Synthesis and selective Cu(II) complexation of lower rim substituted thiacalixarenes containing pyrazole fragments

Selective sensors for the detection and quantification of Cu(II) ions are actively used to investigate in vivo conditions in Wilsons and Menkes diseases at the cellular level. Such sensors must have a high specificity for this cation as well as low toxicity. A synthetic approach for the preparation of selective sensors for Cu(II) cations based on p-tert-butylthiacalix[4]arenes modified with 3,5-dimethylpyrazole moieties in cone, partial cone and 1,3-alternate stereoisomeric forms was developed. The obtained compounds were characterized by single-crystal XRD, NMR and IR spectroscopy, MALDI MS, and elemental analysis. All synthesized thiacalixarene compounds formed complexes with Cu(II) with the binding constants in range logK = 4.44–4.63 and 1:1 stoichiometry. The structure of the obtained complexes was studied by NMR spectroscopy and DFT methods. The obtained results can be used to develop selective Cu(II) sensors.