ISSN:
1573-1111
Keywords:
Cesium cryptate stabilities
;
high dielectric solvents
;
133Cs NMR
;
electrostatic nature of complexation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The chemical shift of the133Cs resonance has been measured as a function of the mole ratio of cryptands C222, C222B, C221, and C211 to the Cs+ ion inN-methylformamide and dimethylacetamide solutions. The overall formation constants of the cesium cryptates were calculated from the NMR titration curves. From these and previously reported data it is clear that solvent properties such as dipole moment, donicity, dielectric constant and hydrogen bonding ability affect macrocyclic ligand-cation complexation equilibria through specific solvation of the cation, the ligand and the complex. A model of M+ · L bonding in solution, involving a rather intimate electrostatic attraction between the cation and the local electron distribution of the macrocycle accompanied by little perturbation of the charge distributions of the separated partners, is presented. In addition to the specific interactions previously noted, the presence of the solvent mitigates the ion-multipole forces which would otherwise govern the long-range attraction.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01053866
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