Highly potent but structurally simple transmembrane anion transporters are reported that function at receptor to lipid ratios as low as 1 : 1 000 000. The compounds, based on the simple ortho-phenylenediamine-based bisurea scaffold, have been studied for their ability to facilitate chloride/nitrate and chloride/bicarbonate antiport, and HCl symport processes using a combination of ion selective electrode and fluorescence techniques. In addition, the transmembrane transport of dicarboxylate anions (maleate and fumarate) by the compounds was examined. Molecular dynamics simulations showed that these compounds permeate the membrane more easily than other promising receptors corroborating the experimental efflux data. Moreover, cell based assays revealed that the majority of the compounds showed cytotoxicity in cancer cells, which may be linked to their ability to function as ion transporters.