CROWN-ETHER DERIVATIVES OF CALIX[5] ARENES - SYNTHESIS AND COMPLEXATION PROPERTIES

Several crown ether derivatives of calix[5]- and tert-butylcalix[5]-ar ene have been synthesized arid converted into their trimethyl ethers a s neutral ligands, For selected examples extraction studies have been carried out with alkali metal picrates in the system water-dichloromet hane and stability constants have been determined by UV spectroscopy i n methanol, All ligands show a more or less pronounced preference for the larger alkali cations, The selectivity for Cs+ over Na+ is highest for the crown-5 derivative of tert-butylcalix[5]arene (5 = 630). Calo rimetric titrations show that the complexation is enthalpically and en tropically driven.