Copper couples redox properties

Copper(IV) complexes, 750 Coppet(IMII) couples redox properties, 749 Copper(II) ions hard acid, 594 Copper proteins, 720 nonblue, 723 type III, 724 Copper(II) systems biological, 720-729 Cytidine... 

Comba and co-workers described a simple and efficient method for the determination of solution structures of weakly coupled binuclear copper(II) complexes.54 The technique involves the combination of molecular mechanics55,56 and EPR spectroscopy. From this standpoint they reported the structure of the complex (29). Using an acyclic tertiary tetraamine ligand, Bernhardt reported57 crystal structure of the complex (30), along with its redox properties. 

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. 

Copper-proteins are wide-spread in both animals and plants and have been related to many metabolic processes, as oxygen transport, electron transfer and hydroxylation Copper-containing sites are usually classified in three different types " the type 1, or blue center is characterized by a combination of properties that has not yet been reproduced in model complexes (an intense absorption band at 600 nm, a very small copper hyperfine coupling constant A and a high positive redox potential for the Cu(II)/ Cu(I) couple) the type 2, or non-blue center has properties comparable to those of low molecular weight cupric complexes the type 3 consists of an antiferromagnetically coupled copper(II) pair. 

Copper(I) complexes catalyse a variety of organic reactions which are of synthetic and industrial importance.305 In such processes that involve halide abstraction from aryl or alkyl halides, the abstraction step by a Cu(I) catalyst is believed to be the rate-determining step. In order to circumvent the property of facile disproportionation of Cu, various methods of stabilising Cu(I) and influencing reaction rates were considered.306 A kinetics study of ligand (L) effects on the reactivity of Cu(I)L complexes towards C13CC02 was undertaken. The results indicated that the rate of the chlorine abstraction reaction was affected by several factors. These were the redox potential of the Cu(II/I)L couple, the hybridisation on Cu(I) in the Cu(I)L complex, steric hindrance, and electron density on the central Cu(I) cation at the binding site of the chlorine atom to be abstracted. The volume of activation,... 

Blue (Type 1) copper proteins are found widely in nature. Typical examples are plasiocyaiiin (MW 10,500) and ascorbale oxidase (MW 150,000) which contain one and eight Cu atoms per protein, respectively. The former serves as a component of the electron transfer chain in plant photosynthesis while the latter is an enzyme involved in the oxidation of ascorbic acid. The oxidized form is characterized by intense blue color due to electronic absorption near 600 nm. In addition, blue copper proteins exhibit unusual properties such as extremely small hyperfine splitting constants (0.003 0.009 cm" ) in ESR spectra and rather high redox potential (4-0.2 0.8 V) compared to the Cu(ll)/Cu(I) couple in aqueous solution. 

One of the important roles of metalloproteins is electron transport between functional molecules in biological systems [39], Copper proteins are involved in electron transfer, redox reactions and the transport and activation of dioxygen. They are classified into Types I, II and III, and eir properties are as follows Type I One copper is involved in one unit. The copper has a strong absorption around 600 nm and small hyperfine coupling constants in ESR. It is called Blue copper protein. 

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