Redox-active scandium oxide cluster inside a fullerene cage: spectroscopic, voltammetric, electron spin resonance spectroelectrochemical, and extended density functional theory study of Sc4O2@C80 and its ion radicals.
Redox-active scandium oxide cluster inside a fullerene cage: spectroscopic, voltammetric, electron spin resonance spectroelectrochemical, and extended density functional theory study of Sc4O2@C80 and its ion radicals.
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DOI：
10.1021/ja306728p
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发表时间：
2012-09
影响因子：
15
通讯作者：
A. Popov;N. Chen;Julio R. Pinzón;S. Stevenson;L. Echegoyen;L. Dunsch
中科院分区：
文献类型：
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作者：
A. Popov;N. Chen;Julio R. Pinzón;S. Stevenson;L. Echegoyen;L. Dunsch
用电子自旋共振（ESR）光谱电化学方法研究了具有钪的混合氧化还原态的簇合物Sc（4）O（2）@C（80）的阳离子和阴离子自由基的自旋密度分布.该化合物具有两个可逆的还原和氧化步骤，具有相对较小的电化学间隙为1.10 V。离子自由基的ESR谱具有丰富的超精细结构所造成的两对等价的Sc原子。具有较大超精细耦合常数的Sc基超精细结构表明，Sc（4）O（2）@C（80）的氧化和还原均为cavea氧化还原过程，这是内配体电化学的研究对象。通过扩展密度泛函理论和分子动力学模拟，对Sc（4）O（2）团簇中两种Sc原子的α（45）Sc）值进行了归属.在中性Sc（4）O（2）@C（80）中采用二价态的Sc原子在阳离子自由基中表现出特别大的耦合常数150.4 G，这是Sc基内嵌金属富勒烯的最高a（（45）Sc）值。这种高值是由位于六原子Sc（4）O（2）簇上的最高占据分子轨道（HOMO）的性质解释的。该HOMO是Sc-Sc键合MO，因此具有来自Sc（II）的4s原子轨道的大贡献。我们认为ESR光谱电化学在研究内嵌金属富勒烯的金属-金属键合和内嵌电化学中是一个非常有价值的实验工具。
The clusterfullerene Sc(4)O(2)@C(80) with a mixed redox state of scandium was found to be an exciting molecule for endohedral electrochemistry as demonstrated by means of an in situ electron spin resonance (ESR) spectroelectrochemical study of the spin density distribution in its electrochemically generated cation and anion radicals. The compound exhibits two reversible reduction and oxidation steps with a relatively small electrochemical gap of 1.10 V. The ESR spectra of the ion radicals have a rich hyperfine structure caused by two pairs of equivalent Sc atoms. The Sc-based hyperfine structure with large hyperfine coupling constants shows that both oxidation and reduction of Sc(4)O(2)@C(80) are in cavea redox processes, which is the subject of endohedral electrochemistry. The assignment of the experimentally determined a((45)Sc) values to the two types of Sc atoms in the Sc(4)O(2) cluster was accomplished by extended density functional theory and molecular dynamics simulations. Sc atoms adopting a divalent state in the neutral Sc(4)O(2)@C(80) exhibited an especially large coupling constant of 150.4 G in the cation radical, which is the record high a((45)Sc) value for Sc-based endohedral metallofullerenes. Such a high value is explained by the nature of the highest occupied molecular orbital (HOMO) localized on the six-atom Sc(4)O(2) cluster. This HOMO is a Sc-Sc bonding MO and hence has large contributions from the 4s atomic orbitals of Sc(II). We claim that ESR spectroelectrochemistry is an invaluable experimental tool in the studies of metal-metal bonding in endohedral metallofullerenes and in endohedral electrochemistry.