Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
Inorg Chem. 2011 Feb 21;50(4):1368-77. doi: 10.1021/ic101943h. Epub 2011 Jan 18.
Iron corroles modified with a xanthene scaffold are delivered from easily available starting materials in abbreviated reaction times. These new iron corroles have been spectroscopically examined with particular emphasis on defining the oxidation state of the metal center. Investigation of their electronic structure using (57)Fe Mössbauer spectroscopy in conjunction with density functional theory (DFT) calculations reveals the non-innocence of the corrole ligand. Although these iron corroles contain a formal Fe(IV) center, the deprotonated corrole macrocycle ligand is one electron oxidized. The electronic ground state of these complexes is best described as an intermediate spin S = 3/2 Fe(III) site strongly antiferromagnetically coupled to the S = 1/2 of the monoradical dianion corrole [Fe(III)Cl-corrole(+•)]. We show here that iron corroles as well as xanthene-modified and hangman xanthene iron corroles are redox active and catalyze the disproportionation of hydrogen peroxide via the catalase reaction, and that this activity scales with the oxidation potential. The meso position of corrole macrocycle is susceptible toward nucleophilic attack during catalase turnover. The reactivity of peroxide within the hangman cleft reported here adds to the emerging theme that corroles are good at catalyzing two-electron activation of the oxygen-oxygen bond in a variety of substrates.
铁叶啉经香豆素骨架修饰后，可由易得的起始原料，在较短的反应时间内得到。这些新型铁叶啉已通过光谱学进行了研究，特别强调了金属中心氧化态的定义。使用 (57)Fe Mössbauer 光谱学结合密度泛函理论（DFT）计算研究其电子结构，揭示了叶啉配体的非中性。尽管这些铁叶啉含有形式上的 Fe(IV)中心，但去质子化的叶啉大环配体被氧化了一个电子。这些配合物的电子基态最好描述为中间自旋 S = 3/2 Fe(III)位点与单自由基二阴离子叶啉 [Fe(III)Cl-corrole(+•)]的 S = 1/2 强烈反铁磁耦合。我们在这里表明，铁叶啉以及香豆素修饰和绞刑架香豆素铁叶啉都是氧化还原活性的，并通过过氧化氢酶反应催化过氧化氢的歧化，并且这种活性与氧化电位成正比。叶啉大环的中位置在过氧化氢酶循环过程中易受亲核攻击。这里报道的绞刑架裂缝内过氧化物的反应性增加了一个新兴主题，即叶啉擅长在各种底物中催化氧-氧键的两电子活化。
