La^+活化NH_3的自旋禁阻反应机理  

Spin-Forbidden Reaction Mechanism of NH_3 Activated by La^+ in Gas Phase

作　　者：刘玲玲[1] 赵国虎[1] 张力[1] 饶红红[1] 杨彩玲[1] 王永成[2] 

机构地区：[1]兰州城市学院化学与环境科学学院,兰州730070 [2]西北师范大学化学化工学院,兰州730070

出　　处：《化学通报》2012年第4期318-323,共6页Chemistry

基　　金：国家自然科学基金项目(20873102);甘肃省科技厅自然科学基金项目(096RJZA064)资助

摘　　要：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。Gas-phase ammonia activation mechanism by La^＋ was studied at the density functional level of theory using the hybrid exchange correlation functional B3LYP.Two reaction potential energy surfaces（PESs） corresponding to the triplet and singlet multiplicities were investigated calculationally in order to understand the process of some spin inversion during ammonia activation.The results showed that ammonia activation mediated by La^＋ is a typical spin-forbidden process resulting from the crossing among the multistate PESs.The minimum energy crossing point（MECP） lead to decrease in the barrier heights of TS12 that correspond to the first hydrogen transfer and the reductive elimination step of H2,respectively.We also made use of the natural bond orbital（NBO） theory to characterize the bonding characters between different groups for some important species involved.The minimum energy pathway can be described as 3La^＋＋NH3→^3IM1→MECP→^1TS12→^1IM2→^1TS23→^1IM3→^1LaNH＋＋H2.

关 键 词：La^+活化NH_3 密度泛函方法 自旋禁阻反应 最低能量交叉点 系间窜越 

分 类 号：O643.12[理学—物理化学]