title: Model of the iron hydrogenase active site covalently linked to a ruthenium photosensitizer: synthesis and photophysical properties.
abstract: A model of the iron hydrogenase active site with the structure [(mu-ADT)Fe2(CO)6] (ADT = azadithiolate (S-CH2-NR-CH2-S), (2: R = 4-bromophenyl, 3: R = 4-iodophenyl)) has been assembled and covalently linked to a [Ru(terpy)2]2+ photosensitizer. This trinuclear complex 1 represents one synthetic step toward the realization of our concept of light-driven proton reduction. A rigid phenylacetylene tether has been incorporated as the linking unit in 1 in order to prolong the lifetime of the otherwise short-lived [Ru(terpy)2]2+ excited state. The success of this strategy is demonstrated by comparison of the photophysical properties of 1 and of two related ruthenium complexes bearing acetylenic terpyridine ligands, with those of [Ru(terpy)2]2+. IR and electrochemical studies reveal that the nitrogen heteroatom of the ADT bridge has a marked influence on the electronic properties of the [Fe2(CO)6] core. Using the Rehm-Weller equation, the driving force for an electron transfer from the photoexcited *[Ru(terpy)2]2+ to the diiron site in 1 was calculated to be uphill by 0.59 eV. During the construction of the trinuclear complex 1, n-propylamine has been identified as a decarbonylation agent on the [(mu-ADT)Fe2(CO)6] portion of the supermolecule. Following this procedure, the first azadithiolate-bridged dinuclear iron complex coordinated by a phosphine ligand [(mu-ADT)Fe2(CO)5PPh3] (4, R = 4-bromophenyl) was synthesized.
authors.affiliation: Departments of Organic Chemistry and Structural Chemistry, Arrhenius Laboratory, Stockholm University, S-10691 Stockholm, Sweden.
authors.forename: Sascha
authors.initials: S
authors.lastname: Ott
authors.forename: Magnus
authors.initials: M
authors.lastname: Borgström
authors.forename: Mikael
authors.initials: M
authors.lastname: Kritikos
authors.forename: Reiner
authors.initials: R
authors.lastname: Lomoth
authors.forename: Jonas
authors.initials: J
authors.lastname: Bergquist
authors.forename: Björn
authors.initials: B
authors.lastname: Akermark
authors.forename: Leif
authors.initials: L
authors.lastname: Hammarström
authors.forename: Licheng
authors.initials: L
authors.lastname: Sun
mesh_terms: D001665:Binding Sites; D004563:Electrochemistry; D006864:Hydrogenase / Q000737:chemistry* / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis*; D017319:Photosensitizing Agents / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D013329:Structure-Activity Relationship
chemical_list: D007506:Iron-Sulfur Proteins; D008024:Ligands; D009942:Organometallic Compounds; D017319:Photosensitizing Agents; D012428:Ruthenium; C118830:iron hydrogenase; D006864:Hydrogenase