title: Incorporating peptides in the outer-coordination sphere of bioinspired electrocatalysts for hydrogen production.
abstract: Four new cyclic 1,5-diaza-3,7-diphosphacyclooctane ligands have been prepared and used to synthesize [Ni(P(Ph)(2)N(R)(2))(2)](2+) complexes in which R is a mono- or dipeptide. These complexes represent a first step in the development of an outer-coordination sphere for this class of complexes that can mimic the outer-coordination sphere of the active sites of hydrogenase enzymes. Importantly, these complexes retain the electrocatalytic activity of the parent [Ni(P(Ph)(2)N(Ph)(2))(2)](2+) complex in an acetonitrile solution with turnover frequencies for hydrogen production ranging from 14 to 25 s(-1) in the presence of p-cyanoanilinium trifluoromethanesulfonate and from 135 to 1000 s(-1) in the presence of protonated dimethylformamide, with moderately low overpotentials, ∼0.3 V. The addition of small amounts of water results in rate increases of 2-7 times. Unlike the parent complex, these complexes demonstrate dynamic structural transformations in solution. These results establish a building block from which larger peptide scaffolding can be added to allow the [Ni(P(R)(2)N(R')(2))(2)](2+) molecular catalytic core to begin to mimic the multifunctional outer-coordination sphere of enzymes.
authors: Chemical and Materials Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, USA.
authors: Avijita
authors: A
authors: Jain
authors: Sheri
authors: S
authors: Lense
authors: John C
authors: JC
authors: Linehan
authors: Simone
authors: S
authors: Raugei
authors: Herman
authors: H
authors: Cho
authors: Daniel L
authors: DL
authors: DuBois
authors: Wendy J
authors: WJ
authors: Shaw
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D040761:Biomimetic Materials / Q000138:chemical synthesis / Q000737:chemistry*; D002384:Catalysis; D004151:Dipeptides / Q000737:chemistry; D004563:Electrochemistry; D006859:Hydrogen / Q000737:chemistry*; D006864:Hydrogenase / Q000737:chemistry / Q000378:metabolism; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D009584:Nitrogen / Q000737:chemistry; D010455:Peptides / Q000737:chemistry*; D013057:Spectrum Analysis; D014867:Water / Q000737:chemistry
chemical_list: D000596:Amino Acids; D004151:Dipeptides; D008024:Ligands; D010455:Peptides; D014867:Water; D006859:Hydrogen; D006864:Hydrogenase; D009584:Nitrogen