Copper cryptand metal complexation

Macrobicyclic cascade cryptands have also been prepared such as the series of bis(tren) derived (tren = tris(2-aminoethyl) amine, see Section 4.4.3) compounds 5.9. The di-nickel(II) and di-copper(II) complexes of the cages with various spacers all bind a metal cation into each tren unit. These metal... 

The copper(II) chloride and cobalt(II) chloride complexes of 199 were prepared elemental analyses indicate that in both cases there are two metal associated with each cryptand. To date, however, no crystals suitable for X-ray structural determination studies have been obtained 149). 

The macrobicyclic cryptand BISTREN (3), as discussed earlier, binds anions when hexaprotonated. This compound is also capable of binding pairs of transition metal ions [e.g. the bis-copper(Il) Complex (55)] when unprotonated (39, 138). The bis-copper(II) based receptor (55) was observed to bind a chloride ion cascaded between the two metal ions. In fact, receptor 55 bound chloride more strongly (log K = 3.55) than the hexaprotonated form of 3 (log K = 2.36), and this was attributed to the formation of strong coordinate bonds. Hydroxide was also cascade bound forming a thermodynamically very stable complex (log K = 11.56), the resulting complex being of a different type from that formed by non-cryptate complexes of the Cu(II) ion. 

Macrobicyclic ligands incorporating heterocyclic subunits. Vogtle (58) and Newkome (59) have successfully prepared cryptands containing respectively one (58) and three (59) pyridine subunits in the macrobicyclic framework (Figure 2.18). The ligand (58) forms complexes with many metal cations, and binuclear cobalt and copper complexes of (59) were isolated. 

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