Comparative study of novel sulfonylcalix[4]arene derivative compounds

Density functional theory (DFT) was applied to investigate the structure and conformational equilibrium of tetraaminosulfonylcalix[4]arene (1) and tetramercaptosulfonylcalix[4]arene (2) compounds, which are expected to contribute for the design of novel molecular receptors in supramolecular chemistry. All the calculations predict the 1,3-alternate as the most stable conformer for both compounds, which contrasts with an earlier theoretical study on the corresponding thiacalix[4]arene derivatives where cone was shown to be the most stable. The strong intramolecular hydrogen bonding between the substituent groups at the lower rim and the oxygen atoms of sulfone groups seem to play an important role in the stabilization of the conformers. Besides, the influence of the solvent chloroform was taken into account in this study. The results show that chloroform does not modify the stability ordering of the conformers, but leads to a reduction in the energy gaps between them. The presence of additional coordination sites provided by sulfone groups may induce new binding properties of the host molecule towards a variety of metal ions.