title: General Scheme for Oxidative Quenching of a Copper Bis-Phenanthroline Photosensitizer for Light-Driven Hydrogen Production.
abstract: A new, general reaction scheme for photocatalytic hydrogen production is presented based on oxidative quenching of a homoleptic copper(I) bis-1,10-phenanthroline photosensitizer (PS) by 1-methyl-4-phenyl-pyridinium (MPP(+) ) as the electron relay and subsequent regeneration of the so formed copper(II) complex by a sacrificial electron donor. Electron transfer from the relay to various cobalt based water reduction catalysts and subsequent H2 production was shown to close the catalytic cycle. Transient absorption experiments unambiguously confirmed the proposed pathway, both the oxidative quenching and subsequent regeneration of oxidized PS. Photocatalytic test runs further confirmed the role of MPP(+) and up to 10 turnovers were achieved in the relay. The performance limiting factor of the system was shown to be the decomplexation of the copper PS. Quantum yields of the system were 0.03 for H2 production, but 0.6 for MPP(.) formation, clearly indicating that unproductive pathways still prevail.
authors.affiliation: Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8049, Zurich, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Windisch
authors.affiliation: Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8049, Zurich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Orazietti
authors.affiliation: Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8049, Zurich, Switzerland.
authors.forename: P
authors.initials: P
authors.lastname: Hamm
authors.affiliation: Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8049, Zurich, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Alberto
authors.affiliation: Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8049, Zurich, Switzerland. benjamin.probst@uzh.ch.
authors.forename: B
authors.identifier: 0000-0001-8850-9685
authors.initials: B
authors.lastname: Probst
mesh_terms: D015655:1-Methyl-4-phenylpyridinium / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D008027:Light; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010618:Phenanthrolines / Q000737:chemistry*; D055668:Photochemical Processes; D017319:Photosensitizing Agents / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D010618:Phenanthrolines; D017319:Photosensitizing Agents; D003300:Copper; D006859:Hydrogen; D015655:1-Methyl-4-phenylpyridinium; C025205:1,10-phenanthroline
keywords: copper; oxidative quenching; photocatalysis; reaction mechanisms; time-resolved spectroscopy