Ab initio investigation of the structure and alkaline earth divalent cation selectivity of 18-crown-6

Journal Article · Wed Jun 26 00:00:00 EDT 1996 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/ja960469n· OSTI ID:282998

Glendening, E D; Feller, D ^[1]

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1. Pacific Northwest National Lab., Richland, WA (United States)

We present an ab initio, quantum mechanical study of 18-crown-6 (18c6) and its interaction with the alkaline earth dications Mg{sup 2+}, Ca{sup 2+}, Sr{sup 2+}, Ba{sup 2+}, and Ru{sup 2+}. Geometries, binding energies, and binding enthalpies are evaluated at the restricted Hartree-Fock (RHK) and second-order Moller-Plesset perturbation (MP2) levels of theory using the 6-31+G{sup *} basis set and relativistic effective core potentials. The affinity of 18c6 for the dications is considerable, ranging from 150-300 kcal mol{sup -1}. The cation-18c6 interaction arises principally from the electrostatic interaction of the dication with the nucleophilic ether backbone and from the polarization of the crown ether by the electric field of the dication. Whereas Ba{sup 2+} selectivity is observed for 18c6 in aqueous environments, our calculations clearly show that the crown ether in fact binds Mg{sup 2+} most strongly in gas phase. Thus, solvation effects appear to strongly influence cation selectivity. Indeed, Ba{sup 2+} selectivity is recovered when we consider the competition of the solvent and 18c6 molecules for the dications using a simple cation exchange reaction. 61 refs., 7 figs., 3 tabs.

• DOE Contract Number: AC06-76RL01830; FG06-89ER75522
• OSTI ID: 282998
• Journal Information: Journal of the American Chemical Society, Vol. 118, Issue 25; Other Information: PBD: 26 Jun 1996
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
66 PHYSICS
99 MATHEMATICS
COMPUTERS
INFORMATION SCIENCE
MANAGEMENT
LAW
MISCELLANEOUS
CROWN ETHERS
STRUCTURAL CHEMICAL ANALYSIS
BINDING ENERGY
QUANTUM MECHANICS
MAGNESIUM IONS
CALCIUM IONS
STRONTIUM IONS
BARIUM IONS
RUTHENIUM IONS
MOLECULAR MODELS
ENTHALPY
HARTREE-FOCK METHOD
SOLVATION
CALCULATION METHODS