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and Dong-Suk OhDepartment of Chemistry, Chung-Ang University, Seoul 156-756, KoreaReceived February 6, 2004The complexation characteristics of tetramethyl (1) and tetraethyl esters (2) of p-tert-butylcalix[4]arene withalkali metal cations have been investigated by ab initio calculation. The structures of endo- or exo-complexation of the hosts in cone conformation with alkali metal ions have been optimized using HF/6-31Gmethod followed by B3LYP/6-31G(d) single point calculation. B3LYP/6-31G(d) calculations suggest that exo-complexation efficiencies of sodium ion to the cavity of lower rim of hosts 1 and 2 are 27.1 and 25.8 kcal/molbetter than that of potassium ion, respectively. The exo-complexation efficiencies of potassium ion to the cavityof lower rim of hosts 1 and 2 are 33.3 and 31.5 kcal/mol better than the endo-complexation inside the upper rim(four aromatic rings) as expected from the experimental results. B3LYP/6-31G(d) calculation of the ethyl ester2 shows 29.5 and 30.8 kcal/mol better exo-complexation efficiency for both sodium and potassium ions thanthe methyl ester 1. Key Words : Calix[4]aryl ester, Complexation, Alkali metal ion, Ab initio calculation, B3LYP/6-31G(d)IntroductionRecently, there has been much progress in the computa-tional approaches in supramolecular chemistry, which maylead to the deeper microscopic insight into the structural andthermodynamical features involved in the processes ofmolecular recognition and supramolecular organization.

Ab Initio Study of Complexation of Alkali Metal Ions with Alkyl Esters of p-tert-Butylcalix[4]arene