Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, United States.
Department of Chemistry, University of California, Irvine, Irvine, California 92697, United States.
Inorg Chem. 2021 Mar 1;60(5):2905-2913. doi: 10.1021/acs.inorgchem.0c02742. Epub 2021 Feb 5.
A lignin-derived ligand, bis(2-hydroxy-3-methoxy-5-propylbenzyl)glycine (DHEG), was synthesized from 2-methoxy-4-propylphenol (dihydroeugenol (DHE)) and the amino acid glycine. Two mononuclear iron and manganese complexes of DHEG were prepared, characterized, and employed for the oxidation of chlorite to chlorine dioxide in aqueous solution. Peroxyacetic acid (PAA) was used as a "green" oxidant in the redox reactions to initiate the formation of high-valent Fe and Mn (IV)-OH intermediates. EPR studies verified the formation of a high-valent Mn species. Both Fe and Mn complexes catalyzed chlorite oxidation with bimolecular rate constants of 32 and 144 M s, respectively, at pH 4.0 and 25 °C. The Mn complex was found to be more efficient for chlorite oxidation with a turnover frequency of 17 h and remained active during subsequent additions of PAA. The rate of ClO decomposition with PAA/Mn-DHEG was first order in PAA and increased significantly as pH increased. A mechanism that accounts for all observations is presented.
一种木质素衍生的配体，双（2-羟基-3-甲氧基-5-丙基苄基）甘氨酸（DHEG），由 2-甲氧基-4-丙基苯酚（二氢丁香酚（DHE））和氨基酸甘氨酸合成。合成了两种单核铁和锰配合物 DHEG，并对其进行了表征，用于在水溶液中将亚氯酸盐氧化为二氧化氯。过氧乙酸（PAA）在氧化还原反应中用作“绿色”氧化剂，以引发高价 Fe 和 Mn（IV）-OH 中间体的形成。EPR 研究证实了高价 Mn 物种的形成。在 pH 4.0 和 25°C 下，Fe 和 Mn 配合物分别以双分子速率常数 32 和 144 M s 催化亚氯酸盐氧化。发现 Mn 配合物对亚氯酸盐氧化更有效，转化率为 17 h，并且在随后添加 PAA 时仍保持活性。PAA/Mn-DHEG 中 ClO 的分解速率与 PAA 呈一级关系，并随着 pH 的增加而显著增加。提出了一种可以解释所有观察结果的机制。
