COMPLEXATION OF ALKALI-METAL CATIONS BY CALIX[4]ARENE-BIS-CROWN-6 IN METHANOL, ACETONITRILE AND PROPYLENE CARBONATE

The interactions of Li+, Na+, K+, Rb+, and Cs+ with the ''double-crown calix,'' calix[4]arene-bis-crown-6, have been studied in methanol, ac etonitrile, and propylene carbonate at 25 degrees C using precise cond uctivity measurements. For Li+ and Na+ in solutions containing this ca lix[4]arene, only I:1 cation:ligand complexes are formed which permit the determination of the thermodynamic complexation formation constant s, K-f. The conductivity data strongly suggest that 2:1 cation-calixar ene complexes form with K+, Rb+, and Cs+. The existence of 2:1 complex es was experimentally confirmed for the potassium systems by a mass sp ectroscopic method.