Cation affinities of [1(6)]starand model. Comparison with 12-crown-4: Crucial role of dipolar moiety orientations
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- Title
- Cation affinities of [1(6)]starand model. Comparison with 12-crown-4: Crucial role of dipolar moiety orientations
- Authors
- Cui, CZ; Cho, SJ; Kim, KS
- Date Issued
- 1998-02-12
- Publisher
- AMER CHEMICAL SOC
- Abstract
- [1(6)]Starand appears to be a promising ionophore because of its rigid structure with the spherical cavity into which Li+ can fit perfectly. Using ab initio calculations, we investigated if the starand model has strong affinity as well as high selectivity for Li+, compared to 12-crown-4 of almost the same cavity size. Li+ favors the external binding (binding outside of the cavity) for the [1(6)]starand model. The ion-dipolar moiety interactions are found to be the main factors affecting the preference of external binding in the starand model. When a cation is located at the center of the starand model, the out-of-plane bending angle of a cation from the plane of the ketal moiety is more than 90 degrees, resulting in unfavorable energetics. By the same reasoning, the somewhat flexible 12-crown-4 structure, upon complexation with Li+ and Na+, drastically orients itself into a volcano structure with four oxygen atoms on the top so as to have favorable ion-dipolar moiety orientations with the cation located above the volcano. Therefore, in addition to the host-guest size complementarity, the ion-dipolar moiety orientations should be very important in designing novel ionophores.
- Keywords
- AB-INITIO; MOLECULAR-DYNAMICS; FREE-ENERGY; ION SELECTIVITY; ETHER COMPLEXES; CROWN-ETHERS; FORCE-FIELD; METAL-IONS; ALKALI; RECOGNITION
- URI
- https://oasis.postech.ac.kr/handle/2014.oak/20862
- DOI
- 10.1021/jp972591u
- ISSN
- 1089-5639
- Article Type
- Article
- Citation
- JOURNAL OF PHYSICAL CHEMISTRY A, vol. 102, no. 7, page. 1119 - 1123, 1998-02-12
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