Thiourea–isothiouronium conjugate for strong and selective binding of very hydrophilic H2PO4− anion at the 1,2-dichloroethane–water interface

Potential use of a surfactant-like receptor is demonstrated at the 1,2-dichloroethane–water interface for strong and selective binding of H2PO4− over Br− and Cl−. The analysis by interfacial tensiometry reveals that the interfacial adsorption of a thiourea–isothiouronium conjugate, BT-C1, is significantly stabilized by the binding of H2PO4− with the adsorption constant of 1.7 × 105 M−1 while the interfacial adsorptivity of this receptor is relatively moderate for Br− (0.81 × 105 M−1) and Cl− (0.63 × 105 M−1). Such complexation-induced interfacial adsorption behaviors of BT-C1 are discussed as a basis for the development of receptor-based chemical sensors for phosphate anions.