Macropolycyclic ligands dimensionality

Macropolycyclic ligands, 2,942 classification, 2,917 metal complexes binding sites, 2, 922 cavity size, 2,924 chirality, 2, 924 conformation, 2,923 dimensionality, 2, 924 electronic effects, 2, 922 shaping groups, 2,923 structural effects, 2,922 molecular cation complexes, 2,947 molecular neutral complexes, 2,952 multidentate, 2,915-953 nomenclature, 2,920 Macro tetrolide actins metal complexes, 2,973 Macrotricycles anionic complexes, 2,951 cylindrical... 

Macropolycyclic ligands containing intramolecular cavities of a three-dimensional nature are referred to as cryptands. The bicyclic cryptands (73) exist in three conformations with respect to the terminal nitrogen atoms, exo-exo, endo-exo and endo-endo 6 these forms can rapidly interconvert via nitrogen inversion but only the endo-endo form has been found in the crystal structures of a variety of complexes372 and for the free ligand ([2.2.2], 73, m = n = / = l).449 In their complexes with alkali and alkaline earth cations, the cryptands exhibit an enhanced stability over the crown ethers and coronands dufe to the macrobicyclic, or cryptate, effect.33 202... 

Because the definition of metal ion encapsulation or its absence is, to a certain extent, ambiguous, we first describe the conventional criteria that we use to restrict the scope of the compounds to be considered. The major signs of complexation (formation of a complex) with an encapsulated metal ion are (a) a three-dimensional cavity (capsule, cage) produced by a macropolycyclic ligand and (b) metal ion coordinating heteroatoms in this cavity that isolate this metal ion from the environment. 

Macropolycyclic ligands, commonly referred to as cryptands, contain intramolecular cavities of three-dimensional shape ( crypts"). In their complexes Q cryptates") with alkali and alkaline earth cations, they display considerably enhanced stabilities with respect to crown ethers " cryptate effect") Thus, the K complex of... 

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