Synthesis of new calix[4]arenequinone as alkali metal sensor

Abstract

25,27-Di(ethyleneglycol)-bis-p-tert-butylcalix[4]arene 1, 25,27-di(diethyleneglycol)-bis-p-tert-butylcalix[4]arene 2b and 25,27-di(methoxy)-26,28-di(ethyleneglycol)-bis-p-tert-butylcalix[4]arene 4d were synthesized. Quinone derivatives 25,27-di(ethyleneglycol)-bis-p-tert-butylcalix[4]tetraquinone 5a, 25,27-di(diethylene-glycol)-bis-p-tert-butylcalix[4]tetraquinone 5b and 25,27-di(methoxy)-26,28-di(ethylene-glycol)-bis-p-tert-butylcalix[4]diquinone 5c were obtained from reactions of 1, 2b and 4d, respectively with Tl(CF[subscript 3]COO)[subscript 3] in CF[subscript 3]COOH. Complexation studies of ligands 5a, 5b and 5c with alkali metals such as Li[superscript +], Na[superscript +], K[superscript +] and Cs[superscript +] were carried out by 1H-NMR titrations. Ligands 5a and 5c were able to form 1:1 complexes with Li[superscript +], Na[superscript +] and K[superscript +] and binding abilities were as follows; Na[superscript +] > Li[superscript +] >> K[superscript +] and Na[superscript +] >> Li[superscript +] > K[superscript +]. Ligand 5b was able to form 1:1 complexes with Li[superscript +], Na[superscript +], K[superscript +] and Cs[superscript +]. Because of its bigger cavity compared to 5a and 5c, 5b showed selectivity for Cs[superscript +]. The binding trend for 5b was Cs[superscript +] > K[superscript +] > Na[superscript +] >> Li[superscript +]. Electrochemical studies using cyclic voltammetry and square wave voltammetry showed significant changing of voltammograms of 5a, 5b and 5c upon addition of alkali cations. Shifts of voltammograms signified the effect of hard-soft acid of alkali cations upon changing of electrochemical properties of the 3 ligands.