title: Perturbing the Copper(III)-Hydroxide Unit through Ligand Structural Variation.
abstract: Two new ligand sets, (pipMe)LH2 and (NO2)LH2 ((pipMe)L = N,N'-bis(2,6-diisopropylphenyl)-1-methylpiperidine-2,6-dicarboxamide, (NO2)L = N,N'-bis(2,6-diisopropyl-4-nitrophenyl)pyridine-2,6-dicarboxamide), are reported which are designed to perturb the overall electronics of the copper(III)-hydroxide core and the resulting effects on the thermodynamics and kinetics of its hydrogen-atom abstraction (HAT) reactions. Bond dissociation energies (BDEs) for the O-H bonds of the corresponding Cu(II)-OH2 complexes were measured that reveal that changes in the redox potential for the Cu(III)/Cu(II) couple are only partially offset by opposite changes in the pKa, leading to modest differences in BDE among the three compounds. The effects of these changes were further probed by evaluating the rates of HAT by the corresponding Cu(III)-hydroxide complexes from substrates with C-H bonds of variable strength. These studies revealed an overarching linear trend in the relationship between the log k (where k is the second-order rate constant) and the ΔH of reaction. Additional subtleties in measured rates arise, however, that are associated with variations in hydrogen-atom abstraction barrier heights and tunneling efficiencies over the temperature range from -80 to -20 °C, as inferred from measured kinetic isotope effects and corresponding electronic-structure-based transition-state theory calculations.
authors.affiliation: Department of Chemistry, Center for Metals in Biocatalysis, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota , 207 Pleasant Street Southeast, Minneapolis, Minnesota 55455, United States.
authors.forename: Debanjan
authors.initials: D
authors.lastname: Dhar
authors.affiliation: Department of Chemistry, Center for Metals in Biocatalysis, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota , 207 Pleasant Street Southeast, Minneapolis, Minnesota 55455, United States.
authors.forename: Gereon M
authors.initials: GM
authors.lastname: Yee
authors.affiliation: Department of Chemistry, Center for Metals in Biocatalysis, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota , 207 Pleasant Street Southeast, Minneapolis, Minnesota 55455, United States.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Spaeth
authors.affiliation: Department of Chemistry, Center for Metals in Biocatalysis, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota , 207 Pleasant Street Southeast, Minneapolis, Minnesota 55455, United States.
authors.forename: David W
authors.initials: DW
authors.lastname: Boyce
authors.affiliation: Department of Chemistry, Center for Metals in Biocatalysis, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota , 207 Pleasant Street Southeast, Minneapolis, Minnesota 55455, United States.
authors.forename: Hongtu
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Center for Metals in Biocatalysis, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota , 207 Pleasant Street Southeast, Minneapolis, Minnesota 55455, United States.
authors.forename: Büsra
authors.initials: B
authors.lastname: Dereli
authors.affiliation: Department of Chemistry, Center for Metals in Biocatalysis, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota , 207 Pleasant Street Southeast, Minneapolis, Minnesota 55455, United States.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Cramer
authors.affiliation: Department of Chemistry, Center for Metals in Biocatalysis, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota , 207 Pleasant Street Southeast, Minneapolis, Minnesota 55455, United States.
authors.forename: William B
authors.initials: WB
authors.lastname: Tolman
mesh_terms: D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D006878:Hydroxides / Q000737:chemistry*; D007700:Kinetics; D008024:Ligands
chemical_list: D006878:Hydroxides; D008024:Ligands; D003300:Copper