Models for methemocyanin derivatives: Structural and spectroscopic comparisons of related azido-coordinated (N3 -) mono- and dinuclear copper(II) complexes

Kenneth D. Karlin, Brett I. Cohen, John C. Hayes, Amjad Farooq, Jon A Zubieta

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Abstract

The use of the azide (N3 -) ligand as a probe of the dinuclear copper active site in the dioxygen-transport protein hemocyanin has prompted us to synthesize model complexes that may shed light on the structural and spectroscopic features associated with N3 - binding to Cu(II) in well-defined chemical systems. We report the synthesis and structural and spectroscopic properties of N3 - bound to a dinuclear Cu(II) complex and a mononuclear analogue. The dinucleating ligand, L-OH, forms a phenoxo-bridged dicopper(II) complex, 2b, where each Cu(II) ion is also coordinated in a square-based-pyramidal geometry to the nitrogen atoms of a tridentate py2 unit (py2 = bis(2-(2-pyridyl)ethyl)amine) and to a μ-1,1-N3 - ligand. A mononucleating analogue, [CuII-(L′-O-)(N3 -)] (3b), contains Cu(II) coordinated to the same N3O donor set provided by L′-OH and a terminally coordinated N3 - ligand in a coordination environment very similar to that found in 2b. Compound 2b crystallizes in the triclinic space group P1 with Z = 2 and a = 9.583 (1) Å, b = 10.123 (2) Å, c = 23.758 (4) Å, α = 87.19 (1)°, β = 88.83 (1)°, and γ = 84.85 (1)°. Complex 3b crystallizes in the monoclinic space group P21/c, with Z = 4 and a = 9.529 (7) Å, b = 18.950 (2) Å, c = 13.829 (5) Å, and β = 109.38 (5)°. Comparisons of the charge-transfer (CT) features observed in UV-vis spectra of these complexes and related chloride and/or nitrate ion containing derivatives of L-OH, L′-OH, and py2 allow assignment of the PhO- → Cu(II) (450-460 nm) and/or N3 - → Cu(II) (370-405 nm) CT bands. Other structural and spectroscopic comparisons are also made.

Original languageEnglish (US)
Pages (from-to)147-153
Number of pages7
JournalInorganic Chemistry
Volume26
Issue number1
StatePublished - 1987
Externally publishedYes

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ASJC Scopus subject areas

  • Inorganic Chemistry

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