CuCO complexes

Chemical models for the speciation of Cu in freshwater (Millero, 1975) predict that free Cu (aq) is less than 1% of the total dissolved Cu and that Cu(C03)i and CuCO are equally important for the average river water. Leckie and Davis (1979) showed that the CuCO complex is the most important one near the neutral pH. At pH values above 8, the dihydroxo-Copper(ll) complex predominates. The chemical form of Cu is critical to the behavior of the element in geochemical and biological processes (Leckie and Davis, 1979). Cupric Cu forms strong complexes with many organic compounds. 

Barone, V., 1994, Validation of Self-Consistent Hybrid Approaches for the Study of Transition Metal Complexes. NiCO and CuCO as Case Studies , Chem. Phys. Lett., 233, 129. 

The aqua Zn ion is dominant in organic matter-free freshwater while the free Zrf+ ion and chloride complexes dominate in seawater (Stanley and Byrne 1990 Millero 1996). The free Cu + ion is dominant in freshwater, while the carbonate complexes CuCO, and [Cu(C03)2] are preponderant in seawater. Speciation and solubility of Zn in Cl-rich hydrothermal solutions has been investigated by Wesolowski et al. (1998). Speciation and solubility of Cu have been investigated by Mountain and Seward (1999) for hydrothermal solutions dominated by sulfides and by Xiao et al. (1998), Liu et al. (2002), and Archibald et al. (2002) for solutions dominated by chlorides. 

Mixed crystals of type II have been used in the form of thin films on electrodes as well as in the form of chemically synthesized powders immobilized on electrodes. Depending on the radii of the ions involved in the synthesis, solid solutions can also be formed as single phases. In the case of K CuCo[Fe(CN)(5] films, XRD results indicated that a single phase with a cubic face-centered symmetry was formed [31]. The situation is more complex in the case of K NiPd[Fe(CN)6] deposited as a thin film on electrodes [32]. Kulesza etal. have pointed out that there is a critical concentration of Pd + below which Pd + was taken as the countercation at interstitial position, while above that value a solid solution is formed in which both Ni " " and Pd + are nitrogen coordinated. 

The controlled demetallation of CuCu.lO by potassium cyanide at room temperature afforded the mononuclear complex Cu.lO containing a vacant site ready for coordination. Addition of the appropriate salt (AgBp4 or Co(BF4)2) to Cu.lO leads to the heterodinuclear [3]catenates CuAg.lO and CuCo.lO for which the specific electrochemical properties [48] were studied and compared to those of their monometallic analogues, namely M.5"+ (Table 5). 

As expected, the redox potential of the Cu +/Cu+ couple is slightly shifted towards anodic values in CuAg.l0 + as compared to Cu.S" ". This effect is even more pronounced in CuCo.l0 + the copper(II) state is significantly more difficult to electro-generate than for the mono-nuclear species Cu.5+. The positive shift of the Cu +/Cu+ redox potential in di-metallic species as compared to Cu.5+ shows that the two metal complex subunits of the [3]catenates do interact. This may reflect an... 

Finally, the CuCo.l0 + catenate does not luminesce under any condition, showing that the potentially luminescent MLCT level of the Cu-complexed moiety is quenched by the Co-based one. A possible quenching mechanism is energy transfer, since the d Co + metal ion has low-energy d-d levels (<10 000 cm ) [65], but also electron transfer is thermodynamically allowed (AG = -0.54 eV). 

Assume similar to CuCO" and oxalate complexation of divalent metals. 

The toxicity and bioavailability of metals in natural waters depends on the aqueous speciation or complexation of those metals. The toxicities to aquatic life of Cu +, Cd, Zn, Ni, Hg ", and Pb are a function of the activities of the metal ions and their complexes, not of total metal concentrations (cf. Morel and Hering 1993 Manahan 1994). For example, monomethyl mercury ion (CH3Hg ) and Cu are toxic to fish, but some other Hg and Cu complexes (such as CuCO ) are far less so. The bioavailability of essential metals such as Fe, Mn, Zn, and Cu to plants is also a function of their metal speciation (Morel and Hering 1993). Until recently the U.S. Environmental Protection Agency did not recognize the importance of metal speciation in its water quality assessments (cf. Hall and Raider 1993). Metal toxicity is considered briefly near the end of this chapter. 

To start with, we consider the complex CuCo(fsa)2en(H20)2 H20, noted [CuCo], of which the structure is very similar to that shown in Fig. 15, Co(II) replacing Ni(II) in the octahedral site851. This system may be viewed as the simplest one involving an orbital degeneracy since only one ion is orbitally degenerate, the other ion being a spin doublet1201. 

Sample Copper added pg/liter pH HCOr mmole/liter Hardness, mg/llter as CaCOj Cu CuCO) Amino Inert Acid Humic Complex Complex Hexanol Extractable Cyanide complex, etc. 

The reaction is potentially important because the complex absorbs significantly above 300nm and CuCO is the major inorganic copper complex in seawater (12). Cu(I) production was extremely slow, negligible in sunlight and probably not significant in the environment. The low quantum yield may 1 due to back reaction of Cu with CO-, although addition of 10 mol L 2-propanol to react with the CO radical did not lead to an increase In rate. 

This mechanism Is consistent with expectations from charge transfer theory which Indicates that the rate of the charge transfer step Is proportional to the free energy change on going from the Cu(II) complex to the Cu(I) complex Reduction of CuClOH leads, o formation of the very stable CuClOH species. Reduction of Cu. . or CuCO. does not lead to direct formation of a stable... 

Many of the minerals in the Earth s crust are not simple ionic compounds consisting of one type of cation such as Cu and one type of anion such as carbonate, COs ". These more complex compounds can be classified as double (or triple or quadruple) salts. (These salts are also referred to as ternary or quaternary.) That is, they contain more than one type of cation and/or more than one type of anion. For example, one of the conunon ores of copper is malachite, which has the formula Cu2C03(0H)2. This is an ionic compound that contains the Cu " ion and both the carbonate and hydroxide anions. Double salts can be thought of as combinations (but not mixtmes) of two or more simple salts. Malachite can be visualized as CuCOs -1- Cu(OH)2. Malachite is frequently found with azurite, which has the formula Cu3(C03)2(0H)2. Azurite simply has a different ratio of the two simple salts 2 CuCOs + Cu(OH)2. 

The luminescence properties of a 3-catenand (20) and related 3-catenates containing a copper(I) center [Cu 20]+ were reported in 1991 [96]. The photophysical data are summarized in Table 5. It is interesting to note that while the mononuclear [Cu 20]+ shows ligand-centered tctc, and MLCT emission, the dinuclear complex [Cu2 20] + only reveals a single MLCT phosphorescence band at 700 nm in CH2CI2. The mixed-metal complex [CuCo 20] + is not lumi-... 

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