title: Excitation wavelength dependent O2 release from copper(II)-superoxide compounds: laser flash-photolysis experiments and theoretical studies.
abstract: Irradiation of the copper(II)-superoxide synthetic complexes [(TMG3tren)Cu(II)(O2)](+) (1) and [(PV-TMPA)Cu(II)(O2)](+) (2) with visible light resulted in direct photogeneration of O2 gas at low temperature (from -40 °C to -70 °C for 1 and from -125 to -135 °C for 2) in 2-methyltetrahydrofuran (MeTHF) solvent. The yield of O2 release was wavelength dependent: λexc = 436 nm, ϕ = 0.29 (for 1), ϕ = 0.11 (for 2), and λexc = 683 nm, ϕ = 0.035 (for 1), ϕ = 0.078 (for 2), which was followed by fast O2-recombination with [(TMG3tren)Cu(I)](+) (3) and [(PV-TMPA)Cu(I)](+) (4). Enthalpic barriers for O2 rebinding to the copper(I) center (∼10 kJ mol(-1)) and for O2 dissociation from the superoxide compound 1 (45 kJ mol(-1)) were determined. TD-DFT studies, carried out for 1, support the experimental results confirming the dissociative character of the excited states formed upon blue- or red-light laser excitation.
authors.affiliation: Department of Chemistry, The Johns Hopkins University , Baltimore, Maryland 21218, United States.
authors.forename: Claudio
authors.initials: C
authors.lastname: Saracini
authors.forename: Dimitrios G
authors.initials: DG
authors.lastname: Liakos
authors.forename: Jhon E
authors.initials: JE
authors.lastname: Zapata Rivera
authors.forename: Frank
authors.initials: F
authors.lastname: Neese
authors.forename: Gerald J
authors.initials: GJ
authors.lastname: Meyer
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Karlin
mesh_terms: D003300:Copper / Q000737:chemistry*; D007834:Lasers; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D010782:Photolysis; D011789:Quantum Theory; D013481:Superoxides / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D013481:Superoxides; D003300:Copper; D010100:Oxygen