Azocalixarenes. 4: synthesis, characterization and investigation of the absorption spectra of hetarylazo-substituted calix[6]arenes

Synthesis of seven novel hetarylazocalix[6] arene dyes was achieved by diazotisation of seven different heterocyclic amines using nitrosyl sulphuric acid, coupling with calix[6]arene. Hetarylazocalix[6]arene dyes were characterized based on FT-IR and 1H-NMR spectroscopic techniques as well as elemental analysis. The absorption spectra of the dyes are discussed, both the effect of varying pH and solvent upon the absorption ability of azocalixarenes. Absorption maxima of the prepared dyes showed large bathochromic effects in comparison with analogues dyes containing carbocyclic amine residue. The colour of the azocalixarene dyes is discussed with respect to the nature of the heterocyclic ring and substituents there in. Concentration effects on the visible absorption maxima of the dyes are also reported.