Copper(I) Complex O(2)-Reactivity With a N(3)S Thioether Ligand: a Copper-Dioxygen Adduct Including Sulfur Ligation, Ligand Oxygenation, And Comparisons With All Nitrogen Ligand Analogues
In order to contribute to an understanding of the effects of thioether sulfur ligation in copper-O(2) reactivity, the tetradentate ligands L(N3S) (2-ethylthio-N,N-bis(pyridin-2-yl)methylethanamine) and L(N3S')(2-ethylthio-N,N-bis(pyridin-2-yl)ethylethanamine) have been synthesized. Corresponding copper(I) complexes, [CuI(L(N3S))]ClO(4) (1-ClO(4)), [CuI(L(N3S))]B(C(6)F(5))(4) (1-B(C(6)F(5))(4)), and [CuI(L(N3S'))]ClO(4) (2), were generated, and their redox properties, CO binding, and O(2)-reactivity were compared to the situation with analogous compounds having all nitrogen donor ligands, [CuI(TMPA)(MeCN)](+) and [Cu(I)(PMAP)](+) (TMPA = tris(2-pyridylmethyl)amine; PMAP = bis[2-(2-pyridyl)ethyl]-(2-pyridyl)methylamine). X-ray structures of 1-B(C(6)F(5))(4), a dimer, and copper(II) complex [Cu(II)(L(N3S))(MeOH)](ClO(4))(2) (3) were obtained; the latter possesses axial thioether coordination. At low temperature in CH(2)Cl(2), acetone, or 2-methyltetrahydrofuran (MeTHF), 1 reacts with O(2) and generates an adduct formulated as an end-on peroxodicopper(II) complex [{l_brace}Cu(II)(L(N3S)){r_brace}(2)(mu-1,2-O(2)(2-))](2+) (4){lambda}(max) = 530 (epsilon approximately 9200 M(-1) cm(-1)) and 605 nm (epsilon approximately 11,800 M(-1) cm(-1)); the number and relative intensity of LMCT UV-vis bands vary from those for [{l_brace}Cu(II)(TMPA){r_brace}(2)(O(2)(2-))](2+) {lambda}(max) = 524 nm (epsilon = 11,300 M(-1) cm(-1)) and 615 nm (epsilon = 5800 M(-1) cm(-1)) and are ascribed to electronic structure variation due to coordination geometry changes with the L(N3S) ligand. Resonance Raman spectroscopy confirms the end-on peroxo-formulation {nu}(O-O) = 817 cm(-1) (16-18O(2) Delta = 46 cm(-1)) and nu(Cu-O) = 545 cm(-1) (16-18O(2) Delta = 26 cm(-1)); these values are lower in energy than those for [{l_brace}Cu(II)(TMPA){r_brace}(2)(O(2)(2-))](2+) {nu}(Cu-O) = 561 cm(-1) and nu(O-O) = 827 cm(-1) and can be attributed to less electron density donation from the peroxide pi* orbitals to the Cu(II) ion. Complex 4 is the first copper-dioxygen adduct with thioether ligation; direct evidence comes from EXAFS spectroscopy {l_brace}Cu K-edge; Cu-S = 2.4 Angstrom{r_brace}. Following a [Cu(I)(L(N3S))](+)/O(2) reaction and warming, the L(N3S) thioether ligand is oxidized to the sulfoxide in a reaction modeling copper monooxygenase activity. By contrast, 2 is unreactive toward dioxygen probably due to its significantly increased Cu(II)/Cu(I) redox potential, an effect of ligand chelate ring size (in comparison to 1). Discussion of the relevance of the chemistry to copper enzyme O(2)-activation, and situations of biological stress involving methionine oxidation, is provided.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-76SF00515
- OSTI ID:
- 953935
- Report Number(s):
- SLAC-REPRINT-2009-457; INOCAJ; TRN: US201004%%672
- Journal Information:
- Inorg. Chem. 46:6056,2007, Vol. 46, Issue 15; ISSN 0020-1669
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ACETONE
ADDUCTS
BIOLOGICAL STRESS
CHELATES
CHEMISTRY
COPPER COMPLEXES
COPPER
ELECTRON DENSITY
ELECTRONIC STRUCTURE
ENZYMES
LIGANDS
METHIONINE
NITROGEN
ORGANIC SULFUR COMPOUNDS
OXIDATION
PEROXIDES
RAMAN SPECTROSCOPY
REACTIVITY
REDOX POTENTIAL
RESONANCE
SIMULATION
SPECTROSCOPY
SULFOXIDES
SULFUR
TEMPERATURE RANGE 0065-0273 K
VARIATIONS
Other
OTHER
CHEM