Weinstock Ira A
Department of Chemistry, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel.
Inorg Chem. 2008 Jan 21;47(2):404-6. doi: 10.1021/ic701885q. Epub 2007 Dec 20.
Efforts to use the Marcus model to describe oxidations of the superoxide radical anion (O(2-)) by transition-metal complexes have failed dramatically, with discrepancies between theory and experiment spanning 13 orders of magnitude. As a result, the prevailing view is that these reactions involve some complex interactions that are not yet understood. We now show that once the familiar form of the Marcus cross relation (MCR) is modified to allow for the relatively small size of O(2-), excellent agreement is obtained between theory and experiment. This simple finding dispels the decades of uncertainty surrounding these reactions and provides a reliable method for determining whether oxidations of (O2)- occur via inner- or outer-sphere pathways. More generally, the modified MCR is applicable to any homogeneous electron-transfer process characterized by significant differences in size between electron donors and acceptors.
试图用马库斯模型来描述过渡金属配合物对超氧阴离子自由基（O(2-)）的氧化反应遭遇了极大失败，理论与实验之间的差异跨越了13个数量级。因此，普遍的观点是这些反应涉及一些尚未被理解的复杂相互作用。我们现在表明，一旦对马库斯交叉关系（MCR）的常见形式进行修改，以考虑到O(2-)相对较小的尺寸，理论与实验之间就能获得极佳的一致性。这一简单发现消除了围绕这些反应数十年的不确定性，并提供了一种可靠的方法来确定(O2)-的氧化反应是通过内球还是外球途径发生。更普遍地说，修改后的MCR适用于任何以电子供体和受体之间尺寸存在显著差异为特征的均相电子转移过程。
