Copper(II)-induced gel formation of a carboxylate functionalized calix[4]arene and its application for sensing of iodide

Carboxylate functionalized calix[4]arene derivatives with ter-butyl groups at the upper rim exhibits gel formation in presence of Cu(ClO₄)_2, DMF, methanol and water with specific ratio (5:3:2). In presence of other metal ions or with different combination of solvents gel formation didn’t occur. The morphology of the gel has been investigated by SEM and TEM study. Detail study revealed that gel formation takes place when network structure is formed immobilizing the solvent(s) molecule in the cavity through nonbonding interaction. This gel material functions as a colorimetric sensing agent for iodide. The binding constant for iodide and LOD was also determined.