Complexation of di and tetra-benzyloxy ether derivatives of calix[4] arene with alkali metal cations

The synthesis and complexive abilities of 26, 28-bis-benzyloxy-25, 27-dihydroxy-5, 11, 17, 23-tetra-tert-butyl-calix[4] arene and 25, 26, 27, 28-tetra-benzyloxy-5, 11, 17, 23-tetra-tert-butyl-calix[4] arene towards alkali metal ions Li+, Na+, K+, Rb+, and Cs+ in methanol-chloroform mixture have been evaluated at 25 degrees C, using UV-Vis spectrophotometric techniques. The results showed that the ligands are capable to complex with all of the alkali cations by 1: 1 metal to ligand ratios. The selectivity presented considering the calculated stability constants are in the order Cs+ > Li+ > Rb+ > Na+ > K+ and Na+ congruent to Li+ congruent to Rb+ congruent to K+ > Cs+ for the first and second ligand, respectively.