,'-Dimethylsquaramide as a central scaffold for anionophore design.

The ,'-dimethylation of a diphenylsquaramide induces a conformational change in the orientation of the phenyl rings. This has been exploited to create a series of bis-urea, -thiourea and -squaramide anionophores. The compounds were shown to bind to Cl using proton NMR titration techniques and to transport H/Cl through the lipid bilayers, whereas a non-methylated analogue displayed limited transport activity. Despite their potency in transport studies, the series had a negligible impact on cancer cell viability.