Identification of a Copper(I) Intermediate in the Conversion of 1-Aminocyclopropane Carboxylic Acid (ACC) into Ethylene by Cu(II)−ACC Complexes and Hydrogen Peroxide

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• 作者：Wadih Ghattas ; Michel Giorgi ; Yasmina Mekmouche ; Tsunehiro Tanaka ; Antal Rockenbauer ; Marius Ré ; glier ; Yutaka Hitomi ; A. Jalila Simaan
• 刊名：Inorganic Chemistry
• 出版年：2008
• 出版时间：June 2, 2008
• 年：2008
• 卷：47
• 期：11
• 页码：4627 - 4638
• 全文大小：810K
• 年卷期：v.47,no.11(June 2, 2008)
• ISSN：1520-510X

文摘

Several Cu(II) complexes with ACC (= 1-aminocyclopropane carboxylic acid) or AIB (= aminoisobutyric acid) were prepared using 2,2′-bipyridine, 1,10-phenanthroline, and 2-picolylamine ligands: [Cu(2,2′-bipyridine)(ACC)(H₂O)](ClO₄) (1a), [Cu(1,10-phenanthroline)(ACC)](ClO₄) (2a), [Cu(2-picolylamine)(ACC)](ClO₄) (3a), and [Cu(2,2′-bipyridine)(AIB)(H₂O)](ClO₄) (1b). All of the complexes were characterized by X-ray diffraction analysis. The Cu(II)−ACC complexes are able to convert the bound ACC moiety into ethylene in the presence of hydrogen peroxide, in an “ACC-oxidase-like” activity. A few equivalents of base are necessary to deprotonate H₂O₂ for optimum activity. The presence of dioxygen lowers the yield of ACC conversion into ethylene by the copper(II) complexes. During the course of the reaction of Cu(II)−ACC complexes with H₂O₂, brown species (EPR silent and λ_max ≈ 435 nm) were detected and characterized as being the Cu(I)−ACC complexes that are obtained upon reduction of the corresponding Cu(II) complexes by the deprotonated form of hydrogen peroxide. The geometry of the Cu(I) species was optimized by DFT calculations that reveal a change from square-planar to tetrahedral geometry upon reduction of the copper ion, in accordance with the observed nonreversibility of the redox process. In situ prepared Cu(I)−ACC complexes were also reacted with hydrogen peroxide, and a high level of ethylene formation was obtained. We propose Cu(I)−OOH as a possible active species for the conversion of ACC into ethylene, the structure of which was examined by DFT calculation.