Abstract

Facilitated ion transfer (FIT) occurs when transport of an ion between two phases is enhanced by complexation with a receptor molecule. FIT is applied in technologies including ion sensing and removal of harmful ions from waste.¹ Here, electrochemistry at the interface between two immiscible electrolyte solutions (ITIES) was used to study FIT. FIT of K⁺ by dibenzo-18-crown-6 (DB18C6)^2,5 and FIT of Tb³⁺ by a tripodal carbamoylmethylphosphine oxide ligand (TREN-CMPO-OEt) were characterized using cyclic voltammetry at water/1,2-dichloroethane (DCE) micro-interfaces. The Tomeš criterion measured in steady state voltammograms were 75.4 mV and 45.2 mV for the K⁺–DB18C6 and Tb³⁺–TREN-CMPO-OEt transfers, respectively, consistent with reversible or quasi-reversible binding of the two ions. The binding constant for the K⁺–DB18C6 complex in DCE was measured to be 1.6 × 10¹⁰. Future work will include screening of organic ligands for their ability to bind Tb³⁺ and investigation of unassisted Tb³⁺ transfer.