Macrobicyclic effect

Mach-Zehnder interferometer, 22 153 Mackenzie-Shuttleworth model, 23 75 Mackie line effect, 19 209, 210 Macor glass-ceramic, 22 635 Macquartite, 6 471t Macrinite, 6 707t Macrobicyclic effect, 24 39 Macrocrystalline wax, 26 214 Macrocycles, 24 35, 45 developments of, 24 36 Macrocyclic complexes, rhodium, 29 645 Macrocyclic compounds, chelating agents, 5 710, 713t... 

K. 4.38 Dietrich et al., 1973 Lehn and Simon, 1977). This macrobicyclic effect has been shown to be of enthalpic origin (Kaufmann et al., 1976 Anderegg, 1975). 

The aim of introducing additional binding sites at strategic positions near the cavity of the crown ether is to create a three-dimensional array of binding sites without calling in the help of the macrobicyclic effect. Gramain and Frere (1979) have studied the effect of two additional OH sites on the complexing... 

Figure 23 The macrocyclic and macrobicyclic effects (A) on complex stability the values given are the stability constants iog Ks of the K+ complex in methanol (top) and methanol/water (95.5) (bottom) (reproduced with...

Metal complexes with podands are usually less stable and more labile than the corresponding coronates and cryptates. This is also true for rare earth ions, although the macrocyclic and macrobicyclic effects tend to be smaller than those observed for M(I) and M(II) ions, which have a smaller cationic charge. Some rare earth podates and complexes with naturally occurring ionophores are listed in table 6. 

Macrocyclic ligands and their open-chain analogues have added a new dimension to the coordination chemistry of lanthanide ions. In particular, they allowed the study of high and unusual coordination numbers, e.g. 11-coordination. Basic thermodynamic data are still needed to get a better understanding of the complexation process and of both macrocyclic and macrobicyclic effects. Moreover, kinetic data on ligand exchange remain scarce and studies in this field are certainly desirable. 

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