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Abstract: Activation of the C–H bonds in C2H4 by the group 5 metal atoms have been examined systematically using density function theory (DFT, UB3LYP) with the relativistic effective core potential (ECP) of basis sets (SDD) for V, Nb, Ta and the 6-311++G (3df, 3pd) basis set for C and H. The reaction mechanisms have been explored in detail on sextet, quartet and doublet potential energy surfaces. The process involves an intersystem crossing (ISC) between the quartet and doublet state. We have obtained many minimum energy crossing points (MECPs) using the algorithm in Harvey method. These theoretical results can act as a guide to further theoretical and experimental researches. [ABSTRACT FROM AUTHOR]

Abstract: The gas-phase Fe+-mediated cycle reaction N2O (1Σ+)+NH3 (1A1)+O2 →N2 +H2O (1A1)+ cis-HNO2 (1A′) on both sextet and quartet potential energy surfaces (PESs) has been theoretically investigated using density functional theory. Spin inversion between sextet and quartet potential energy surfaces was discussed by using spin–orbit coupling (SOC) calculations. The crossing points and the corresponding minimum energy crossing points have been explored. The probability of hopping in the vicinity of the crossing has been calculated by the Landau–Zener-type model. The energetic span (δE) model has been applied in this cycle to obtain some kinetic information. TOF (E-representation) was calculated at different temperatures. TDTS (TOF-determining transition state) and TDI (TOF-determining intermediate) were confirmed. Finally, the minimum energy reaction path was found. [ABSTRACT FROM AUTHOR]

A systematic investigation on the H‐abstraction reactions of 8 carbene radical anions with CCl3H has been performed theoretically using the popular DFT functional BHandHLYP/aug‐cc‐pVTZ/RECP level of theory. As a result, our studies strongly suggest that the reactivity of the title reactions (CX1X2•− + CCl3H) present increase in the order: CHI•− < CHBr•− < CHCl•− < CHF•− for first halogen CHX•− and CCI2•− < CBr2•− < CCl2•− < CF2•− for second halogen CX2•−, more important, the reactions of the former exhibit more activity than those of corresponding the latter. Moreover, based on the NBO analysis, the Activation Strain model analysis and the correlations analyses of activation barrier with both PA and IE, respectively, we further confirm over the conclusion. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 [ABSTRACT FROM AUTHOR]

Abstract: The two-state reaction mechanism of PtO+ with N2O and CO on the quartet and doublet potential energy surfaces has been investigated at the B3LYP level. The computation results reveal that the reaction is an O-atom abstraction mechanism. Crossing points (CPs) between the potential energy surfaces (PESs) are located, and possible spin inversion processes are discussed by means of spin–orbit coupling (SOC) calculations. The probability of hopping in the vicinity of the crossing has been calculated by the Landau–Zener-type model. The probability value shows the intersystem crossing occurs efficiently, which makes the reaction access to a lower energy pathway and accelerate the reaction rate. [Copyright &y& Elsevier]

The mechanisms of the reaction of lanthanide ions (Ce and Pr) with the carbon dioxide were investigated at the B3LYP level of theory. The crossing points (CPs) between the different potential energy surfaces (PESs) have been located by means of the intrinsic reaction coordinate approach used by Yoshizawa et al., and corresponding minimum energy crossing points (MECPs) that we obtained by the mathematical algorithm proposed by Harvey et al. has also been used. In addition, possible spin inversion processes are discussed by means of spin-orbit coupling (SOC) calculations. The value of 61.68 cm (for MECP) and 69.17 cm (for MECP) for the SOC constants indicates that the spin crossing process in Ln + CO (∑) reaction can be occurred efficiently because of the large SOC involved. And the O-atom affinities (OA) testified that the argumentation is thermodynamically allowed. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 [ABSTRACT FROM AUTHOR]

Abstract: Ab initio calculations of the two title reactions have been made to compare reactivities of OCS and CS2 toward a nucleophile, . MP2/6-311++G(d, p) geometry optimizations on the singlet potential energy surface have demonstrated that respective channels start from key intermediates and have revealed that multistep paths give the most favorable products: (1) +OCS→H2NS− +CO; (2) +OCS→HS− +HNCO; (3) +OCS→NCS− +H2O; (4) +OCS→NCO− +H2S; (5) +CS2 →NCS− +H2S; (6) +CS2 →HS− +HNCS. Furthermore, to get more reliable energetic data, single-point calculations are carried out at CCSD/6-311++G(d, p) level. The calculated result is consistent with the measured large rate constant in experiment. A comparison of reaction mechanisms is offered between +OCS and +CS2. [ABSTRACT FROM AUTHOR]

Abstract: The entire reaction mechanism for the gas phase CO–CO2 conversion by FeO+ is discussed by means of the density functional theory and the intrinsic reaction coordinate approach. The calculated results have strongly indicated that the reaction of is a spin-forbidden reaction between the quartet and the sextet potential energy surfaces (PESs). There is a crossing point between the quartet and the sextet potential energy surfaces which may play a significant role in this reaction, by which the activation energy can be decreased from −15.1 to −56.4kJmol−1 at the reaction system. [Copyright &y& Elsevier]

