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

摘要

The complexation characteristics of tetramethyl (1) and tetraethyl esters (2) of p-tert-butylcalix[4]arene with alkali 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/6-31G method followed by B3LYP/6-31 G(d) single point calculation.B3LYP/6-31 G(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/mol better than that of potassium ion,respectively.The exo-complexation efficiencies of potassium ion to the cavity of 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/6-3 IG(d) calculation of the ethyl ester 2 shows 29.5 and 30.8 kcal/mol better exo-complexation efficiency for both sodium and potassium ions than the methyl ester 1.