Reactions of Dioxygen (O2) with Mononuclear Copper(I) Complexes: Temperature-Dependent Formation of Peroxo- or Oxo- (and Dihydroxo-) Bridged Dicopper(II) Complexes

Indrajit Sanyal, Mohammad Tahir Mahroof, M. Sarwar Nasir, Phalguni Ghosh, Brett I. Cohen, Yilma Gultneh, Richard W. Cruse, Amjad Farooq, Kenneth D. Karlin, Shuncheng Liu, Jon Zubieta

Research output: Contribution to journalArticle

139 Scopus citations

Abstract

The binding of O2 to copper(I) and its subsequent reactivity is important in a variety of chemical and biological processes. We previously studied functional models of hemocyanins (arthropodal and molluscan O2 carriers) involving a class of O2 adducts [Cu2(Nn)(O2)]2+ (2) (Karlin, K. D.; et al. Inorg. Chem. 1992, 31, 1436-1451), where Nn are dinucleating ligands which employ two tridentate bis(2-pyridylethyl)amine (PY2) moieties, connected by a variable alkyl chain. Here, we report studies of O2 reactivity using R-substituted PY2 tridentate ligands and derived mononuclear Cu(I) precursor complexes [Cu(RPY2)]+ (3a, R = Me; 3b, R = PhCH2; 3c, R = Ph). The X-ray structure of the nearly “T-shaped” complex 3c(PF6) (C20H21CuN3F6P) is reported; it crystallizes in the space group P21/n, a = 10.037 (4) Å, b = 14.406 (4) Å, c = 15.210 (5) Å, β = 105.99 (3)°, Dcalcd = 1.61 g/cm3, Z = 4. Electrochemical studies indicate reversible one-electron oxidations in DMF, with E1/2 values varying between +80 and +150 mV vs NHE, depending on R. Above 0 °C, complexes 3 react with O2 in a stoichiometry of Cu/O2 = 4:1 (manometry) giving oxo-bridged dicopper(II) products [Cu2(RPY2)2(0)]2+ (4). EPR spectra are consistent with the bridged dinuclear formulation; i.e., 4a, c are EPR silent while 4b exhibits a typical “half-field” (g = 4) line in CH2C12. In methanol, the complexes break up and exhibit normal tetragonal spectra. Oxo complexes 4 react with water (reversibly, for 4a, b) to give dihydroxo-bridged complexes [Cu2(RPY2)2(OH)2]2+ (5), with “parallel-planar” structures; EPR spectroscopic and other physical measurements are consistent. However, low-temperature (-80 °C) oxygenation of complexes 3 results in the formation of O2 adducts [Cu2(RPY2)2(O2)]2+ (6), as indicated by manometry (Cu/O2 = 2:1) and EPR (“silent”) and UV-vis (i.e., strong 350-360-nm absorption) spectroscopies. The latter indicates a close similarity of these complexes to 2, with their proposed bent (μ-n2:n2-peroxo)dicopper(II) structures. Prolonged exposure of [Cu(PhCH2PY2)]+ (3b) to O2 causes a novel N-dealkylation reaction, with oxidative cleavage of the ligand producing H-PY2 and benzaldehyde (20% yield). Isotope labeling studies reveal that the source of oxygen in the PhCHO product is O2. The relationship of the chemistry presented here to other copper-dioxygen chemistry and copper proteins is discussed.

Original languageEnglish (US)
Pages (from-to)4322-4332
Number of pages11
JournalInorganic Chemistry
Volume31
Issue number21
DOIs
StatePublished - Jan 1 1992

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Fingerprint Dive into the research topics of 'Reactions of Dioxygen (O<sub>2</sub>) with Mononuclear Copper(I) Complexes: Temperature-Dependent Formation of Peroxo- or Oxo- (and Dihydroxo-) Bridged Dicopper(II) Complexes'. Together they form a unique fingerprint.

  • Cite this

    Sanyal, I., Mahroof, M. T., Nasir, M. S., Ghosh, P., Cohen, B. I., Gultneh, Y., Cruse, R. W., Farooq, A., Karlin, K. D., Liu, S., & Zubieta, J. (1992). Reactions of Dioxygen (O2) with Mononuclear Copper(I) Complexes: Temperature-Dependent Formation of Peroxo- or Oxo- (and Dihydroxo-) Bridged Dicopper(II) Complexes. Inorganic Chemistry, 31(21), 4322-4332. https://doi.org/10.1021/ic00047a020