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Copper binuclear species

The roles of the copper enzymes in electron transport, oxygen transport, and oxidation reactions have guaranteed continued interest in their study. In addition to studies of the natural compounds, there have been many attempts to design model structures of these enzymes, particularly of the binuclear species. Many of these include both nitrogen and oxygen donors built into macrocyclic ligands, although sulfur has been used as well. ... [Pg.611]

Understanding of the proton translocation has been complicated by the need to address a steady-state circumstance rather than to consider static states. For example, in the oxidized state in the absence of reductant, the heme-copper binuclear center relaxes to a state that lies outside of the catalytic cycle. With proper consideration of the catalytic cycle according to Wikstrdm and Verkhovsky, Two protons each are pumped during the oxidative and reductive halves of the cycle. This important insight has yet to be carried to the molecular species involved, although an OH" ligand for Cub[II] has been considered, as well as earlier implication of a histidine liganded to Cub. ... [Pg.390]

Although the identity and nuclearity of active sites is still in debate, Cu-zeolite binuclear species are clearly reported as active sites. Nevertheless, it seems that the nature of the copper active site is strongly influenced by the reaction temperature and by the properties of the used zeolite. Indeed, over FAU zeolite, [CuOCu] dimer species are proposed to catalyze NH3-SCR reaction at low temperature (T < 300 °C) [128]. For NO decomposition, Moretti et al. [129, 130] also proposed that the main active sites over ZSM-5 (silica to alumina ratio from 66 to 80) consist of dimeric Cu species strongly anchored to next-nearest-neighbor framework AIO4 species. On the opposite, Cu " is suggested to become active at higher temperature (T > 350 °C) over NaY [131, 132]. [Pg.612]

In addition to the systems just mentioned, recent kinetic and mechanistic studies have included those involving copper(II) (409,410) and zinc(II) (411) species, various binuclear metal(II) complexes of first row transition elements (412-414), especially iron (407), cobalt (415), copper (305,416), and zinc (417,418), yttrium (419,420) and lanthanide (421,422) species, and thorium(IV) (423). [Pg.130]

The basic study was performed on copper complexes with N,N,N, N1-tetramethylethane-1,2-diamine (TMED), which were known to be very effective oxidative coupling catalysts (7,12). From our first kinetic studies it appeared that binuclear copper complexes are the active species as in some copper-containing enzymes. By applying the very strongly chelating TMED we were able to isolate crystals of the catalyst and to determine its structure by X-ray diffraction (13). Figure 1 shows this structure for the TMED complex of basic copper chloride Cu(0H)Cl prepared from CuCl by oxidation in moist pyridine. [Pg.10]

The current chapter focuses on the electrochemistry of the ionic forms of copper in solution, starting with the potentials of various copper species. This includes the effect of coordination geometry, donor atoms, and solvent upon the electrochemical potentials of copper redox couples, specifically Cu(II/I). This is followed by a discussion of the various types of coupled chemical reactions that may contribute to the observed Cu(II/I) electrochemical behavior and the characteristics that may be used to distinguish the presence of each of these mechanisms. The chapter concludes with brief discussions of the electrochemical properties of copper proteins, unidentate and binuclear complexes. [Pg.993]

Several diverse metal centres are involved in the catalysis of monooxygenation or hydroxylation reactions. The most important of these is cytochrome P-450, a hemoprotein with a cysteine residue as an axial ligand. Tyrosinase involves a coupled binuclear copper site, while dopamine jS-hydroxylase is also a copper protein but probably involves four binuclear copper sites, which are different from the tyrosinase sites. Putidamonooxin involves an iron-sulfur protein and a non-heme iron. In all cases a peroxo complex appears to be the active species. [Pg.709]

This protein contains a coupled binuclear copper site that appears to be very similar to that found in hemocyanin (Section 62.1.12.3.8).1399 Tyrosinase catalyzes the hydroxylation of monophenols, and also behaves as an oxidase in the oxidation of orfho-diphenols. The deoxy protein [copper(I)] binds dioxygen to give oxytyrosinase, which is a Cu11 peroxide species with antiferromagnetic coupling between the two Cu11 centres. The oxybinuclear site is diamagnetic to the most sensitive detectors. [Pg.711]

Finally, copper(I), silver(I), and mercury(II) triazenides react with selected rhodium(I), iridium(l), and platinum(II) halide complexes to afford metal-metal bonded binuclear triazenide-bridged species 129). [Pg.4]

One recombinant FetSp mutant is unique among multicopper oxidase species and has been particularly informative about the structure of the type 3 binuclear cluster in these species. This is the T1D/T2D double mutant that contains only this type 3 site (Blackburn et al., 2000). EXAFS analysis of this protein contains contributions from electron ejection and scattering from only the type 3 copper atoms and thus provides direct structural information about this cluster. The K-edge XAS spectrum for this mutant in its oxidized and reduced states is shown in Fig. 21. The oxidized sample has a nearly featureless edge with a midpoint energy of 8990 eV typical of tetragonally distorted type 2 Cu(ll) centers, i.e., those with predominantly histidine imidazole coordination. The reduced type 3 cluster exhibited a pronounced shoulder at 8984 eV just below the... [Pg.261]


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See also in sourсe #XX -- [ Pg.859 ]




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