采用密度泛函理论(DFT)B3LYP与CCSD方法研究了二重态和四重态势能面自旋禁阻反应VO(∑ + )活化CH 3 OH( 1 A′)分子C-H, O-H键的微观机理. 通过自旋-轨道耦合的计算讨论了势能面交叉点和可能的自旋翻转过程. 在MECP处, 四重态和二重态间的旋轨耦合常数为131.14 cm -1 . 自旋多重度发生改变, 从四重态系间穿越到二重态势能面形成中间体 2 IM1, 导致反应势能面的势垒明显降低.

The different potential energy surfaces (PESs) of Ni+ (2D, 3d9) with butanone in gas phase have been systematically explored by density functional theory (DFT). Two parallel decomposition reaction mechanisms have been identified. The course that the Ni+ inserts into the σ-bond of the C C2H5 or C CH3 leading to the C C bond activation has been analyzed using the natural bond orbital (NBO). Finally, the conclusion of the theory calculation was consistent with the experimental results which provided by the Darrin J. Bellert group in 2011 that three neutral organic molecule products (ethylene, acetaldehyde and methane) were obtained.

The mechanism of the spin-forbidden reaction VO (∑+) + CH3OH (1A′) on quartet and doublet potential energy surfaces (PESs) has been investigated by DFT of B3LYP and CCSD. Crossing points between the different potential energy surfaces and the possible spin inversion process are discussed by spin-orbit coupling (SOC) calculations. The values of the SOC constants at MECP are 131.14 cm-1 between quartet and doublet PESs. The intersystem crossing (ISC) between different quartet and doublet PESs would occur and has been produced 2IM1, which obviously reduce energy barriers.

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.

The insertion reaction of Ce+(4H, 4f15d2) into the NH bond of ammonia on the doublet and quartet potential energy surfaces has been investigated at the density functional theory using the hybrid exchange correlation functional B3LYP level. Crossing points between the potential energy surfaces are located using different methods, and possible spin inversion processes are discussed by means of spin–orbit coupling (SOC) calculations. As a result, there is a crossing point between the doublet and the quartet state surfaces. The reacting system will start in the quartet ground state, the change of the spin state probably occurring immediately after the formation of the electrostatic complex intermediate, leading to a significant decrease in the barrier height of 4TS12 from 17.3 to 2.5kcal/mol, and then move on the doublet potential energy surface as the reaction proceeds. The minimum energy crossing point (2/4MECP) is located by using the methods of Harvey et al. On the basis of the calculated SOC value and potential energy surfaces, the estimated probability of ISC (PISC) at 2/4MECP is approximate 0.214. Additionally, the natural bond orbital (NBO) and natural resonance theory (NRT) analyses have been used to characterize the nature of the bonds for all of the minima and transition states along the optimal reaction paths. On the basis of the obtained results, it is possible to conclude that for the molecules considered the reaction is a spin-forbidden process, this is a typical two-state reactivity (TSR) reaction. These conclusions are consistent with the experimental observations.

The mechanisms of the reactions between N(2)O and CO catalyzed by IrO(n)(+) (n = 1, 2) have been investigated using B3LYP and CCSD(T) levels of theory. Spin inversion among three reaction profiles corresponding to the quintet, triplet, and singlet multiplicities was discussed by using spin-orbit coupling (SOC) calculations. The probability of electron hopping in the vicinity of the (MECP) has been calculated by the Landau-Zener-type model. The single P(1)(ISC) and double P(2)(ISC) passes estimated at MECP1(#) (SOC = 198.61 cm(-1)) are approximately 0.11 and 0.20, respectively. Important analysis and explanations were done using molecular orbital theory and natural bonding orbital (NBO). The energetic span (δE) model coined by Kozuch was applied in this cycle. The turnover frequency (TOF)-determining transition state (TDTS) and TDI (TOF-determining intermediate) were confirmed. Finally, TOF(IrO(+))/TOF(IrO(2)(+)) = 0.38 at 298 K.