Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China.
J Phys Chem A. 2013 Apr 11;117(14):2961-70. doi: 10.1021/jp401169p. Epub 2013 Mar 29.
V5O12CH4(+) and V5O13CH4(+) clusters are generated from interactions of pregenerated V5O12(+) and V5O13(+) with CH4 in a fast flow reactor, respectively. The two adsorption complexes are then characterized by collision-induced dissociation (CID) and infrared photodissociation (IRPD) methods. The CID studies indicate that CH4 is molecularly adsorbed on V5O12(+) and V5O13(+). Each of the IRPD spectra of V5O12CH4(+) and V5O13CH4(+) has a broad red band located around 2770 cm(-1) and a narrow blue band located around 2990 cm(-1). The red and blue bands have large and small red shifts with respect to the symmetric and antisymmetric C-H stretch vibrations of free CH4, respectively. Density functional theory calculations are carried out for the structures and vibrational frequencies of V5O12(+) and V5O12CH4(+). The computed results suggest that the anharmonicity including Fermi resonance should be taken into account to interpret the observed IRPD spectrum. In V5O12CH4(+), the CH4 unit adsorbs on the 3-fold coordinated V(5+) site with an η(2) configuration. The stretch of the two C-H bonds close to the V(5+) ion is associated with the red band and the stretch of the other two C-H bonds is associated with the blue band. This study may shed light on the nature of methane adsorption onto vanadium pentoxide surfaces.
V5O12CH4(+)和 V5O13CH4(+) 簇分别通过在快速流动反应器中预先生成的 V5O12(+)和 V5O13(+)与 CH4 的相互作用而产生。然后通过碰撞诱导解离（CID）和红外光解（IRPD）方法对这两个吸附络合物进行了表征。CID 研究表明，CH4 分子吸附在 V5O12(+)和 V5O13(+)上。V5O12CH4(+)和 V5O13CH4(+) 的每一个 IRPD 光谱都有一个位于 2770 cm(-1)左右的宽红外带和一个位于 2990 cm(-1)左右的窄蓝带。红外带和蓝带相对于游离 CH4 的对称和反对称 C-H 伸缩振动都有较大和较小的红移。进行了 V5O12(+)和 V5O12CH4(+)结构和振动频率的密度泛函理论计算。计算结果表明，应考虑非谐性包括费米共振来解释观察到的 IRPD 光谱。在 V5O12CH4(+)中，CH4 单元以 η(2)构型吸附在三配位的 V(5+)位点上。靠近 V(5+)离子的两个 C-H 键的拉伸与红外带有关，而另外两个 C-H 键的拉伸与蓝带有关。这项研究可能有助于了解甲烷在五氧化二钒表面上的吸附性质。
