International audienceThe complexing properties of a thiacalix[2]thianthrene 1 and its disulfoxide derivative 2 toward alkali metal, alkaline earth metal, some transition metal and some heavy metal cations have been investigated in acetonitrile by means of UV spectrophotometry. At the concentrations suited to this technique, complexation of the alkali metal cations by the sulfoxide but not the thiacalixthianthrene was detectable, whereas the converse was true for both transition metal and lanthanide cations. Complexation of the alkaline earth cations was not detectable. The strongest binding observed was that of Hg(II) to ligand 1 but in no case was complexation sufficiently strong for either ligand to function as a useful metal ion extractant. Graphical Abstract The complexing properties of a thiacalix[2]thianthrene 1 and its disulfoxide derivative 2 toward alkali metal, alkaline earth metal, some transition metal and some heavy metal cations have been investigated in acetonitrile by means of UV spectrophotometry. At the concentrations suited to this technique, complexation of the alkali metal cations by the sulfoxide but not the thiacalixthianthrene was detectable, whereas the converse was true for both transition metal and lanthanide cations. Complexation of the alkaline earth cations was not detectable. The strongest binding observed was that of Hg(II) to ligand 1 but in no case was complexation sufficiently strong for either ligand to function as a useful metal ion extractant