title: Influence of Copper Oxidation State on the Bonding and Electronic Structure of Cobalt-Copper Complexes.
abstract: Heterobimetallic complexes that pair cobalt and copper were synthesized and characterized by a suite of physical methods, including X-ray diffraction, X-ray anomalous scattering, cyclic voltammetry, magnetometry, electronic absorption spectroscopy, electron paramagnetic resonance, and quantum chemical methods. Both Cu(II) and Cu(I) reagents were independently added to a Co(II) metalloligand to provide (py3tren)CoCuCl (1-Cl) and (py3tren)CoCu(CH3CN) (2-CH3CN), respectively, where py3tren is the triply deprotonated form of N,N,N-tris(2-(2-pyridylamino)ethyl)amine. Complex 2-CH3CN can lose the acetonitrile ligand to generate a coordination polymer consistent with the formula "(py3tren)CoCu" (2). One-electron chemical oxidation of 2-CH3CN with AgOTf generated (py3tren)CoCuOTf (1-OTf). The Cu(II)/Cu(I) redox couple for 1-OTf and 2-CH3CN is reversible at -0.56 and -0.33 V vs Fc(+)/Fc, respectively. The copper oxidation state impacts the electronic structure of the heterobimetallic core, as well as the nature of the Co-Cu interaction. Quantum chemical calculations showed modest electron delocalization in the (CoCu)(+4) state via a Co-Cu σ bond that is weakened by partial population of the Co-Cu σ antibonding orbital. By contrast, no covalent Co-Cu bonding is predicted for the (CoCu)(+3) analogue, and the d-electrons are fully localized at individual metals.
authors.affiliation: Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.
authors.forename: Reed J
authors.initials: RJ
authors.lastname: Eisenhart
authors.affiliation: Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.|Supercomputing Institute and Chemical Theory Center, University of Minnesota , Minneapolis, Minnesota 55455, United States.
authors.forename: Rebecca K
authors.initials: RK
authors.lastname: Carlson
authors.affiliation: Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Clouston
authors.affiliation: Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.
authors.forename: Victor G
authors.initials: VG
authors.lastname: Young
authors.affiliation: ChemMatCARS, University of Chicago , Argonne, Illinois 60439, United States.
authors.forename: Yu-Sheng
authors.initials: YS
authors.lastname: Chen
authors.affiliation: Max Planck Institut für Chemische Energiekonversion , Stiftstraβe 34-36, 45470 Mülheim an der Ruhr, Germany.
authors.forename: Eckhard
authors.initials: E
authors.lastname: Bill
authors.affiliation: Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.|Supercomputing Institute and Chemical Theory Center, University of Minnesota , Minneapolis, Minnesota 55455, United States.
authors.forename: Laura
authors.initials: L
authors.lastname: Gagliardi
authors.affiliation: Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.
authors.forename: Connie C
authors.initials: CC
authors.lastname: Lu