscopy and the DFT/TDDFT method.The steady-state fluorescence spectra in toluene,tetrahydrofuran(THF)and acetonitrile(ACN)solvents presented that the solvent polarity has an effect on the position of the ESDPT fluorescence emission peak for the 1,5-DHAQ system.Transient absorption spectra show that the increasing polarity of the solvent accelerates the rate of excited state dynamics.Calculated potential energy curves analysis further verified the experimental results.The ESDPT barrier decreases gradually with the increase of solvent polarity from toluene,THF to ACN solvent.It is convinced that the increase of solvent polarity can promote the occurrence of the ESDPT dynamic processes for the 1,5-DHAQ system.This work clarifies the mechanism of the influence of solvent polarity on the ESDPT process of 1,5-DHAQ,which provides novel ideas for design and synthesis of new hydroxyanthraquinone derivatives. 展开更多
关键词 Density functional theory Time-dependent density functional theory Femtosecond transient absorption spectrum Solvent polarity Excited-state double proton transfer Hydroxyanthraquinone compound
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Theoretical investigation on the excited state intramolecular proton transfer in Me_(2)N substituted flavonoid by the time-dependent density functional theory method
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作者 Hang Yin Ying Shi 《Chinese Physics B》 SCIE EI CAS CSCD 2018年第5期534-538,共5页
Time-dependent density functional theory(TDDFT)method is used to investigate the details of the excited state intramolecular proton transfer(ESIPT)process and the mechanism for temperature effect on the Enol^(*)/Keto^... Time-dependent density functional theory(TDDFT)method is used to investigate the details of the excited state intramolecular proton transfer(ESIPT)process and the mechanism for temperature effect on the Enol^(*)/Keto^(*)emission ratio for the Me_(2)N-substited flavonoid(MNF)compound.The geometric structures of the S_(0) and S_(1) states are denoted as the Enol,Enol^(*),and Keto*.In addition,the absorption and fluorescence peaks are also calculated.It is noted that the calculated large Stokes shift is in good agreement with the experimental result.Furthermore,our results confirm that the ESIPT process happens upon photoexcitation,which is distinctly monitored by the formation and disappearance of the characteristic peaks of infrared(IR)spectra involved in the proton transfer and in the potential energy curves.Besides,the calculations of highest occupied molecular orbital(HOMO)and lowest unoccupied molecular orbital(LUMO)reveal that the electronegativity change of proton acceptor due to the intramolecular charge redistribution in the S_(1) state induces the ESIPT.Moreover,the thermodynamic calculation for the MNF shows that the Enol^(*)/Keto^(*)emission ratio decreasing with temperature increasing arises from the barrier lowering of ESIPT. 展开更多
关键词 time-dependent density functional theory excited state intramolecular proton transfer intramolecular charge transfer transition state
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