ROLE OF THE DOUBLE-LAYER CATION ON THE POTENTIAL-DEPENDENT STRETCHING FREQUENCIES AND BINDING GEOMETRIES OF CARBON-MONOXIDE AT PLATINUM NONAQUEOUS INTERFACES
ROLE OF THE DOUBLE-LAYER CATION ON THE POTENTIAL-DEPENDENT STRETCHING FREQUENCIES AND BINDING GEOMETRIES OF CARBON-MONOXIDE AT PLATINUM NONAQUEOUS INTERFACES
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DOI：
10.1021/la00041a034
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发表时间：
1992-05-01
期刊：
影响因子：
3.9
通讯作者：
WEAVER, MJ
中科院分区：
文献类型：
--
作者：
ROTH, JD;WEAVER, MJ
在乙腈、甲醇、四氢呋喃（THF）和二氯甲烷中考察了双层阳离子对多晶铂表面饱和CO吸附层的电极电位依赖红外光谱性质的影响。选择这些溶剂是为了产生一系列介电和溶剂化环境。两类电解质进行了检查，涉及四烷基铵和碱金属阳离子。对于含有前电解质的每种溶剂，在整个可接近的电位范围内（从约100伏到约100伏）观察到几乎排他的末端CO配位。-2.5至1 V（相对于二茂铁-二茂铁），如通过在约2.5 V处的单个电位依赖性C-O伸缩带所证明的。2040-2090 cm-1。的nu（CO）的频率-电位斜率显着依赖于四烷基铵阳离子的大小。这种依赖性是近似一致的一个简单的双层模型的期望具有线性电位下降整个内层，与外部亥姆霍兹平面的位置由CO吸附层厚度加上非溶剂化阳离子半径确定。在碱金属（Li+，Na+，K+）电解质中的红外光谱产生了类似的末端nu（CO）特征，然而，该特征在相对负的电位下完全被位于ca. 1730-1800 cm-1。这种效应归因于由部分去溶剂化的碱金属阳离子和CO吸附层之间的刘易斯酸碱相互作用驱动的从末端到多重CO配位几何形状的电位诱导转换。类比指出，与阳离子诱导的多核羰基配合物的配位位移。
The influences of the double-layer cation upon the electrode potential-dependent infrared spectral properties of saturated CO adlayers on polycrystalline platinum have been examined in acetonitrile, methanol, tetrahydrofuran (THF), and dichloromethane. These solvents were chosen so to yield a range of dielectric and solvating environments. Two classes of electrolytes were examined, involving tetraalkyl-ammonium and alkali-metal cations. For each solvent containing the former electrolytes, near-exclusive terminal CO coordination was observed throughout the accessible potential range (from ca. -2.5 to 1 V vs ferrocenium-ferrocene), as evidenced by a single potential-dependent C-O stretching band at ca. 2040-2090 cm-1. The nu(CO) frequency-potential slopes depend significantly on the size of the tetraalkyl-ammonium cation. This dependence is approximately consistent with the expectations of a simple double-layer model featuring a linear potential drop throughout the inner layer, with the position of the outer Helmholtz plane being determined by the CO adlayer thickness plus the unsolvated cation radius. The infrared spectra in alkali-metal (Li+, Na+, K+) electrolytes yielded a similar terminal nu(CO) feature, which is, however, replaced entirely at relatively negative potentials by a band at ca. 1730-1800 cm-1. This effect is ascribed to a potential-induced conversion from terminal to multifold CO coordination geometries, driven by Lewis acid-base interactions between the partly desolvated alkali cations and the CO adlayer. Analogies are noted with cation-induced coordination shifts in polynuclear carbonyl complexes.