DFT Study on the Os^＋-catalytic Reduction Reaction of N2O with H2 in the Gas Phase

The Os+-catalytic reduction of N2O by H2 in gas phase has been theoretically investigated with B3LYP method.The reaction mechanisms on the sextet and quartet surfaces were found to be similar.The calculated sextet potential energy profiles show that the two reactions involved in the catalytic cycle,Os+ + N2O → OsO+ + N2 and OsO+ + H2 → Os+ + H2O,have barriers of 28.3 and 123.3 kJ/mol,respectively.In contrast,the reactions on the quartet surfaces are energetically much more favorable.These results rationalize the experimentally observed low catalytic reactivity of sextet(ground-state) Os+.Further,the crossing between the sextet and quartet surfaces are also suggested and qualitatively discussed.     

Theoretical Study on the Mechanism of VO2^＋ ＋ H2 Reaction in the Gas Phase

The mechanism of VO2+ + H2 reaction in the gas phase was investigated by using density functional theory (DFT) at the CCSD//B3LYP/6-311G(2d, p) level. According to our calculation results, the different reaction mechanisms were found for the singlet and triplet potential energy surfaces (PESs). Especially, the crossing points (CPs) among different PESs were located by means of the intrinsic reaction coordinate (IRC) approach presented by Yoshizawa et al., and the structures and energies of the corresponding minimum energy crossing points (MECPs) were obtained by the mathematical algorithm proposed by Harvey et al. Finally, the frontier molecular orbital (FMO) interaction analyses about MECP1 and MECP2 were used to prove our calculation results.     

NOx—Catalyzed Gas—Phase Activation of Methane： the Formation of Hydrogen

NOx-catalyzed oxidation of methane without a solid catalyst was investigated, and a hydrogen selectivity of 27% was obtained with an overall methane conversion of 34% and a free O2 concentration of 1.7% at 700℃.     

Quantum Study on the Hydrogen Bonding Interaction of Luteolin-（CH_3OH）_n

The optimized geometries and vibration frequencies of luteolin,methanol and luteolin-(CH3OH)n complexes have been investigated by density functional theory using B3LYP method.Four stable luteolin-CH3OH complexes,six stable luteolin-(CH3OH)2 complexes and four stable luteolin-(CH3OH)3 complexes have been obtained.The theories of atoms in molecules(AIM) and natural bond orbital(NBO) have been used to analyze the hydrogen bonds of these compounds,and their interaction energies corrected by basis set superposition error are between-8.046 and-76.124 kJ/mol.The calculation results indicate strong hydrogen bonding interactions in the luteolin-(CH3OH)n complexes.Then the nuclear magnetic resonance(NMR) and electronic absorption spectrum of luteolin have been calculated,and the results are in agreement with the experimental data.     

Isomers and [2,3]-Sila-wittig Rearrangement of [（Allyloxy）silyl]lithium Silylenoid in the Gas Phase and THF Solvent

Theoretical calculations of the [2,3]-sila-wittig rearrangement of isomers of [（allyloxy）silyl]lithium （C3H5O）HzSiLi have been performed in the gas phase and THF solvent using the G3MP2B3 method. Seven isomers of silylenoid （C3H5O）H2SiLi, 1-7, are found. The [2,3]-silawittig rearrangement paths are followed using two isomers, 2 and 4, to yield the transition states as well as the products. In the transition state, the silicon center functions as a nucleophile and the aUyl as an electrophile. The interaction between the silicon and allylic sites leads to the formation of SiC（3） bond and the break of O-C（1） bond. Finally, the （allylsilyl）oxylithium （C3H5）H2SiOLi is obtained. The rearrangement paths are confirmed by the intrinsic reaction coordinate （IRC） calculations. The rearrangement mechanisms of reactions of 2 and 4 are similar, and the latter reaction is more favored in the gas phase and THF solvent. Also, the solvent effects are analyzed in this work.     

