Copper complexes mononuclear

Ascorbate Oxidase. The enzyme catalyzes the oxidation of ascorbate to dihydroascorbate and water by O2 and contains three types of copper complexes mononuclear Cu (I) and Cu II) and binuclear [Cu ]2 (HI). The redox potential of the primary electron acceptor of Cu l) Eo = 500 mV, which is quite sufficient for the one electron oxidation of ascorbate (Eo = 310 mV) but is not enough for the one-electron reduction of O2 (Eo = -330 mV). The most probable mechanism of reaction involves two consecutive one-electron reduction of the copper complexes followed by the two-electron reduction of O2 in the binuclear [Cu+(III)]2 complex accompanied by synchronuos proton transfer. 

Nickel atoms have also been allowed to react with C2H4 under cryogenic conditions (101,123). Depending on the metal-concentration conditions and the deposition temperature, either mononuclear species, Ni(C2H4) , n = 1-3(123), or multinuclear species, Ni2(C2H4) ,m = 1-2, and Ni3(CjH4)i, may be isolated. Unlike the copper complexes, these species are all colorless the mononuclear ethylene complexes each dis-... 

Calixarenes, when in their cone-conformation (54), represent versatile host systems for metalated container molecules and many examples have been reported in the literature (55-61). Reinaud and coworkers have carried out extensive work concerned with calix[6]arenes that are functionalized at the small rim by nitrogen arms (62), aiming to reproduce the hydro-phobic binding site of mononuclear zinc and copper metalloen-zymes. A recent example is the calix[6]arene ligand L1 (Fig. 3), in which a tris(2-methylpyridyl)amine unit covalently caps the calixarene small rim (63). The ligand forms copper complexes of... 

Cai et al. (71) examined the use of dinuclear copper complexes as catalysts in the cyclopropanation reaction. Their ligand design, based on the success exhibited by the Aratani system, incorporates a diimine aryloxide. A comparison of the mononuclear catalyst 99 with the corresponding dinuclear catalyst 100 showed certain modest benefits conferred by the latter, Eq. 52. The authors note that these catalysts are effective at ambient temperature but isolated yields are higher at 50°C with no loss in enantioselectivity. 

Hathaway has attempted to assess the value of the electronic properties of polycrystalline mononuclear copper complexes with the [CUN4], [CuNj], and [CuN ] chromophores of unknown crystal structure, in predicting the stereochemical environment of the copper(ii) atom. The value of having B. J. Hathaway, J.C.5. Dalton, 1972, 1196. 

Uniquely, the Cu +-neomycin B system has been shown to form two-centered copper complexes at pH values below 6.5 if the metal ion is present in excess (Table 8.3) with less than 15% (relative to total Cu + present) of mononuclear species detected at pH values in the range of 4 to 6. At a 2 1 Cu + neomycin B stoichiometric ratio it was shown that only the dinuclear species exists in solution at pH 7.5. The second binding site in the dinuclear complex was proposed to be in ring D, however, this unique feature is only observed in the case of the copper complex of neomycin B. 

Figure 2.16 The redox-driven disassembling of a dicopper(I) double-strand helicate complex to give two mononuclear copper(II) complexes, in which each strand behaves as a quadridentate ligand. On subsequent reduction, the two mononuclear complexes reassemble to give the helicate. The illustrated process fits well the behavior of copper complexes of 16 in a MeCN solution.

The other copper-only binuclear centre to be considered is the CuA or purple copper complex. It is part of the terminal oxidase in mitochondrial respiration, cytochrome c oxidase (COX). Its EPR signature, a seven-line spectrum, has since long been known to be different from the classes type 1 to 3 and arises from two copper ions in a 1.5 valence (or mixed valence) state, first proposed from EPR-analysis of a similar center in nitrous oxide (N20) reductase. There is a close correspondence between the blue and purple states of copper since each of the two copper ions in CuA can be considered as being structurally related to the mononuclear blue site coordination. 

Table 6 Copper(I) Mononuclear Three-coordinate Complexes...

Table 8 Average Cu—L Distances (A) for Copper(I) Mononuclear Complexes as a Function of Coordination...

Platinum complexes (continued) with aryls, thallium adducts, 3, 399 with bis(alkynyl), NLO properties, 12, 125 with bisalkynyl copper complexes, 2, 182-186 with bis(3,5-dichloro-2,4,6-trifluorophenyl), 8, 483 and C-F bond activation, 1, 743 in C-H bond alkenylations, 10, 225 in C-H bond electrophilic activation studies, 1, 707 with chromium, 5, 312 with copper, 2, 168 cyclometallated, for OLEDs, 12, 145 in diyne carbometallations, 10, 351-352 in ene-yne metathesis, 11, 273 in enyne skeletal reorganization, 11, 289 heteronuclear Pt isocyanides, 8, 431 inside metallodendrimers, 12, 400 kinetic studies, 1, 531 on metallodendrimer surfaces, 12, 391 mononuclear Pt(II) isocyanides, 8, 428 mononuclear Pt(0) isocyanides, 8, 424 overview, 8, 405-444 d -cP oxidative addition, PHIP, 1, 436 polynuclear Pt isocyanides, 8, 431 polynuclear Pt(0) isocyanides, 8, 425 Pt(I) isocyanides, 8, 425 Pt(IV) isocyanides, 8, 430... 

Additional information on the nature of copper complexes formed on the Ti02 surface and their relative amount has been obtained in [285]. Fig. 8.18 represents typical EPR spectra of Cu2+ ions adsorbed onto Ti02 nanoparticles at pH 3.1 and 6.0. At pH 3.1, the spectrum is typical of isolated mononuclear Cu(II) complexes. Some noticeable broadening of the ESR lines corresponding to the parallel orientation of Cu(II) complexes in the external magnetic field, which is observed even for the most magnetically diluted samples, is indicative of the existence of several paramagnetic centers with similar, but not identical structures. The increase of Cu(II) concentration results initially in an increase of... 

The synthesis, structure, and superoxide dismutase mimetic activity in vitro and the protection against reactive oxygen species in vivo of mononuclear copper complexes with 2-(4-methylphenylsulfamoyl)-6-nitrobenzothiazole have been reported [602], Like 1,2,3-benzoxadiazoles, nitroderivatives of 1,2,3-benzothiadiazoles were obtained on diazotization of the corresponding or/Zzo-aminothiophcnolcs [213, 218, 583], The initial or/Zzo-thiophcnols for this reaction were synthesized by nucleophilic substitution of halogen in ort/zo-halogenoanilines. It turned out that 4-nitro- and... 

Galactose oxidase hinds a single copper ion within Domain 11 on the axis of the wheel. The active site (Fig. 5) is unhke any other biological copper complex, an appropriate distinction for this remarkable enzyme. To explore the site in more detail, the protein environment of the mononuclear copper center may be separated into (A) direcdy coordinated metal hgands (hrst shell, inner sphere interactions) and (B) the extended active site environment (the second shell or outer coordination sphere). 

There are many structural studies of copper coordination compounds with azide ligands, mainly of mononuclear and binuclear copper complexes but a few also of trinuclear copper complexes. A comprehensive... 

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