title: Assembly, structure, and reactivity of Cu₄S and Cu₃S models for the nitrous oxide reductase active site, Cu(Z)*.
abstract: Bridging diphosphine ligands were used to facilitate the assembly of copper clusters with single sulfur atom bridges that model the structure of the Cu(Z)* active site of nitrous oxide reductase. Using bis(diphenylphosphino)amine (dppa), a [Cu(I)4(μ4-S)] cluster with N-H hydrogen bond donors in the secondary coordination sphere was assembled. Solvent and anion guests were found docking to the N-H sites in the solid state and in the solution phase, highlighting a kinetically viable pathway for substrate introduction to the inorganic core. Using bis(dicyclohexylphosphino)methane (dcpm), a [Cu(I)3(μ3-S)] cluster was assembled preferentially. Both complexes exhibited reversible oxidation events in their cyclic voltammograms, making them functionally relevant to the Cu(Z)* active site that is capable of catalyzing a multielectron redox transformation, unlike the previously known [Cu(I)4(μ4-S)] complex from Yam and co-workers supported by bis(diphenylphosphino)methane (dppm). The dppa-supported [Cu(I)4(μ4-S)] cluster reacted with N3(-), a linear triatomic substrate isoelectronic to N2O, in preference to NO2(-), a bent triatomic. This [Cu(I)4(μ4-S)] cluster also bound I(-), a known inhibitor of Cu(Z)*. Consistent with previous observations for nitrous oxide reductase, the tetracopper model complex bound the I(-) inhibitor much more strongly and rapidly than the substrate isoelectronic to N2O, producing unreactive μ3-iodide clusters including a [Cu3(μ3-S)(μ3-I)] complex related to the [Cu4(μ4-S)(μ2-I)] form of the inhibited enzyme.
authors.affiliation: Department of Chemistry, University of Illinois at Chicago , 845 West Taylor Street, Chicago, Illinois 60607, United States.
authors.forename: Brittany J
authors.initials: BJ
authors.lastname: Johnson
authors.forename: Sergey V
authors.initials: SV
authors.lastname: Lindeman
authors.forename: Neal P
authors.initials: NP
authors.lastname: Mankad
mesh_terms: D003300:Copper / Q000737:chemistry / Q000378:metabolism*; D018360:Crystallography, X-Ray; D055664:Electrochemical Techniques; D004789:Enzyme Activation; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry / Q000378:metabolism*; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D055668:Photochemical Processes; D013455:Sulfur / Q000737:chemistry / Q000378:metabolism*
chemical_list: D009942:Organometallic Compounds; D013455:Sulfur; D003300:Copper; D010088:Oxidoreductases; C022763:nitrous oxide reductase