Tetraureas versus Triureas in Sulfate Binding

By mimicking the scaffolds of oligopyridine-based ligands, triurea and tetraurea receptors have been developed for sulfate binding. The triureas (L-1, L-2) show stronger binding of sulfate than tetraureas (L-3, L-4) in DMSO because of their better conformational complementarity with sulfate, while the tetraureas display better water tolerance benefiting from the chelate effect and hydrophobic effect.