Synthesis and cation binding properties of new arylazo- and heteroarylazotetrathiacalix[4]arenes

New macrocyclic tetrathiacalix[4]arenes have been synthesized by incorporating arylazo-, thiazoleazo- and β-naphthylazo- units in the tetrathiacalix[4]arene molecular architecture through diazotization and coupling reactions. The new compounds have been characterized by 1H NMR, 13C NMR and FAB-MS spectroscopic analysis. X-ray crystallography for one of the new dyes () reveals that the compound is present in the cone conformation. The synthesized macrocycles have been examined for their binding with alkali (Li+, Na+, K+, Cs+ and Rb+), alkaline earth (Ca2+, Mg2+ and Ba2+) and transition metal cations (Cr3+, Fe2+, Co2+, Ni2+, Cu2+, Hg+, Hg2+, Pd2+ and Pt2+) by UV–visible spectroscopy to reveal selective bathochromic shifts for heavier alkali metal ions (cesium and rubidium) and palladium in a 1:1 and 2:1 stoichiometry respectively. The study has a significant bearing on the development of useful ionic filters and sensor materials.