Synthesis and Electrochemical Properties of Calix[4]arene-triester-monoquinones

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Abstract
Calix[4]arene-based monoquinones having three efficient ligating groups of alkoxycarbomethyl ethers were prepared and their ionophoric properties were investigated by electrochemical technique. Calix[4]-triester-monoquinones 3a and 3b were prepared from calix[4]arene and p-tert-butylcalix[4]arene by the selective trialkylation followed by oxidation with T1(NO3)3 and T1(CF3CO2)3, respectively. X-ray crystal structural analysis revealed that the ligand 3a adopted a partial cone conformation with an anti quinone moiety. MM+ calculations suggested that the energy difference between the two conformations is relatively small (< 3.5 kcal mole−1). Electrochemical studies also showed that the monoquinones 3a and 3b form strong complexes with Na+ ion, and the positive shifts in the reduction potential exceeded those of the closely related diquiones 5a and 5b.