Synthesis and complexive abilities in cone conformation of upper rim functionalized of calix[4]arene with alkali and alkali earth cations

Abstract The synthesis and complexive abilities of 5-mono­[(tert-butoxycarbonyl)-amino]-11,17,23-triamino-25,26,27,28-tetrabutoxycalix[4]arene (L1) and 5,11,17,23-tetrakis[(tert-butoxycarbonyl)-amino]-25,26,27,28-tetrabutoxycalix[4]arene (L2) towards the alkali cations Li + , Na + , K + , Rb + , Cs + and the alkali earth cations Mg +2 , Ca +2 , Sr +2 and Ba +2 in methanol-chloroform mixture have been evaluated at 25°C using UV-Vis spectrophotometric techniques. The results show that the ligands are capable of complexing with all the cations by 1:1 metal to ligand ratios. Molecular mechanics calculations have been used to model the geometries of the alkali and alkali earth cations with the ligands using the Hyperchem 7 computational package. The selectivity is presented considering that the calculated formation constants are in the order Li + >>Na + >K + >Rb + >Cs + and Mg +2 >Ca +2 >Sr +2 >Ba +2 with the ligands. Also, L1 shows more attraction towards the smaller alkali and alkali earth metal ions than L2.