Dipartimento di Chimica IFM, Università di Torino and NIS, Nanostructured Interfaces and Surfaces Centre of Excellence, Via P. Giuria 7, I - 10125 Torino, Italy.
Chemistry. 2010 Jun 18;16(23):6776-85. doi: 10.1002/chem.201000546.
The formation of O(2) (-) radical anions by contact of O(2) molecules with a Na pre-covered MgO surface is studied by a combined EPR and quantum chemical approach. Na atoms deposited on polycrystalline MgO samples are brought into contact with O(2). The typical EPR signal of isolated Na atoms disappears when the reaction with O(2) takes place and new paramagnetic species are observed, which are attributed to different surface-stabilised O(2) (-) radicals. Hyperfine sublevel correlation (HYSCORE) spectroscopy allows the superhyperfine interaction tensor of O(2) (-)Na(+) species to be determined, demonstrating the direct coordination of the O(2) (-) adsorbate to surface Na(+) cations. DFT calculations enable the structural details of the formed species to be determined. Matrix-isolated alkali superoxides are used as a standard to enable comparison of the formed species, revealing important and unexpected contributions of the MgO matrix in determining the electronic structure of the surface-stabilised Na(+)-O(2) (-) complexes.
通过电子顺磁共振（EPR）和量子化学方法相结合的手段，研究了 O(2) 分子与预先覆盖有 Na 的 MgO 表面接触时 O(2) (-) 自由基阴离子的形成。将沉积在多晶 MgO 样品上的 Na 原子与 O(2) 接触。当与 O(2) 发生反应时，典型的孤立 Na 原子的 EPR 信号消失，观察到新的顺磁物种，这些物种归因于不同的表面稳定的 O(2) (-) 自由基。超精细亚层相关（HYSCORE）光谱允许确定 O(2) (-)Na(+) 物种的超精细相互作用张量，证明了 O(2) (-) 吸附物与表面 Na(+) 阳离子的直接配位。DFT 计算可以确定形成的物种的结构细节。将基质隔离的碱超氧化物用作标准，以比较形成的物种，揭示了 MgO 基质在确定表面稳定的 Na(+)-O(2) (-) 配合物的电子结构方面的重要和意外贡献。
