Second Sphere Control of Redox Catalysis: Selective Reduction of O2 to O2鈥?/sup> or H2O by an Iron Porphyrin Catalyst

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• 作者：Subhra Samanta ; Kaustuv Mittra ; Kushal Sengupta ; Sudipta Chatterjee ; Abhishek Dey
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：February 4, 2013
• 年：2013
• 卷：52
• 期：3
• 页码：1443-1453
• 全文大小：783K
• 年卷期：v.52,no.3(February 4, 2013)
• ISSN：1520-510X

文摘

鈥淐lick鈥?reaction has been utilized to synthesize porphyrin ligands possessing distal superstructures functionalized with ferrocenes, carboxylic acid esters, and phenols. Both structural and spectroscopic evidence indicate that hydrogen bonding interaction between the triazole residues resulting from the 鈥渃lick鈥?reaction promotes axial ligand binding into the sterically demanding distal pocket in preference to the open proximal side. An iron porphyrin complex with four ferrocene groups is found to bind O₂ and quantitatively reduce it by one electron to O₂^{鈥?/sup> in apolar organic solvents. However the same complex electro-catalytically reduces O₂ by four electrons to H₂O in aqueous medium under fast, moderate, and slow electron fluxes. This selectivity for O₂ reduction is governed by the reduction potential of the electron transfer site (i.e., ferrocene) which in turn is governed by the solvent. This catalyst mimics control of catalysis of an enzyme active site by a second sphere electron transfer residue which is often encountered in naturally occurring metallo-enzymes.}