Recognition of Anions Using p-Nitrophenyl Thiourea Based on 1,1'- Binaphthyl-2,2'-diol

The di-thioureas (1) and mono-thioureas (3) based on 1,1'-binaphthyl-2,2'-diol exhibited a preference for Cl- with a 1:1 stoichiometry. The cooperativity of the two binding sites (two thiourea groups for 1, thiourea and hydroxyl groups for 3) for anion binding was established by comparing the binding of the mono-thiourea receptors (2) based on naphthyl.