Ab initio investigation of the structure and alkali metal cation selectivity of 18-crown-6

Journal Article · Wed Nov 16 00:00:00 EST 1994 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00102a035· OSTI ID:7079581

Glendening, E D; Feller, D; Thompson, M A ^[1]

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

We present an ab inito, quantum mechanical study of 18-crown-6 (18c6) and its interaction with the alkali metal cations Li[sup +], Na[sup +], K[sup +], Rb[sup +], and Cs[sup +]. Geometries, binding energies, and binding enthalpies are evaluated at the restricted Hartree-Fock (RHF) level using standard basis sets (3-21G and 6-31 + G*) and relativistic effective core potentials. Electron correlation effects are determined at the MP2 level, and wave function analysis is performed by the natural bond orbital (NBO) and associated methods. The affinity of 18c6 for the alkali metal cations is quite strong (50-100 kcal mol[sup [minus]1], depending on cation type), arising largely from the electrostatic (ionic) interaction of the cation with the nucleophilic ether backbone. Charge transfer (covalent bonding) contributions are somewhat less important, only 20-50% as strong as the electrostatic interaction. Agreement of the calculated binding enthalpies and experimentally determined quantities is rather poor. For example, the binding energy for K[sup +]/18c6 (-71.5 kcal mol[sup [minus]1]) is about 30 kcal mol[sup [minus]1] stronger than that determined by experiment, and it is not clear how to reconcile this difference. Our calculations clearly show that solvation effects strongly influence cation selectivity. 48 refs., 12 figs., 5 tabs.

• DOE Contract Number: AC06-76RL01830; FG06-89ER75522
• OSTI ID: 7079581
• Journal Information: Journal of the American Chemical Society; (United States), Vol. 116:23; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
ALKALI METAL COMPOUNDS
CHEMICAL REACTIONS
HYDRATION
SOLVATION
CROWN ETHERS
ELECTRONIC STRUCTURE
MOLECULAR STRUCTURE
CHARGE TRANSPORT
CHEMICAL BONDS
ENTHALPY
HARTREE-FOCK METHOD
MOLECULAR ORBITAL METHOD
QUANTUM MECHANICS
WAVE FUNCTIONS
CALCULATION METHODS
ETHERS
FUNCTIONS
MECHANICS
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
THERMODYNAMIC PROPERTIES
400201* - Chemical & Physicochemical Properties
990200 - Mathematics & Computers