Transduction of selective recognition by preorganized lonophores; K+ selectivity of the different 1,3-diethoxycalix[4]arene crown ether conformers

Abstract

Three different conformers of 1,3-diethoxy-p-tert-butylcalix[4]arene crown ethers have been used to study the effect of the ionophore preorganization on the potentiometric K⁺-selectivity. Selectivities were measured for chemically modified field effect transistors (CHEMFETs) and membrane ion-selective electrodes (ISEs) by two different methods. The ionophores show decreasing K⁺/Na⁺ selectivities in the order: partial cone > 1.3-alternate > cone. As a function of time the cone conformer maintained a constant selectivity whereas a continuous decrease of the selectivity values was observed for the other two conformers. This supports our prediction based on the association constants and our previous ¹H NMR studies on conformational stability.