Double helical coordination metal compounds

The reactions of LnCla (Ln = lanthanide cations), 1-(S,S) or d-(R,R)-tartaric acid and molybdate in acidified aqueous solutions gave rise to enantio-pure left-or right-handed double helical coordination metal compounds. TG and powder XRD studies suggested that the backbone collapses with the removal of aqua ligands. However, it reverts easily to the original compound after being... 

Section 9.7). Our work involved first the self-assembly of double-helical metal complexes. This particularly interesting case of self-assembly of a coordination compound represented a first step in our studies on the design of inorganic programmed systems. 

Formation of [6 + 6] double helicates is possible, however, if terdentate metal binding domains are used. A six-coordinate metal ion may thus bind to one domain from each helicand ligand. The simplest example of such a ligand is the attractively named 2,2, 6, 2" 6",2" 6", 2"" 6"",2 ""-sexipyridine (10.120). In the presence of a wide variety of metal ions such as Cd2+, Fe2+, Co2+, Ni2+ and Cu2+ a double helical 2 2 complex is formed. The X-ray molecular structure of the cadmium compound is shown in Figure 10.78.85... 

There are many examples of compounds, usually short polymers, that spontaneously form double helical structures. A classic example involves a number of bipyridyl ligands joined by short, flexible spacers. In the presence of Cu(I), which has both an affinity for nitrogen-containing ligands and a preference for a tetrahedral disposition of donor atoms, discrete double helical complexes are formed [23], A similar phenomenon gives rise to a triple helical motif when a metal that preferentially adopts an octahedral coordination geometry is used [24],... 

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