title: [Me4N](Ni(II)(BEAAM)): a synthetic model for nickel superoxide dismutase that contains Ni in a mixed amine/amide coordination environment.
abstract: Nickel superoxide dismutase (NiSOD) is a metalloenzyme that converts O2*- into H2O2 and O2 by cycling between Ni(II) and Ni(III) oxidation states. Reduced NiSOD contains Ni(II) in a square-planar N2S2 coordination environment formed by two cysteinate S atoms, an amide N, and an amine N to Ni(II). [Me4N](Ni(II)(BEAAM)) represents the first NiN2S2 complex containing Ni in a mixed amine/amide environment. [Me4](Ni(II)(BEAAM)) contains Ni-S bonds at 2.177(2) and 2.137(2) A and Ni-N bonds at 1.989(7) and 1.858(6) A, which compare well with the metalloenzyme. Orange solutions of [Me(4)N](Ni(II)(BEAAM)) in MeCN are diamagnetic and stable toward O2 for weeks. A quasireversible Ni(II/III) redox couple is observed for [Ni(II)(BEAAM)](NMe4) at 0.12(1) V vs Ag/AgCl. These data suggest that NiSOD utilizes the mixed amine/amide ligands to modulate the Ni(II/III) redox couple to best match the O2*- reduction/oxidation couples while maintaining O2 stability.
authors.affiliation: Department of Chemistry/216, University of Nevada, Reno, Reno, Nevada 89557, USA. shearer@chem.unr.edu
authors.forename: Jason
authors.initials: J
authors.lastname: Shearer
authors.forename: Ningfeng
authors.initials: N
authors.lastname: Zhao
mesh_terms: D000577:Amides / Q000737:chemistry; D000588:Amines / Q000737:chemistry; D008024:Ligands; D008956:Models, Chemical; D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D013455:Sulfur / Q000737:chemistry; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000378:metabolism
chemical_list: D000577:Amides; D000588:Amines; D008024:Ligands; D013455:Sulfur; D009532:Nickel; D013482:Superoxide Dismutase