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A systematic investigation on the SN2 displacement reactions of nine carbene radical anions toward the substrate CH3Cl has been theoretically carried out using the popular density functional theory functional BHandHLYP level with different basis sets 6-31+G (d, p)/relativistic effective core potential (RECP), 6-311++G (d, p)/RECP, and aug-cc-pVTZ/RECP. The studied models are CX1X2•− + CH3Cl → X2X1CH3C• + Cl−, with CX1X2•− = CH2•−, CHF•−, CHCl•−, CHBr•−, CHI•−, CF2•−, CCl2•−, CBr2•−, and CI2•−. The main results are proposed as follows: (a) Based on natural bond orbital (NBO), proton affinity (PA), and ionization energy (IE) analysis, reactant CH2•− should be a strongest base among the anion-containing species (CX1X2•−) and so more favorable nucleophile. (b) Regardless of frontside attacking pathway or backside one, the SN2 reaction starts at an identical precomplex whose formation with no barrier. (c) The back-SN2 pathway is much more preferred than the front-SN2 one in terms of the energy gaps [Δ E [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: A computational study of the [2+2] cycloaddition reaction pathways for formaldehyde–ketene and formaldehyde–isocyanic acid has been presented by using the DFT(B3LYP) method. These cycloaddition reactions could yield to eight different four-membered molecules. In the two considered reactions, the reactions for the β-propiolactone and oxazetidinone products have the lower barriers of 26.40 and 32.88kcalmol−1 and are exothermic by 27.68 and 4.00kcalmol−1, respectively. The β-propiolactone and oxazetidinone ring compounds have been predicted to be the most stable thermodynamically. Simulation of the solvent environment (toluene, THF, acetone, acetonitrile and water) has been investigated by using polarized continuum model method, yet only small differences have been found to occur in energetics between the studied structures in the gas-phase and in the solvent. [Copyright &y& Elsevier]

Abstract: A theoretical investigation at DFT (B3LYP) level on the cyclopropanation reactions catalyzed by nickel(0) and nickel(II) have been extensively investigated. The computation results show that the active catalytic species formed by a CH2 fragment and the Cl2Ni(PH3)2 is carbenoids (PH3)2Ni(CH2Cl)Cl (IMA) and (PH3)Ni(CH2PH3)Cl2 (IMB), but both the carbenes (Cl2NiCH2 (IMC), (PH3)3NiCH2 (IME) and (PH3)2NiCH2 (IMG)) and carbenoids (ClNiCH2Cl (IMD), Ni(CH2PH3)(PH3)2 (IMF) and Ni(CH2PH3)PH3 (IMH)) are active catalytic species obtained from NiCl2, Ni(PH3)3, Ni(PH3)2 and a CH2 fragment. The cyclopropanation reaction proceeds through either concerted or multistep reaction pathway. The most favor cyclopropanation reactions catalyzed by nickel(II) is multistep pathway for IMD with a barrier of 21.65kcalmol−1 but is endothermic 6.74kcalmol−1, and the most favor nickel(0) catalyzed cyclopropanation reactions is also multistep pathway for IME, IMH and IMG species all with barriers of 21.93kcalmol−1 but the downhill potential energy surface discloses that each step of the cyclopropanation reaction are all irreversible. Thus, nickel(0) catalyzed cyclopropanation reaction proceed easer than nickel(II). [Copyright &y& Elsevier]

Abstract: The cyclopropanation reaction of ethene with aluminum carbenoid has been studied by means of the B3LYP hybrid density functional method. The reaction goes through two pathways: methylene transfer and carbometalation. In methylene transfer pathway, a quantum-chemical investigation shows that the reactions of the carbenoids X2AlCH2X 1-X, (X=F, Cl, Br, I) with ethene 2 to cyclopropane 3+lX3 profit from a weakening of the C–X bonds by the C–Al bonds in the carbenoids 1-X and in the complex [1-X∗2]. The C–F bond is more affected than the C–I bond. Since in the transition states 3[1-X∗2]‡ AlHal is strongly decomplexed, the cleavage of the C–Hal bond is essential compensated by the formation of the Al–Hal bonds, which leads to almost equal transition state energy for the reactions of 1-X with 2. In contrast with methylene transfer, the cyclopropanation reaction of the carbometalation pathway profit from a weakening of the C–Al bonds by the C–X bonds. [Copyright &y& Elsevier]

