Belykh Roman, Maevskaya Maria, Krauklis Irina, Tsyganenko Alexey
Department of Physics, Saint-Petersburg State University, 1 Ulianovskaya Str., Peterhof, Saint-Petersburg 199034, Russia.
J Phys Chem A. 2015 Mar 19;119(11):2363-70. doi: 10.1021/jp507394s. Epub 2014 Sep 29.
Variable-temperature FTIR spectra of CO adsorbed on NaCl and KBr films are shown to reveal linkage isomerism, that is, formation of C- and O-bonded adsorption complexes with the same cationic sites. Not all of the sites can be involved in that, only the three- or four-coordinated cations located on kinks, edges, or steps of microcrystals. For NaCl, these adsorption complexes account for the high-frequency (HF) C-O stretching bands at 2175 and 2160 cm(-1). Coresponding LF bands of O-bonded CO were found at 2115 and 2124 cm(-1). In the spectrum of KBr, the HF band is poorly resolved, and only one LF band can be clearly seen, near 2124 cm(-1). The value of the isomerization enthalpy for complexes that account for the bands at 2160 and 2124 cm(-1) of CO adsorbed on NaCl, estimated from the experiment, is 4.0 ± 0.2 kJ/mol. Quantum mechanical calculations by DFT methods applied to NaCl model clusters interacting with the CO molecule confirm the existence of two potential wells with adsorption and isomerization energies close to the experimentally measured values, and enable us to estimate the height of the potential barrier between the two adsorption states.
吸附在氯化钠和溴化钾薄膜上的一氧化碳的变温傅里叶变换红外光谱显示出键合异构现象，即与相同阳离子位点形成碳键和氧键吸附络合物。并非所有位点都能参与其中，只有位于微晶的扭结、边缘或台阶处的三配位或四配位阳离子才行。对于氯化钠，这些吸附络合物对应于2175和2160 cm⁻¹处的高频（HF）碳 - 氧伸缩带。在2115和2124 cm⁻¹处发现了氧键合一氧化碳的相应低频（LF）带。在溴化钾的光谱中，高频带分辨不清，只能清楚地看到一个低频带，在2124 cm⁻¹附近。根据实验估计，在氯化钠上吸附的一氧化碳的2160和2124 cm⁻¹处的带所对应的络合物的异构化焓值为4.0±0.2 kJ/mol。应用于与一氧化碳分子相互作用的氯化钠模型簇的密度泛函理论（DFT）方法的量子力学计算证实了存在两个势阱，其吸附和异构化能量接近实验测量值，并使我们能够估计两个吸附态之间的势垒高度。
