X-ray Absorption Spectroscopic Studies of the Copper(I) Complexes of Crown Ether Appended Bis{(2-pyridyl)ethyl}amines and Their Dioxygen Adducts.
An X-ray absorption spectroscopic study of the Cu complexes of the bis{(2-pyridyl)ethyl}-appended monoaza crown ether 1, diaza crown ether 2, and diphenylglycoluril diaza basket 3 is reported. Following detailed analysis of the spectra of the crystallographically characterized model compound tetrapyridyl Cu(II) bis(nitrato pyridine) (4), the contributions of the ring atoms of the coordinating pyridine to the EXAFS were simulated using a multiple-scattering approach and the final parameters obtained by restrained refinement. Oxygenation of the Cu(I) complexes resulted in a large increase of the intensity of the major peak in the phase-corrected Fourier transform. This was interpreted as evidence for a &mgr;-eta(2):eta(2)-peroxo coordination mode of the oxygen between the copper ions, which had changed valence from Cu(I) to Cu(II) as judged from the edge position. This oxygen binding mode is reminiscent of that of hemocyanin, but the Cu-Cu distances are significantly shorter in the model than in the enzyme and vary with solvent. The EXAFS of the oxygenated complexes was simulated in a new approach in which, besides the parameters of the pyridine unit, those of an additional multiple scattering unit describing the geometry of the Cu-O(2)-Cu moiety were also refined.
Feiters
Martinus C.
MC
Department of Organic Chemistry, NSR Center, University of Nijmegen, Toernooiveld, NL-6525 ED Nijmegen, The Netherlands, EMBL Outstation at DESY, Notkestrasse 85, 22603 Hamburg, Germany, and Department of Chemistry, Johns Hopkins University, Charles & 34th Streets, Baltimore, Maryland 21218.
Gebbink
Robertus J. M. Klein
RJ
Solé
V. Armando
VA
Nolting
Hans-Friedrich
HF
Karlin
Kenneth D.
KD
Nolte
Roeland J. M.
RJ