On the relative stabilities of the alkali cations 222 cryptates in the gas phase and in water-methanol solution.
J Mol Model
; 13(9): 1017-25, 2007 Sep.
Article
em En
| MEDLINE
| ID: mdl-17632741
The relative stabilities of the alkali [M subset 222]+ cryptates (M = Na, K, Rb and Cs) in the gas phase and in solution (80:20 v/v methanol:water mixture) at 298 K, are computed using a combination of ab initio quantum-chemical calculations (HF/6-31G and MP2/6-31+G*//HF/6-31+G*) and explicit-solvent Monte Carlo free-energy simulations. The results suggest that the relative stabilities of the cryptates in solution are due to a combination of steric effects (compression of large ions within the cryptand cavity), electronic effects (delocalization of the ionic charge onto the cryptand atoms) and solvent effects (dominantly the ionic dessolvation penalty). Thus, the relative stabilities in solution cannot be rationalized solely on the basis of a simple match or mismatch between the ionic radius and the cryptand cavity size as has been suggested previously. For example, although the [K subset 222]+ cryptate is found to be the most stable in solution, in agreement with experimental data, it is the [Na subset 222]+ cryptate that is the most stable in the gas phase. The present results provide further support to the notion that the solvent in which supramolecules are dissolved plays a key role in modulating molecular recognition processes.
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01-internacional
Base de dados:
MEDLINE
Assunto principal:
Éteres de Coroa
/
Álcalis
Tipo de estudo:
Health_economic_evaluation
Idioma:
En
Revista:
J Mol Model
Assunto da revista:
BIOLOGIA MOLECULAR
Ano de publicação:
2007
Tipo de documento:
Article
País de afiliação:
Brasil
País de publicação:
Alemanha