High Complexation Ability of Thiacalixarene with Transition Metal Ions. the Effects of Replacing Methylene Bridges of Tetra(p-t-butyl)calix[4]arenetetrol by Epithio Groups

The ability of tetra(p-t-butyl)tetrathiacalix[4]arenetetrol (TCA, H₄L), a cyclic tetramer of p-(t-butyl)phenol bridged with four epithio groups, to bind metal ions was investigated via a solvent extraction study. Although tetra(p-t-butyl)calix[4]arenetetrol (CA) has very poor affinity for transition metal ions (M²⁺), TCA is an excellent extradant of these metal ions. The chemical formulae of the extracted TCA metal complexes were found by slope analysis to be neutral 1:1 complexes [MH₂L]. The origin of the high affinity of TCA for transition metal ions is discussed, in which it is suggested that ligation of the epithio group is important as evidenced by an NMR study of the [ZnH₂L] complex.