Copper redox with complexes

Using 1,4,8,11-tetraazacyclotetradecane, the structure of complex (800) (distorted trigonal planar Cu-Cu 6.739 A) was determined. Reactivity with 02 was investigated to demonstrate the formation of trans-l,2-peroxo species.585 As part of their work with copper(I) complexes with 02, the structure of a dicopper(I) complex ((801) distorted tetrahedral 7.04 A), supported by macrocyclic ligand environment, was reported by Comba and co-workers. Tolman and co-workers structurally characterized a three-coordinate copper(I)-phenoxide complex (802) (planar T-shaped) that models the reduced form of GO.587 The copper(I) analogue [Cu(L)][CF3-SO3]-0.43MeOI I (803) of a copper(II) complex (534) was also reported to demonstrate the role of ligand framework conformability in CV /Cu1 redox potentials.434 Wilson and co-workers... 

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 (III)-Peptide Complexes. Molecular oxygen reacts with Cu(II)tetraglycine (G4) in neutral solution to produce a yellow species with an intense absorption band at 362 nm. As the oxygen in the solution is consumed, the amount of the yellow species decays (Figure 6). The uv-visible spectrum, molar absorptivity, dissociation kinetics in acid and in base, and the redox behavior of this yellow species are similar to those of Cunl(H.3G4)", which is generated by IrCl62 or by electrolytic oxidation of the corresponding Cu(II) complex. The peptide products after... 

From the known chemical properties of superoxide free radicals and hydrogen peroxide, it is unlikely that these two species will react directly with the range of biomolecules found in synovial fluid. It is more likely, particularly for superoxide radicals, that they will instead participate in redox reactions with complexes of metal ions such as iron and copper, although reaction with phenolic compounds cannot be excluded. It has been proposed therefore that synovial fluid, in particular hyaluronic acid, can be degraded in vivo through an iron-catalysed Haber-Weiss reaction. 

Another source of interest came from biochemistry. Research on the blue copper proteins revealed unusual electronic properties (redox potential and kinetics, EPR and optical behavior) that were suspected of arising from interaction of the copper ion with a thioether group from methionine [7]. While crystallographic studies established a weak interaction (Cu -- - S 2.9 A) [8,9,10], its influence on the electronic properties of the Cu site is now considered questionable. Nevertheless, the controversy regarding the blue eopper proteins, like the analogy to phosphines, served to focus attention on the broad issue of how thioether coordination affects the electronic structure of transition metal ions. Homoleptic thioether complexes provide the best way of assessing these consequences, since no other groups obscure the effect of thioether coordination. 

Mixed SAMs on gold electrodes from azido alkane thiols and various a>-functionalized alkanethiols were prepared. In the presence of copper(l) catalysts, these azide-modified surfaces are shown to react rapidly and quantitatively with terminal acetylenes forming 1,2,3-triazoles via click chemistry (Figure 6). In this way, thiol SAMs have been modified with complex functional molecules such as single-stranded DNA, porphyrin redox catalysts, and receptors for gold nanoparticles and other materials. 

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