RUI: Halide Oxidation by Peroxometal Complexes: Mechanism and Reactivity

Martha Reynolds博士，高露洁大学化学系，受到化学系无机、生物无机和有机金属化学项目的支持，研究卤化物离子被金属结合过氧化物氧化。本文将合成一系列新的钼（VI）、钒(V)和钨（VI）过氧配合物，这些配合物具有系统变化的给电子性质，并将分光光度法测定其对溴化物氧化的反应性。这些实验将验证一个假设，即螯合配体的电子结构以可预测的方式控制过氧键的强度，而过氧键的强度反过来又控制复合物作为氧化剂的反应性。将检查含有过氧化物和溴或氯直接与金属结合的配合物的反应性。这些物种代表了卤化物离子的过氧化物氧化过程中可能的中间体。由于过氧和金属-氧的振动频率对化学变化的敏感性，红外光谱将用于获得溴化物氧化机理的更详细信息，红外光谱电化学将用于比较过氧金属配合物的一电子和二电子氧化化学的分子细节。含过氧化物的金属配合物可作为多种有机化合物氧化或溴化的催化剂。这种催化剂的一个生物例子是钒溴过氧化物酶，一种在海藻中发现的酶，它能产生氧化溴，以保护海藻免受捕食者或微生物的侵害。该项目将增加对过氧化物金属复合物的了解，从而增加对钒卤素过氧化物酶的了解，并有望开发新的氧化和溴化催化剂，这些催化剂可能在抗癌、抗菌和胰岛素模拟药物的合成以及更广泛的氧化或溴化有机化合物中被证明是有用的。从事这项研究的学生将获得化学合成、光谱和电化学技术以及化学动力学方面的知识。

Dr. Martha Reynolds, Department of Chemistry, Colgate University, is supported by the Inorganic, Bioinorganic, and Organometallic Chemistry Program of the Chemistry Division for a study of the oxidation of halide ions by metal-bound peroxides. A series of new molybdenum(VI), vanadium(V), and tungsten(VI) peroxo complexes with ligands that vary systematically in their electron-donating properties will be synthesized and the reactivity toward bromide oxidation will be measured spectrophotometrically. These experiments will test the hypothesis that the electronic structure of a chelating ligand controls the strength of the peroxo bond in predictable ways, which in turn governs the reactivity of the complex as an oxidant. The reactivity of complexes that contain both peroxide and bromide or chloride directly bound to the metal will be examined. Such species represent possible intermediates in the peroxometal-mediated oxidation of halide ion. Because of the sensitivity of peroxo and metal-oxo vibrational frequencies to chemical changes, infrared spectroscopy will be used to obtain more detailed information on the mechanism of bromide oxidation and infrared-spectroelectrochemistry will be employed to compare the molecular details of the one- and two-electron oxidation chemistry of peroxometal complexes.Peroxide-containing metal complexes find application as catalysts for the oxidation or bromination of a variety of organic compounds. A biological example of such a catalyst is vanadium bromoperoxidase, an enzyme found in seaweed that produces oxidized bromine for the purpose of protecting the seaweed against predators or microorganisms. This project will provide an increased understanding of peroxometal complexes - and thereby of vanadium haloperoxidase enzymes - and holds promise for the development of new oxidation and bromination catalysts that may prove useful in the synthesis of anticancer, antimicrobial, and insulin-mimetic pharmaceuticals, and of oxidized or brominated organic compounds more generally. Students undertaking this research will gain facility in chemical synthesis, spectroscopic and electrochemical techniques, and chemical kinetics.