Sahoo Limashree, Panwar Payal, Sastri Chivukula V, de Visser Sam P
Department of Chemistry, Indian Institute of Technology Guwahati, Assam 781039, India.
The Manchester Institute of Biotechnology and Department of Chemical Engineering, The University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
ACS Org Inorg Au. 2024 Sep 20;4(6):673-680. doi: 10.1021/acsorginorgau.4c00045. eCollection 2024 Dec 4.
The first-coordination sphere of catalysts is known to play a crucial role in reaction mechanisms, but details of how equatorial ligands influence the reactivity remain unknown. Heteroatom ligated to the equatorial position of iron centers in nonheme iron metalloenzymes modulates structure and reactivity. To investigate the impact of equatorial heteroatom substitution on chlorite oxidation, we synthesized and characterized three novel mononuclear nonheme iron(II) complexes with a pentadentate bispidine scaffold. These complexes feature systematic substitutions at the equatorial position in the bispidine ligand framework where the pyridine group is replaced with NMe, SMe, and OMe groups. The three iron(II)-bispidine complexes were subjected to studies in chlorite oxidation reactions as a model pathway for oxygen atom transfer. Chlorine oxyanions, which have the halide in an oxidation state ranging from +1 to +7, have numerous applications but can contaminate water bodies, and this demands urgent environmental remediation. Chlorite, a common precursor to chlorine dioxide, is of particular interest due to the superior antimicrobial activity of chlorine dioxide. Moreover, its generation leads to fewer harmful byproducts in water treatment. Here, we demonstrate that these complexes can produce chlorine dioxide from chlorite in acetate buffer at room temperature and pH 5.0, oxidizing chlorite through the in situ formation of high-valent iron(IV)-oxo intermediates. This study establishes how subtle changes in the coordination sphere around iron can influence the reactivity.
众所周知，催化剂的第一配位层在反应机理中起着关键作用，但关于赤道配体如何影响反应活性的细节仍不清楚。连接在非血红素铁金属酶中铁中心赤道位置的杂原子会调节结构和反应活性。为了研究赤道杂原子取代对亚氯酸盐氧化的影响，我们合成并表征了三种具有五齿联吡啶支架的新型单核非血红素铁（II）配合物。这些配合物在联吡啶配体框架的赤道位置有系统的取代，其中吡啶基团被NMe、SMe和OMe基团取代。对这三种铁（II）-联吡啶配合物进行了亚氯酸盐氧化反应的研究，作为氧原子转移的模型途径。氧化态从+1到+7的含卤氯酸根有许多应用，但会污染水体，这需要紧急的环境修复。亚氯酸盐是二氧化氯的常见前体，由于二氧化氯具有优异的抗菌活性而特别受关注。此外，在水处理中其生成的有害副产物较少。在这里，我们证明这些配合物在室温及pH 5.0的醋酸盐缓冲液中能从亚氯酸盐产生二氧化氯，通过原位形成高价铁（IV）-氧中间体氧化亚氯酸盐。这项研究确定了铁周围配位层的细微变化如何影响反应活性。
