Copper complex anion hosts

The complexation of anionic species by tetra-bridged phosphorylated cavitands concerns mainly the work of Puddephatt et al. who described the selective complexation of halides by the tetra-copper and tetra-silver complexes of 2 (see Scheme 17). The complexes are size selective hosts for halide anions and it was demonstrated that in the copper complex, iodide is preferred over chloride. Iodide is large enough to bridge the four copper atoms but chloride is too small and can coordinate only to three of them to form the [2-Cu4(yU-Cl)4(yU3-Cl)] complex so that in a mixed iodide-chloride complex, iodide is preferentially encapsulated inside the cavity. In the [2-Ag4(//-Cl)4(yU4-Cl)] silver complex, the larger size of the Ag(I) atom allowed the inner chloride atom to bind with the four silver atoms. The X-ray crystal structure of the complexes revealed that one Y halide ion is encapsulated in the center of the cavity and bound to 3 copper atoms in [2-Cu4(//-Cl)4(//3-Cl)] (Y=C1) [45] or to 4 copper atoms in [2-Cu4(/U-Cl)4(/U4-I)] (Y=I) and to 4 silver atoms in [2-Ag4(/i-Cl)4(/i4-Cl)] [47]. NMR studies in solution of the inclusion process showed that multiple coordination types take place in the supramolecular complexes. 

V=9.267(1) nm, Z=4, Ri=0.0S3 and Rw=0,058. The complex is composed of copper cations, nitrate anions, 1,10-phenanthroline, protocatechuic acid and lattice water molecules. The structure of H3PCA, N03 and waters comprises packing of three-dimensional network by hydrogen bonds with cavities. The complex can be considered as a model of host/guest supermolecule. The three-dimensional hydrogen-bonding network is the host species. The Cu(phen)3 cations, guest species, occupy the cavities of the host. 

A structural study of receptors 51, 52, and 49, showed three different modes of azide complexation to the binuclear copper(II) host (123) 1,1 cascaded, 1,3 cascaded, and noncascaded, respectively. These structures indicate that the nature of the macrocyclic framework of the receptor is important in determining the mode of anion coordination. Figure 5(a and b) shows the crystal structures of 52, 2 Cu(II)-azide, and 52, 2Cu(II)-chloride, respectively, for comparison (129). As can be seen, it is the length of the azide bridge that makes cascade complexation possible, whereas for the smaller mononuclear chloride anion this obviously cannot occur. Receptor 49 has also been shown to cascade bind pyrophosphate [as its bis-copper(II) complex] (130) and sulfate [as its bis-iron(II) complex](131). At about the same time, Nelson and co-workers (132) published a similar bis-copper(II) complex structure that cascaded an azide anion. 

In Equation 9.13, Zi, and Z2 are the number of electrons involved for redox Reaction 9.1 and 9.2, respectively, and F is Faraday s constant. If AG is negative then the oxidized form, Ox], will be reduced by the reductant, Red2. As an example, Pt can be readily deposited onto Cu surfaces and onto Au [97]. Deposition of Pt onto pre-reduced Ru surfaces has also been carried out using flic same principles. Similarly, Ru has been deposited onto Cu surfaces, but to a smaller extent than Pt and Au. This is in fact seen experimentally, by preferential Ru deposition onto the rims of copper particles [97]. The equilibrium potentials, Ei and E2, are given by the metal and metal-salt involved, as defined by Nemst s law. It follows that the anion of the metal salt influences the E value and hence, AG. Through the selection of proper complexing ions it is possible to reverse the host and depositing metals. This has been shown for Pd deposition onto Rh surfaces... 

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