Theoretical Study of the Reactivity of Mn~+ with CS_2

The reactions of Mn+(7S,5S) with CS2 have been studied at the B3LYP/TZVP level on both septuplet and quintet potential energy surfaces(PESs).The overall energies have been refined at the CCSD(T) level.The calculated results indicate that the reactions of Mn+(7S,5S) with CS2 proceed via an insertion-elimination mechanism.Calculations show that the quintet reaction is more favorable than the septuplet under high energy conditions.The spin-forbidden reaction Mn+(7S) + CS2 → MnS+(5Π) + CS proceeds through a septuplet-quintet surface and the crossing seam is approximately determined.All results have been compared with the existing experimental and theoretical data.     

CO2 Activation by Zr+ and ZrO+ in Gas Phase

The gas-phase reduction of carbon dioxide to carbon monoxide, induced by Zr⁺ and ZrO⁺ catalysts, was investigated at density functional level of theory. Calculations were carried out using both hybrid and pure exchange-correlation functionals in order to reproduce adequately the energetic gap between the Zr^{+ 4}F and ²D electronic states and experimental reaction heats. In agreement with a guided ion beam tandem mass spectrometer study, we have found that carbon dioxide activation by Zr⁺ presents a spin-forbidden mechanism because of a spin inversion process occurring during reaction in the rate- determining step. ZrO⁺ interacts with CO₂ through two possible pathways both endothermic: formation of ZrO ₂ ⁺ and CO products is less unfavourable. Information about ground and excited states of ZrO⁺ and ZrO ₂ ⁺ oxides and bond dissociation energies of species present on the reaction paths was also given.     

气相中Y^＋活化CS2中的C—S键

以Y+与CS2反应作为第二行前过渡金属离子与CS2反应的范例体系.采用密度泛函UB3LYP方法,对于Y+采用Stuttgart赝势基组,对于CS2采用6-311+G(2d)基组,计算研究了Y+离子在基态和激发态时与CS2气相反应的机理.并用UCCSD(T)方法在相同的基组水平上对各驻点作了单点能量校正.结果表明Y+离子与CS2的反应是插入-消去反应,在反应过程中会发生系间窜越,并且找到了两个势能面的能量最低交义点.     

水催化HBrO与OH自由基反应的微观机理

采用密度泛函理论,分别在B3LYP/6-311++g(d,p)和B3LYP/aug-cc-PVTZ理论水平下,系统研究了无水和水催化的OH自由基与HBrO反应,即HBrO+OH和HBrO+OH+H_2O 2个反应的微观反应机理,给出了所有可能发生的反应路径,并指出能量最低的反应通道.对于没有水参与的反应,由于OH自由基进攻HBrO方式不同,存在顺式方向和反式方向2种进攻方式的反应路径;当有一分子水参与反应时,考虑HBrO H_2O复合物与OH自由基的反应和HBrO与H_2O OH复合物2种反应情况,共发现4条不同的反应路径.这2种反应的所有路径均是在OH自由基提取氢之前以氢键复合物形式存在,反应过程均为无势垒加合过程,总反应为放热反应.水对目标反应起催化作用,有效地降低了反应的势垒,可以加快OH自由基和HBrO的消耗速度.     

气相中2Sr+和2Ba+催化N2O与CO还原反应的理论研究

用密度泛函理论DFT-UB3LYP方法,对2Sr+,2Ba+采用相对论校正赝势基组SDD,对C,N,O采用6-311+G(2d)基组,计算研究了气相中碱土金属离子2Sr+,2Ba+催化N2O(X1∑+)+CI(X1∑+)→N2(X1∑+g)+CO2(X1∑+g)反应的微观机理.优化了二重态势能面上各反应物、中间体和过渡...     