Abstract: Six indoline-based dyes 1–6 used in DSSCs with difference in π spacer were theoretically researched and verified using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) to shed light on how the additional (auxiliary) acceptor and π spacer order influence the performance of the dye. Key parameters associate with the short-circuit current density (J sc) and open-circuit photovoltage (V oc), including light-harvesting efficiency LHE, electron injection driving force ΔG inject, total reorganization energy λ total (λ h and λ e), the vertical dipole moment μ normal, the energy differences eV oc between E LUMO and E CB as well as the extent of electron recombination were characterized. The theoretical results reveal that compared with dye 1, dyes 2–6 improve the performance potentially due to their auxiliary acceptor. These enable us to determine these factors related to the J sc and V oc can be significantly influenced by the incorporated electron-withdrawing subunit into molecular backbone. [Copyright &y& Elsevier]

Abstract: The spin-forbidden reaction mechanism of Ir+ with CH3F to yield H2 or HF has been investigated using density functional theory (DFT) calculations. The overall H2 elimination reaction is calculated to be exothermic, by 36.3 kcal/mol. One pathway is found on three potential energy surfaces (PESs), whereas the HF-elimination reaction is exothermic by 32.8 kcal/mol, two reaction pathways are identified on the quintet and triplet surfaces, only one reaction pathway is identified on the singlet surface. The reaction mechanism can be explained by the simple donor–acceptor model. According to the revealed mechanism and the calculated potential energy surfaces, H2-elimination is energetically much more favorable than HF-elimination. These conclusions are consistent with the experimental observations. [Copyright &y& Elsevier]

Abstract: The gas-phase reactions of fluorocarbon compounds CH4– n F n (n =1–3) with Pt (3D, 1S) have been systematically explored via density functional theory (DFT) in order to investigate the mechanisms of these reactions. The results indicate that a reaction of CH3F with Pt (3D, 1S) experiences a rearrangement process to generate counterintuitive production (CH2F−PtH). CH2F2 and CHF3 activation by Pt (3D, 1S) yields high-oxidation-state complexes with carbon–metal double bonds. Moreover, the attack of platinum atoms on fluorine atoms in different fluorocarbon compounds involves intersystem crossing (ISC) between triplet and singlet state Potential Energy Surfaces (PESs). The crossing points (CPs) have been located by the intrinsic reaction coordinate (IRC) approach used by Yoshizawa et al. and corresponding minimum energy crossing points (MECPs) obtained by the mathematical algorithm proposed by Harvey et al. have also been used. Additionally, possible spin inversion processes are discussed using spin–orbit coupling (SOC) calculations. [ABSTRACT FROM AUTHOR]

Abstract: The mechanisms of the reaction between N2O and CO catalyzed by MO+ (M=Ru, Os) have been investigated using the density functional theory (DFT). The potential energy surfaces, 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 results indicate the reactions are O-atom abstraction mechanism for the catalysts RuO+ and OsO+. The large probability value shows the intersystem crossing occurs efficiently, which makes the reaction access to a lower energy pathway and accelerate the reaction rate. [ABSTRACT FROM AUTHOR]

Abstract: Activation of the N–N and N–O bonds by La+ in nitrous oxide has been examined systematically using both DFT and CCSD(T) methods. The calculated results indicate that the reaction of La+ (3F, 1D) with N2O (X 1∑) including several reaction pathways and numerous isomers, leads to oxidation, LaO+ (1∑, 3Δ)+N2 () or nitration, LaN+ (2∑+, 4∑+)+NO (X 1∏). The attack of the La+ on the O-end of N2O involves intersystem crossing (ISC) between singlet and triplet state potential-energy surfaces (PESs). Thus, possible spin-inversion process is discussed by means of spin–orbit coupling (SOC) calculations. The probability values of the single () and double () passes are estimated at MECP are approximately 6.682×10−2 and 0.125, respectively. The calculated results also revealed that the O-transfer reaction is energetically more favorable than the N-transfer reaction on the both spin state PESs. These results are in good agreement with experimental observations. [Copyright &y& Elsevier]

