Copper model compounds

Riley MJ (2001) Geometric and Electronic Information From the Spectroscopy of Six-Coordinate Copper(II) Compounds. 214 57-80 Rissanen K, see Nummelin S (2000) 210 1 -67 Roeggen I (1999) Extended Geminal Models. 205 89-103... 

In an elegant approach, Comba and co-workers initiated molecular-mechanics-based models that allow the rational design of ligand systems which are able to stabilize copper-dioxygen compounds. As a part of this investigation, complexes (241) (r = 0.12),223 (242) (r = 0.31),224 and (243) (r = 0.85)224 were synthesized and the reactivity of copper(I) complexes (Section 6.6.4.2.2(iv)) with dioxygen was investigated. 

Model systems for Type I copper proteins structures of copper coordination compounds with thioether and azole-containing ligands.17... 

The higher coordinating ability and Lewis acidity of Zn(H) ion in addition to the low pK of the metal-bound water molecule and the appearance of this metal ion in native phosphatases inspired a number of research groups to develop Zn(II)-containing dinuclear artificial phosphatases. In contrast, very few model compounds have been published to mimic the activity of Fe(III) ion in dinuclear centers of phosphatase enzymes. Cu(II) or lanthanide ions are not relevant to natural systems but their chemical properties in certain cases allow extraordinarily high acceleration of phosphate-ester hydrolysis [as much as 108 for copper(II) or 1013 for lanthanide(III) ions]. 

This discussion of copper-containing enzymes has focused on structure and function information for Type I blue copper proteins azurin and plastocyanin, Type III hemocyanin, and Type II superoxide dismutase s structure and mechanism of activity. Information on spectral properties for some metalloproteins and their model compounds has been included in Tables 5.2, 5.3, and 5.7. One model system for Type I copper proteins39 and one for Type II centers40 have been discussed. Many others can be found in the literature. A more complete discussion, including mechanistic detail, about hemocyanin and tyrosinase model systems has been included. Models for the blue copper oxidases laccase and ascorbate oxidases have not been discussed. Students are referred to the references listed in the reference section for discussion of some other model systems. Many more are to be found in literature searches.50... 

In 1997, four laboratories reported their results on (phenoxyl)copper(II) structural model compounds that stressed various aspects of the coordination chemistry of GO and glyoxal oxidase in its various oxidation levels. 

The d-d spectra of copper(II) compounds have provided a fruitful field for practitioners of the AOM. A wealth of structural data is available, and a rich variety of coordination geometries has been revealed. If we can make allowance for the dependence of the AOM parameters on the intemuclear distance, we are provided with excellent opportunities to test the validity of AOM parameters over a range of related systems. However, the progress of such studies over the years has illustrated the fact that a simple model may be very successful in explaining a limited amount of dubious experimental data as more crystal structures appear and as better spectroscopic data become available, the simple model may require considerable refurbishment, perhaps to the extent that it loses some of its appeal and utility. 

Figure 7.48 Two cytochrome c oxidase Cua center model compounds (A) delocalized core with two i-l,3-(KN KO)-ureate bridges as reported in reference 165-and (B) a dithiolate-bridged mixed-valence binuclear copper ion complex as re in reference 166.

The ability of peptides CBPOl-GBP 18 to modulate pyridoxamine-mediated transamination was determined by the conversion of pyruvic acid to alanine in both the absence and presence of copper(II) ion, which would be coordinated by the transamination intermediates [32]. In the absence of copper(II) ion,peptide CBP13 showed up to a 5.6-fold increase in alanine production relative to a pyridoxamine model compound and peptide CBP14 produced alanine with a 27% ee of the 1-enantiomer. In the presence of copper(II) ion, peptide CBP13 again showed the greatest increase in product production, with a 31.7-fold increase in alanine production relative to the pyridoxamine model compound. Peptide CBPIO showed optical induction for D-alanine with a 37% ee. 

The polymerization of halophenoxides by copper (II) mediated halide displacement is a mechanistically complicated reaction. Elucidation of the structure of the polymers is essential to an understanding of both the polymerization chemistry and the peculiar physical properties of the polymers. The physical tool which has yielded most information on the polymer structure is nmr. The first conclusion which derives from a study of the spectra of poly(dihalophenyleneoxides) is that regioselectivity in halogen displacement is more likely the source of the polymer properties than branching. A more rigorous confirmation of the polymer structures will depend on a detailed analysis of the spectra of model compounds for the chain segments. 

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