A Monomeric Side-On Superoxocopper(II) Complex: Cu(O2)(HB(3-tBu-5-iPrpz)3)

Fujisawa, Kiyoshi; Tanaka, Masako; Moro‐oka, Yoshihiko; Kitajima, Nobumasa

doi:10.1021/ja00105a069

Cited by 274 publications

(251 citation statements)

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“…For example, a m( 16 O- 16 O) frequency of 1,122 cm À1 was used to identify a 1:1 Cu-O 2 species supported by a tris(2-dimethylaminoethyl)amine ligand as a superoxo complex (1, Structure 1) [17]. A different Cu-O 2 complex 2 with the tridentate ligand HB(3-t-Bu-5-iPrpz) 3 had a RR peak at 1,112 cm À1 for the 16 O- 16 O vibration, supporting its assignment as a superoxo species as well [18,19].…”

Section: Introductionmentioning

confidence: 74%

How useful are vibrational frequencies of isotopomeric O2 fragments for assessing local symmetry? Some simple systems and the vexing case of a galactose oxidase model

et al. 2005

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Section: Introductionmentioning

confidence: 74%

How useful are vibrational frequencies of isotopomeric O2 fragments for assessing local symmetry? Some simple systems and the vexing case of a galactose oxidase model

et al. 2005

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“…From a redox perspective, the coordination of molecular oxygen to a supported LCu(I) species (where we use L generically to represent a single ligand or multiple ligands) may be considered formally to proceed either without a change of the copper oxidation state or with one or two electrons transferred from the metal resulting in formal LCu(II)O 2 (-) and LCu(III)O 2 (2-) products, respectively. As molecular oxygen itself has a triplet electronic ground state, one might expect relatively weakly coupled LCu(I)O 2 species also to have triplet ground states, and the singlet and triplet states might be expected to have similar energies for the biradical-like LCu(II)O 2 (-) species, depending on the nature of the coupling between the open-shell d 9 Cu(II) ion and the superoxide radical anion. The LCu(III)O 2 (2-) species, on the other hand, would be expected to have singlet ground states given the closed-shell character of typical d 8 copper complexes and the peroxide dianion.…”

Section: Introductionmentioning

confidence: 99%

Stereoelectronic Effects on Molecular Geometries and State-Energy Splittings of Ligated Monocopper Dioxygen Complexes

et al. 2008

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The relative energies of side-on versus end-on binding of molecular oxygen to a supported Cu(I) species, and the singlet versus triplet nature of the ground electronic state, are sensitive to the nature of the supporting ligands and, in particular, depend upon their geometric arrangement relative to the O 2 binding site. Highly correlated ab initio and density functional theory electronic structure calculations demonstrate that optimal overlap (and oxidative charge transfer) occurs for the side-on geometry, and this is promoted by ligands that raise the energy, thereby enhancing resonance, of the filled Cu d xz orbital that hybridizes with the in-plane π* orbital of O 2 . Conversely, ligands that raise the energy of the filled Cu d z 2 orbital foster a preference for end-on binding as this is the only mode that permits good overlap with the in-plane O 2 π*. Because the overlap of Cu d z 2 with O 2 π* is reduced as compared to the overlap of Cu d xz with the same O 2 orbital, the resonance is also reduced, leading to generally more stable triplet states relative to singlets in the end-on geometry as compared to the side-on geometry, where singlet ground states become more easily accessible once ligands are stronger donors. Biradical Cu(II)-O 2 superoxide character in the electronic structure of the supported complexes leads to significant challenges for accurate quantum chemical calculations that are best addressed by exploiting the spin-purified M06L local density functional, single-reference completely renormalized coupled-cluster theory, or multireference second-order perturbation theory, all of which provide predictions that are qualitatively and quantitatively consistent with one another.

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“…The superoxide nature of this complex was experimentally determined from its v O-O frequency (1,043 cm Ϫ1 ) and 18 O isotope shift (⌬v ϭ 59 cm Ϫ1 ) (Fig. 4D) (15,20 Fig. 4B).…”

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O ₂ activation by binuclear Cu sites: Noncoupled versus exchange coupled reaction mechanisms

Chen

Solomon

2004

Proc. Natl. Acad. Sci. U.S.A.

160

146

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Binuclear Cu proteins play vital roles in O2 binding and activation in biology and can be classified into coupled and noncoupled binuclear sites based on the magnetic interaction between the two Cu centers. Coupled binuclear Cu proteins include hemocyanin, tyrosinase, and catechol oxidase. These proteins have two Cu centers strongly magnetically coupled through direct bridging ligands that provide a mechanism for the 2-electron reduction of O2 to a -2 : 2 side-on peroxide bridged Cu II 2 (O 2 2؊ ) species. This side-on bridged peroxo-Cu 2 II species is activated for electrophilic attack on the phenolic ring of substrates. Noncoupled binuclear Cu proteins include peptidylglycine ␣-hydroxylating monooxygenase and dopamine ␤-monooxygenase. These proteins have binuclear Cu active sites that are distant, that exhibit no exchange interaction, and that activate O2 at a single Cu center to generate a reactive Cu II ͞O2 species for H-atom abstraction from the C-H bond of substrates. O2 intermediates in the coupled binuclear Cu enzymes can be trapped and studied spectroscopically. Possible intermediates in noncoupled binuclear Cu proteins can be defined through correlation to mononuclear Cu II ͞O2 model complexes. The different intermediates in these two classes of binuclear Cu proteins exhibit different reactivities that correlate with their different electronic structures and exchange coupling interactions between the binuclear Cu centers. These studies provide insight into the role of exchange coupling between the Cu centers in their reaction mechanisms.

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A Monomeric Side-On Superoxocopper(II) Complex: Cu(O2)(HB(3-tBu-5-iPrpz)3)

Cited by 274 publications

References 1 publication

How useful are vibrational frequencies of isotopomeric O2 fragments for assessing local symmetry? Some simple systems and the vexing case of a galactose oxidase model

How useful are vibrational frequencies of isotopomeric O2 fragments for assessing local symmetry? Some simple systems and the vexing case of a galactose oxidase model

Stereoelectronic Effects on Molecular Geometries and State-Energy Splittings of Ligated Monocopper Dioxygen Complexes

O ₂ activation by binuclear Cu sites: Noncoupled versus exchange coupled reaction mechanisms

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A Monomeric Side-On Superoxocopper(II) Complex: Cu(O2)(HB(3-tBu-5-iPrpz)3)

Cited by 274 publications

References 1 publication

How useful are vibrational frequencies of isotopomeric O2 fragments for assessing local symmetry? Some simple systems and the vexing case of a galactose oxidase model

How useful are vibrational frequencies of isotopomeric O2 fragments for assessing local symmetry? Some simple systems and the vexing case of a galactose oxidase model

Stereoelectronic Effects on Molecular Geometries and State-Energy Splittings of Ligated Monocopper Dioxygen Complexes

O 2 activation by binuclear Cu sites: Noncoupled versus exchange coupled reaction mechanisms

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O ₂ activation by binuclear Cu sites: Noncoupled versus exchange coupled reaction mechanisms