Abstract: Calculations based on density functional theory (DFT) have been carried out to investigate the multi-centered transition state (MCTS) reaction mechanisms associated with the gas-phase ion/molecule reaction of YNH+ with ethene. The potential energy surfaces (PESs), including both reaction pathways of hydrogen and ammonia elimination, have been explored and characterized. By contrast with ammonia elimination, dehydrogenation reaction channel is energetically favorable, which is in good agreement with the experimental observation. Moreover, the dominating product (YC2H3N+) can further react with ethene and the corresponding reaction mechanism which proceeds in a two-step manner and leads to the six-membered metallacyclic structure YC4H5N+, has also been investigated. [Copyright &y& Elsevier]

Abstract: Calculations based on density functional theory (DFT) have been carried out to investigate geometries and bonding characteristics of all the stationary points associated with the gas-phase ion/molecule reactions of YNH+ (1∑+) with propene. The potential energy surface (PES), including six reaction pathways (four dehydrogenation and two demethanation processes), has been explored and analyzed. By contrast, dehydrogenation reaction channels that are associated with two consecutive hydrogen transfers from C atoms of propene fragment to Y atom of YNH+ moiety and then elimination of H2, are energetically favorable, which is in good agreement with the experimental observation. [Copyright &y& Elsevier]

Abstract: The gas-phase reaction of activation of C–C double bond of C2H4 by has been investigated using density functional theory (DFT) at the UB3LYP/6-311G(2d,p) level. The calculation results show that the reaction experiences rearranged process. On the basis of Hammond postulate, this is a typical ‘two-state reactivity’ (TSR) reaction. The involving crossing between the singlet and triplet potential energy surfaces has been discussed by means of the intrinsic reaction coordinate (IRC) approach used by Yoshizawa et al., and a minimum energy crossing point (MECP) that we obtained by the mathematical algorithm proposed by Harvey et al. has been also employed. [Copyright &y& Elsevier]

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 pathway and energies for the gas-phase CO2–CO conversion by W+ are discussed from density functional theory (DFT) UB3LYP calculation at the relativistic effective core potential (ECP) of Stuttgart basis sets with W+ and 6-311+G(2d) with CO2. The reaction mechanism between W+ and CO2 is an insertion–elimination mechanism. The W+ inserts with no energy barrier into a CO bond resulting in an OWCO+ insertion product. The intrinsic reaction coordinate for the insertion process has been defined and the reaction mechanism has been investigated by analyzing various structures along this path. Crossing points (CPs) are localized, and possible spin inversion processes are discussed by means of the intrinsic reaction coordinate (IRC) approach. [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 entire reaction mechanism for the gas-phase CO2–CO conversion by early transition metal ions, La+, Hf+, and Ta+, are studied using density functional theory (DFT). The results indicate that the lowest energy path corresponds to the η2-O coordination of CO2 followed by the insertion of M+ into the C–O bond. The reactions are all exothermic due to the participation of the metal ions, to be compared with the strong endothermic process of the unimolecular CO2 decomposition. Crossing points (CPs) are localized, and possible spin inversion processes are discussed by means of the intrinsic reaction coordinate (IRC) approach. [Copyright &y& Elsevier]

Abstract: The gas-phase reaction of activation C CH3OCH3 by Ti+ has been investigated using density functional theory (DFT) at the 6-311++G(3df,3pd)//6-311+G(d) level. The structures of all reactants, intermediates, transition structures and products of this reaction have been optimized and characterized at the quartet and doublet electronic states. Crossing points (CPs) are localized, and the possible spin inversion processes are discussed by means of the intrinsic reaction coordinate (IRC) approach. Finally, two competitive reaction pathways, including the CP, are proposed from the most stable reactants to the most thermodynamically stable products. [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 mechanisms for the abstraction reactions of germylenes with oxirane and thiirane have been characterized in detail using density functional theory. All the stationary points were determined at the B3LYP/6-311++G (d, p) level of the theory. As a result, our theoretical investigations suggest that, irrespective of deoxygenation and desulfurization, the alkyl-substituted germylene abstractions are much more favorable than those of the π-donor-substituted germylenes. Moreover, for a given germylene, the desulfurization reaction is more exothermic as well as more kinetically favorable. Furthermore, a configuration mixing model based on the work of Pross and Shaik is used to rationalize the computational results. A comparison with carbene and silylene also led to the same result and the results obtained allowed a number of predictions to be made. [Copyright &y& Elsevier]