Abstract: The reaction of Lu+ with CH3F, which was selected as a representative system of the activation of C–F bond in fluorohydrocarbons by late lanthanide cations, has been examined using density functional theory (DFT). The potential energy surfaces (PESs) of [Lu, C, H3, F]+ were explored in detail in both singlet and triplet electronic states. The electron-transfer reactivity of the reaction was analyzed using the two-state model, and a strongly avoided crossing behaviour on the transition state (TS) area was shown. The theoretical results can act as a guide to further theoretical and experimental researches. [Copyright &y& Elsevier]

Abstract: The reaction of La+ with CH3F, which was selected as a representative system of the activation of C–F bond in fluorohydrocarbons by bare lanthanide cations, has been examined using density functional theory (DFT) to explore more integrated reaction pathways and mechanisms on both singlet and triplet potential energy surfaces (PESs). A direct fluorine abstraction mechanism and an insertion–elimination mechanism were revealed, the related thermochemistry data involved in reaction of La++CH3F were determined. The crossing points (CPs) have been found by means of single-point computations as a function of the structural change along the intrinsic reaction coordinate (IRC) in this manuscript. The present results not only support the existing reaction conclusions inferred from early experimental data, but also complement the pathway and mechanism for this reaction, which can act as a guide for further experimental researches and theoretical investigations. [Copyright &y& Elsevier]

Abstract: The gas-phase reaction of activation Cbond of C2H4 by has been investigated using density functional theory (DFT) at the UB3LYP/6-311++G (3df,3pd)//6-311G(2d,p) level. The calculation results show that the reaction experiences a rearranged process. On the basis of Hammond postulate, this is a typical ‘two-state reactivity’ (TSR) reaction. The involving crossing between the potential energy surfaces is discussed by means of the intrinsic reaction coordinate (IRC) approach used by Yoshizawa et al., and a crossing point (CP) is located. In addition, the orbital interaction analysis of activation C carried out by fragment molecular orbital (FMO), and compared with the DCD model. [Copyright &y& Elsevier]

Abstract: The reactivity of X(3P) (X=Ge, Sn, Pb) with N2O(X1Σ) on both singlet and triplet potential energy surfaces have been investigated at the B3LYP level of theory. To accurately evaluate the activation barrier and reaction energy, the coupled cluster single point calculations using the B3LYP structures is performed. The calculated results are in good agreement with experimental observations. The (X=Ge, Sn, and Pb) reactions that Arthur Fontijn has been observed are spin-forbidden for formation of ground state products in the experiments. The present paper is discussed with the aid of the direct abstraction (DA) mechanism (also called the surface crossing model), a correlation argument based on separated fragments X+O+N2 can explain the inefficiency of the (X=Ge, Sn, and Pb) reactions at 298K by the need to switch electron configurations along low-energy adiabatic paths from ground-state reactants to energetically accessible product states. [Copyright &y& Elsevier]

Abstract: The reactivity of Cu+ with OCS on both singlet and triplet potential energy surfaces (PES) has been investigated at the UB3LYP/6-311+G(d) level. The object of this investigation was the elucidation of the reaction mechanism. The calculated results indicated that both the C–S and C–O bond activations proceed via an insertion–elimination mechanism. Intersystem crossing between the singlet and triplet surfaces may occur along both the C–S and C–O bond activation branches. The ground states of CuS+ and CuO+ were found to be triplets, whereas CuCO+ and CuCS+ have singlet ground states. The C–S bond activation is energetically much more favorable than the C–O bond activation. All theoretical results are in line with early experiments. [Copyright &y& Elsevier]

Abstract: The mechanism of the spin-forbidden reaction Ti+(4F)+N2O(X 1Σ)→TiO+(2Δ)+N2(X 1Σg +) on both doublet and quartet potential energy surfaces has been investigated at the B3LYP level of theory. Crossing seam between the potential energy surfaces and possible spin inversion process are discussed by means of the intrinsic reaction coordinate (IRC) approach. To emphasize the importance of charge transfer, the Ti+ ionic and O atomic charges with orbital NBO populations along the quartet IRC path are calculated. The calculated results indicated there is one crossing seam between the doublet and quartet potential energy surfaces, and spin inversion should occur in the exit channel. But it occurs only near the transition state 4Ti+–TS. The activation energy from Ti+(4F) to TiO+(2Δ) via 4Ti+–TS is calculated to be 1.43kcal/mol. And due to the charge transfer N2O molecule becomes bent, which is a favorable process for the title reaction. Therefore, the reaction efficiency is most likely to be determined by the activation energy from Ti+(4F) to TiO+(2Δ) via 4Ti+–TS. These results are in good agreement with experimental observations. [Copyright &y& Elsevier]

Abstract: The mechanism of the spin–forbidden reaction on both doublet and quartet potential energy surfaces has been investigated at B3LYP, CCSD(T) and CASSCF levels of theory. The minimum energy point (MEX-1) on the doublet–quartet crossing surface is determined using the complete-active-space-self-consistent field (CASSCF) calculations with (3,4), (5,5), (7,6), and (7,7) active spaces with a weighting of 50%/50% to the doublet and quartet states. The minimum energy point (MEX-1) has a Cs structure resembling the intermediate structure 2M-1. The intersystem crossing at the MEX-1 crossing point is taking place, and it is attributed to the stronger spin–orbit coupling (SOC)(50.2–75.5cm−1) and the barrier (65.01–72.10kJ/mol) with respect to the ground state reactants . This is in close agreement with the experimental observation reporting large rate coefficients. [Copyright &y& Elsevier]