HS和HONO反应机理的研究

采用密度泛函和耦合簇理论方法研究了HS与HONO的反应机理.在B3LYP/6-311+G(2df,2p)水平上对HS+HONO反应中的所有物种进行了几何构型优化和频率分析,通过内禀反应坐标(IRC)确认了反应物、过渡态、中间体和产物之间的相关性;采用CCSD(T)/6-311+G(2df,2p)方法获得了各物种的单点能.计算结果表明:HS+HONO的主要反应通道为HS+cis-HONO→p2-cis-IM1→p2-cis-TS→p2-IM2→P2(H_2S+NO_2),其反应活化能为71.26kJ·mol~(-1).     

La+活化NH3的自旋禁阻反应机理

采用密度泛函理论的UB3LYP方法,计算研究了气相中La+活化NH3的两态反应机理。为了理解由La+活化NH3过程中自旋翻转行为,对自旋态分别为单重态和三重态两个反应势能面进行了计算研究,其结果表明,La+活化NH3的过程是通过自旋态势能面交叉产生的自旋禁阻反应,单、三重态势能面最低能量交叉点(MECP)附近的系间窜越导致H向La+转移和脱H2反应能垒的降低。此外,运用自然键轨道(NBO)布居分析,研究了反应中各个物种的成键特性。所确定的最低能量反应路径为:3La++NH3→3IM1→MECP→1TS12→1IM2→1TS23→1IM3→1LaNH++H2。     

H+NH3反应势能面的量子化学研究

本文采用UCCSD(T)/aug-cc-pVTZ方法研究了H NH3反应势能面,获得了夺氢反应和交换反应过渡态的的几何结构和振动频率。夺氢反应的过渡态具有Cs对称性,其能垒为61.92 kJ/mol。交换反应的过渡态具有C3v对称性,其能垒为39.69 kJ/mol。H NH3发生形成Td对称性的反应中间体NH4里德堡自由基。与夺氢反应相比,交换反应具有更低的反应能垒,并且NH4自由基在反应中可形成长寿命的共振态,和夺氢反应形成竞争关系,因此在H NH3反应的量子动力学研究中必须同时考虑这两类反应。本文还采用更大的基组aug-cc-pVQZ和aug-cc-pV5Z研究了势能面对基组的收敛行为。     

Theoretical investigations of spin-orbit coupling and intersystem crossing in reaction carbon dioxide activated by [Re(CO)2]+

In order to further explore the detailed reaction mechanism of carbon dioxide activated by [Re(CO)₂]⁺ complex, CCSD(T) methods was performed to determine related potential energy surface (PES). Crossing point is determined by using a partially optimized method. The result shows that larger spin-orbital coupling (155.37 cm⁻¹) and intersystem crossing probabilities in spin-forbidden region causes the electron to spin flip at the minimum energy crossing point and access to the lower singlet PES. Nonadiabatic rate constant k is estimated to be quite rapid, so transition state (¹TS1) is rate-controlled steps. In addition, the electronic structure of oxygen-atom transfer process is further analyzed by localized molecular orbital and Mayer bond order. The analysis finds that the form of main bonding orbital is the electron contribution from the p(O) in CO₂ to the empty d(Re) orbital.     

DFT Study of N_2O Activation with La~+, Hf~+, Ta~+ and W~+ in the Gas Phase

The spin‐forbidden reaction N₂O(X¹Δ)+M⁺→N₂ (X¹ Σ ⁺_g)+MO⁺(M⁺=La⁺, Hf⁺, Ta⁺, W⁺) was discussed using density functional theory. The reaction mechanism between M⁺ transition metal ions and N₂O is an insertion‐elimination one. All products are formed in exothermic processes. The potential energy curve crossings, which dramatically affect reaction mechanisms, were discussed in detail. In comparison with the previous work, an essential conclusion could be drawn that the reaction N₂O(X¹Δ)+CO(¹Δ⁺)→N₂(X¹ Σ ⁺_g)+CO₂(¹ Σ ⁺_g) catalyzed by M⁺ was endothermic by 358.89 kJ·mol^?1 which is in accord with the experiment finding.