title: Sulfonated diiron complexes as water-soluble models of the [Fe-Fe]-hydrogenase enzyme active site.
abstract: A series of diiron complexes developed as fundamental models of the two-iron subsite in the [FeFe]-hydrogenase enzyme active site show water-solubility by virtue of a sulfonate group incorporated into the -SCH(2)NRCH(2)S- dithiolate unit that bridges two Fe(I)(CO)(2)L moieties. The sulfanilic acid group imparts even greater water solubility in the presence of β-cyclodextrin, β-CyD, for which NMR studies suggest aryl-sulfonate inclusion into the cyclodextrin cavity as earlier demonstrated in the X-ray crystal structure of 1Na·2 β-CyD clathrate, where 1Na = Na(+)(μ-SCH(2)N(C(6)H(4)SO(3)(-))CH(2)S-)[Fe(CO)(3)](2), (Singleton et al., J. Am. Chem. Soc.2010, 132, 8870). Electrochemical analysis of the complexes for potential as electrocatalysts for proton reduction to H(2) finds the presence of β-CyD to diminish response, possibly reflecting inhibition of structural rearrangements required of the diiron unit for a facile catalytic cycle. Advantages of the aryl sulfonate approach include entry into a variety of water-soluble derivatives from the well-known (μ-SRS)[Fe(CO)(3)](2) parent biomimetic, that are stable in O(2)-free aqueous solutions.
authors.affiliation: Department of Chemistry, Texas A&M University, College Station, Texas 77843, USA.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Singleton
authors.forename: Danielle J
authors.initials: DJ
authors.lastname: Crouthers
authors.forename: Robert P
authors.initials: RP
authors.lastname: Duttweiler
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Reibenspies
authors.forename: Marcetta Y
authors.initials: MY
authors.lastname: Darensbourg
mesh_terms: D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D005290:Ferric Compounds / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D006864:Hydrogenase / Q000737:chemistry* / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D012995:Solubility; D013237:Stereoisomerism; D013425:Sulfanilic Acids / Q000737:chemistry* / Q000378:metabolism; D014867:Water / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; D007506:Iron-Sulfur Proteins; D013425:Sulfanilic Acids; D014867:Water; C118830:iron hydrogenase; D006864:Hydrogenase