Chelating chloride using binuclear lanthanide complexes in water.

Halide recognition by supramolecular receptors and coordination complexes in water is a long-standing challenge. In this work, we report chloride binding in water and in competing media by pre-organised binuclear kinetically inert lanthanide complexes, bridged by flexible -(CH)- and -(CH)- spacers, forming [Ln(DO3A)C-2] and [Ln(DO3A)C-3], respectively. These hydrophilic, neutral lanthanide coordination complexes are shown to bind chloride with apparent association constants of up to 10 M in water and in buffered systems.