Synthesis and Complexive Abilities in Cone Conformation of Lower Rim Functionalized Calix{4}Arene with Alkali Metal Cations

The synthesis and complexive abilities of 5,11,17,23-tetra-tert-butyl-28,26-di(bromopropoxy)-25,27-dihydroxycalix{4}arene (L1) and 5,11,17,23-tetra-tert-butyl-25,27-dibenzoxy-26,28-di(phenoxy)propoxycalix{4}arene (L2) towards alkali metal cations Li+, Na+, K+, Rb+ and Cs+ in methanol-chloroform mixture have been evaluated at 25 C, using UV-Vis spectrophotometric techniques. The results showed that the ligands are capable to complex with all the alkali cations by 1:1 metal to ligand ratios. Considering the formation constant values, the binding selectivities of the ligands towards alkali cations of the formed complexes are in the order Rb+ ≈K+ > Cs+ > Na+ > Li+ and Li+ > Na+ > K+ ≈ Rb+ ≈Cs+ for the ligands L1 and L2, respectively.