Complexation behaviour of p-t-butyl-calix[4]arene propoxy derivatives toward alkali metal cations in chloroform

Spectrophotometric technique is used to evaluate the alkali metal ion binding selectivity's of a series of calix[4]arenes in. chloroform solution. On the basis of formation constant values calculated, complexation of K+, Na+, and Li+ are favored toward di propoxy (L1), tri propoxy (L2), and bromopropoxy calix[4]arenes (L3), respectively, in agreement with the cavity sizes of the ligands. All ligands have been shown to form exclusively 1:1 (metal ion to ligand ratio) complexes with alkali cations in our experimental conditions. Chloroform stabilize endo complexes and the spectrophotometery results predict that in weakly polar solvents endo complexation is preferred.