Probing cations recognized by a crown ether with the 3D-RISM theory. II. 18-crown-6 ether

• Main Authors: Y.Maruyama, M.Matsugami, Y.Ikuta
• Format: Article
• Language: English
• Published: Institute for Condensed Matter Physics 2007-09-01
• Series: Condensed Matter Physics
• Subjects: 3D-RISM theory; molecular recognition; crown ether; cation
• Online Access: http://dx.doi.org/10.5488/CMP.10.3.315
• ISSN: 1607-324X

In the previous study, we investigated the cation recognition by12-crown-4 ether with the 3D-RISM theory [Ikuta, Y. et al., Chem. Phys. Lett., 2007, 433, 403], and showed the applicability of the theory to the problem. The results show that a 12-crown-4 ether recognizes Li⁺ and Mg²⁺. 18-crown-6 ether is widely used in comparison with 12-crown-4ether. In this study, we calculated three-dimensional distributions of water as well as cations (Li⁺, K⁺, Mg²⁺, Ca²⁺) inside and outside 18-crown-6 ether in aqueous solutions of electrolytes. A 18-crown-6 ether recognizes not only Li⁺ and Mg²⁺ but also K⁺ and Ca²⁺. K⁺ is dehydrated in the host cavity whereas other cations are hydrated. It is found that a hydration structure, as well as cation size, is important for the molecular recognition by crown ether.