CH4 Activation by W Atom in the Gas Phase: A Case of Two-State Reactivity Process

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• 作者：YongCheng Wang ; Qiang Wang ; ZhiYuan Geng ; LingLing Lv ; YuBing Si ; QingYun Wang ; HuiWen Liu ; DanDan Cui
• 刊名：Journal of Physical Chemistry A
• 出版年：2009
• 出版时间：December 10, 2009
• 年：2009
• 卷：113
• 期：49
• 页码：13808-13815
• 全文大小：276K
• 年卷期：v.113,no.49(December 10, 2009)
• ISSN：1520-5215

文摘

Gas-phase methane activation by tungsten (W) atoms was studied at the density functional level of theory using the hybrid exchange correlation functional B3LYP. Four reaction profiles corresponding to the septet, quintet, triplet, and singlet multiplicities were investigated in order to ascertain the presence of some spin inversion during the methane activation. Methane activation mediated by W atoms was found to be a spin-forbidden process resulting from the crossing among the multistate energetic profiles. On the basis of the Hammond postulate, this is a typical two-state reactivity (TSR) reaction. The minimum energy crossing points lead to decrease in the barrier heights of TS01, TS12, TS23, and TS24 that correspond to the first, second, and third hydrogen transfer and the reductive elimination step of H₂, respectively. The spin−orbit coupling is calculated between electronic states of different multiplicities at the crossing points (MECPs) to estimate the intersystem crossing probabilities, and the probability of hopping from one surface to the other in the vicinity of the crossing region is calculated by the Landau−Zener type model.