Multidentate organic ligands

Two reviews5,6 with approximately 34 references discuss a coordination approach to three-dimensional assemblies via molecular paneling. Families of planar exo-multidentate organic ligands (molecular panels) assemble into large three-dimensional assemblies through metal-coordination. In particular, m-protected square planar metals, (en)Pd2+ or (en)Pt2+ (en = ethylene-1,2-diamine), are very useful to panel the molecules. Metal-assembled cages, bowls, tubes, capsules, and polyhedra are efficiently constructed by this approach. 

Figure 11.12. Multidentate organic ligands 7 and 8 (with cis and trans conformations) used in the construction of silver(I) tube-like complexes.

The formation constants of the proton and metal ion complexes of cyanide ion have been critically surveyed. The recommended value for pK . is correct, but the tentative values for higher ionic strengths seem to be erroneous [92BAN/BLI], Several literature values for the formation constants of Ni(CN)4 and Ni(CN)4 as well as reaction enthalpies for the formation of Ni(CN)4 were reported, but no recommended values were given. In addition, the formation constants of several NiX(CN)4 complexes (X = multidentate organic ligands,x= or 2) were listed. 

Metal complexes that have been treated with MM typically involve one metal and multidentate organic ligands. 

Huang et al. [167] used one H-carbon and one L-carbon (see Section II), with pH as the master variable and interpreted similar results in terms of the formation of surface complexes. They showed that Co(II) was removed by adsorption mechanism rather than precipitation, especially for the L-carbons. They proceeded to postulate the formation of specific multidentated Co(Il) complexes with surface hydroxo groups as ligands and analyzed the inhibiting or enhancing effect of several organic ligands. 

Multidentate macrocyclic ligands are comprised of molecules with an organic backbone interspersed with heteroatoms able to bind a variety of species. Macropolycyclic ligands are a 3-D extension of macrocyclic ligands, in which more than one macrocycle is incorporated into the same molecule. Multidentate macrocyclic and macropolycyclic ligands attract an increasing interest because they can function as receptors for several kinds of substrates, and because, after coordination, the physical and chemical properties of these substrates can be significantly modified. 

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