A selective heterogeneous catalyst with the superoxide anion O₂^•− stable at room temperature, generated by treating Ti(OR)₄ (R = iPr, nBu) with H₂O₂, was previously reported and used for the oxidation of organic compounds. It was proposed that exceptional stability of the O₂^•− is resulted from its stabilization near Ti⁺⁴ cation on the TiO₂ surface with the participation of water molecules and/or OH groups. In this article, we performed high-resolution pulsed EPR study on the O₂^•− in this catalyst with the aim to obtain quantitative information about its interactions with the surrounding molecules. Our data has shown that the O₂^•− is involved in weak hyperfine interactions with protons in the nearest environment, which do not exceed a value of 2 MHz. It corresponds to an O_s…H distance of ≥ 3 Å that excludes the formation of hydrogen bonds. The analysis of possible structures of O₂^•− adsorption on TiO₂ surface taking into account our results and lack of radical mobility at room temperature previously observed in EPR spectra led us to suggest that the O₂^•− is stabilized in the form of superoxo bridge coordinated with two titanium atoms.

具有超氧阴离子 O ₂ ^•-在室温下稳定的选择性多相催化剂，通过 用 H ₂ O ₂处理 Ti(OR) ₄ ( R = iPr, nBu) 生成，先前已报道并用于有机化合物的氧化。有人提出，O ₂ ^{•- 的}特殊稳定性是由于其在TiO ₂表面上的Ti ⁺⁴阳离子附近的稳定性以及水分子和/或OH 基团的参与而产生的。在本文中，我们对 O ₂ ^•−进行了高分辨率脉冲 EPR 研究在这种催化剂中，目的是获得有关其与周围分子相互作用的定量信息。我们的数据表明，O ₂ ^•−与最近环境中的质子进行微弱的超精细相互作用，不超过 2 MHz 的值。它对应于≥ 3 Å的 O _s …H 距离，排除了氢键的形成。考虑到我们的结果和之前在 EPR 光谱中观察到的室温下自由基迁移率的缺乏，对 TiO ₂表面上O ₂ ^•−吸附的可能结构的分析使我们认为 O ₂ ^•−以超氧的形式稳定下来桥与两个钛原子配位。