Structural Evolution of the [(CO2)n(H2O)]-Cluster Anions: Quantifying the Effect of Hydration on the Excess Charge Accommodation Motif
Structural Evolution of the [(CO2)n(H2O)]-Cluster Anions: Quantifying the Effect of Hydration on the Excess Charge Accommodation Motif
复制标题
[(CO2)n(H2O)]-簇阴离子的结构演化：量化水合对过量电荷调节基序的影响
DOI：
10.1021/jp903578e
复制
发表时间：
2009
期刊：
影响因子：
2.9
通讯作者：
and T. Nagata
中科院分区：
文献类型：
--
作者：
A. Muraoka;Y. Inokuchi;N. Hammer;J.-W. Shin;M. A. Johnson;and T. Nagata
用红外光解离光谱研究了[(CO_2)n(H_2O)]−团簇阴离子在2800−-3800 cm-−-1范围内的光谱性质。观察到的IPD谱表明，在N=4时，振动带特征发生了剧烈的变化，表明单水团簇阴离子的结构演化发生了急剧的间断。然后=2和3光谱是由3600厘米−1附近的一系列尖锐的带组成，这是归属于以双离子氢键(DIHB)构型结合到C2O4−上的H2O的伸缩振动，如前所述(J.化学)。物理2005、122、094303)。在≥4谱中，在≈3 30 0 cm−1处还出现了一对强吸收带。通过从头计算，在−2/6-31+G*水平上，330 0 cm−1谱带被指定为H2O的弯曲泛音和氢键的OH振动，通过单O−H···O键与CO2CO2分子结合.因此，[(CO_2)n(H_2O)]−的结构随着团簇大小的变化而变化，在n=2和3的较小的团簇中，DIHB到C_2O_4的−是有利的，而在n为−=4的较大的团簇中，CO_2≥是通过形成单一的离子氢键构型而优先稳定的。
The [(CO2)n(H2O)]−cluster anions are studied using infrared photodissociation (IPD) spectroscopy in the 2800−3800 cm−1range. The observed IPD spectra display a drastic change in the vibrational band features atn= 4, indicating a sharp discontinuity in the structural evolution of the monohydrated cluster anions. Then= 2 and 3 spectra are composed of a series of sharp bands around 3600 cm−1, which are assignable to the stretching vibrations of H2O bound to C2O4−in a double ionic hydrogen-bonding (DIHB) configuration, as was previously discussed (J. Chem. Phys.2005,122, 094303). In then≥ 4 spectrum, a pair of intense bands additionally appears at ≈3300 cm−1. With the aid of ab initio calculations at the MP2/6-31+G* level, the 3300 cm−1bands are assigned to the bending overtone and the hydrogen-bonded OH vibration of H2O bound to CO2−via a single O−H···O linkage. Thus, the structures of [(CO2)n(H2O)]−evolve with cluster size such that DIHB to C2O4−is favored in the smaller clusters withn= 2 and 3 whereas CO2−is preferentially stabilized via the formation of a single ionic hydrogen-bonding (SIHB) configuration in the larger clusters withn≥ 4.