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+2in 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+2with the ligands. Also, L1 shows more attraction towards the smaller alkali and alkali earth metal ions than L2.

Keywords

• alkali and alkali earth cations
• calix[4]arene
• complexation
• formation constant
• synthesis