title: 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.
abstract: 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 lambda max approximately 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.
authors.affiliation: Institut des Sciences Moléculaires de Marseille, ISM /BiosCiences UMR-CNRS 6263, Aix-Marseille Université, Centre Scientifique de Saint-Jérôme, Service 342, 13397 Marseille cedex 20, France.
authors.forename: Wadih
authors.initials: W
authors.lastname: Ghattas
authors.forename: Michel
authors.initials: M
authors.lastname: Giorgi
authors.forename: Yasmina
authors.initials: Y
authors.lastname: Mekmouche
authors.forename: Tsunehiro
authors.initials: T
authors.lastname: Tanaka
authors.forename: Antal
authors.initials: A
authors.lastname: Rockenbauer
authors.forename: Marius
authors.initials: M
authors.lastname: Réglier
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Hitomi
authors.forename: A Jalila
authors.initials: AJ
authors.lastname: Simaan
mesh_terms: D000388:Air; D000598:Amino Acids, Cyclic / Q000737:chemistry*; D000621:Aminoisobutyric Acids / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D005030:Ethylenes / Q000138:chemical synthesis* / Q000737:chemistry; D016166:Free Radical Scavengers / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry; D010084:Oxidation-Reduction; D010618:Phenanthrolines / Q000737:chemistry; D010880:Piperidines / Q000737:chemistry; D011789:Quantum Theory; D017382:Reactive Oxygen Species / Q000737:chemistry
chemical_list: D000598:Amino Acids, Cyclic; D000621:Aminoisobutyric Acids; D005030:Ethylenes; D016166:Free Radical Scavengers; D010618:Phenanthrolines; D010880:Piperidines; D017382:Reactive Oxygen Species; C009926:picoperidamine; C023863:1-aminocyclopropane-1-carboxylic acid; D003300:Copper; C036216:ethylene; D006861:Hydrogen Peroxide; D009584:Nitrogen