title: Visible light-driven hydrogen evolution from water catalyzed by a molecular cobalt complex.
abstract: An approximately planar tetradentate polypyridine ligand, 8-(1″,10″-phenanthrol-2″-yl)-2-(pyrid-2'-yl)quinoline (ppq), has been prepared by two sequential Friedländer condensations. The ligand readily accommodates Co(II) bearing two axial chlorides, and the resulting complex is reasonably soluble in water. In DMF the complex shows three well-behaved redox waves in the window of 0 to -1.4 V (vs SHE). However in pH 7 buffer the third wave is obscured by a catalytic current at -0.95 V, indicating hydrogen production that appears to involve a proton-coupled electron-transfer event. The complex [Co(ppq)Cl2] (6) in pH 4 aqueous solution, together with [Ru(bpy)3]Cl2 and ascorbic acid as a sacrificial electron donor, in the presence of blue light (λmax = 469 nm) produces hydrogen with an initial TOF = 586 h(-1).
authors.affiliation: Department of Chemistry, 112 Fleming Building, University of Houston , Houston, Texas 77204-5003, United States.
authors.forename: Lianpeng
authors.initials: L
authors.lastname: Tong
authors.forename: Ruifa
authors.initials: R
authors.lastname: Zong
authors.forename: Randolph P
authors.initials: RP
authors.lastname: Thummel