Complex formation of some tetraamido-type calix[4]arene derivatives detected by vibrational spectroscopy

Complex formation of five teraamido-type calix [4] arene derivatives-containing a heteroaromatic ring on the carboxamide moieties forming the coordination sphere-with alkali/alkali earth ions were the subject of FT-IR studies. The selectivity of these ligands toward different cations were found in acetonitrile solution, with the best detection in the case of the thiophene derivative, ligand 3, that exhibited selectivity to thallium(I) and thallium(III) ions over alkali/alkaline earth ions. Calixarenes 2 and 4 exhibit selectivity to potassium and ligand 5 to lithium ions among alkali/alkaline earth ions, however, thallium(I) ions show interference with these measurements. Moreover, selectivity was observed in solid state when surface complexes were prepared on sodium chloride, potassium chloride, bromide and iodide, calcium chloride and fluoride. The solid samples were examined by FT-Raman and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) method. Calixarenes 2 and 4 are of potential analytical application for the recognition of cations among alkali/alkaline earth metal ions in solid state by FT-IR spectroscopic detection. The number of methylene units in the substituents of calixarenes influences the efficiency of the complexation process significantly, as it can be seen from the comparison of ligands 1 and 2 both in solution and in the solid state. FT-Raman measurements on calcium chloride show that the attachment of the ligand molecules to the salt surface is accompanied by the squeezing of water molecules from some special positions of the hydrated salt lattice.