Warren Jeffrey J, Mayer James M
University of Washington, Department of Chemistry, Box 351700, Seattle, Washington 98195, USA.
J Am Chem Soc. 2008 Mar 5;130(9):2774-6. doi: 10.1021/ja711057t. Epub 2008 Feb 8.
Hydrogen atom transfer (HAT) reactions of the bis(histidine) cytochrome active site models (TPP)FeII(ImH)2 (FeIIImH) and (TPP)Fe(Im)(ImH) (FeIIIIm) have been examined in acetonitrile solvent (TPP = tetraphenylporphyrin, ImH = 4-methylimidazole). The ascorbate derivative 5,6-isopropylidine ascorbate, hydroquinone, and the hydroxylamine TEMPOH all rapidly add H* to FeIIIIm to give FeIIImH. Similarly, the phenoxyl radical 2,4,6-tBu3C6H2O* and excess TEMPO* each oxidize FeIIImH to give FeIIIIm. On the basis of redox potential, pKa, and equilibrium measurements, the N-H bond in FeIIImH was found to have a bond dissociation free energy (BDFE) of 70 +/- 2 kcal mol(-1). A hydrogen atom transfer mechanism (concerted transfer of e- and H+) is indicated based on data for the ascorbate and TEMPO* reactions.
已在乙腈溶剂（TPP = 四苯基卟啉，ImH = 4 - 甲基咪唑）中研究了双（组氨酸）细胞色素活性位点模型（TPP）FeII（ImH）2（FeIIImH）和（TPP）Fe（Im）（ImH）（FeIIIIm）的氢原子转移（HAT）反应。抗坏血酸衍生物5,6 - 异亚丙基抗坏血酸、对苯二酚和羟胺TEMPOH都能迅速将H加到FeIIIIm上生成FeIIImH。同样，苯氧基自由基2,4,6 - tBu3C6H2O和过量的TEMPO各自将FeIIImH氧化生成FeIIIIm。基于氧化还原电位、pKa和平衡测量，发现FeIIImH中的N - H键的键解离自由能（BDFE）为70±2 kcal mol(-1)。基于抗坏血酸和TEMPO反应的数据表明存在氢原子转移机制（电子和H+的协同转移）。
