Initial mechanistic investigations into electrogenic F -transport were also performed due to the better size match with the tetralactam cavity for F -compared to Cl -. Due to the free diffusion of HF through the lipid bilayer when vesicles are treated with Mon, electroneutral H + /F -co-transport could not be investigated. The experiments required slight alterations to the conditions used in the regular cationophore coupled transport assay, which has been previously reported by our group. An internal solution of KF was used instead of KCl, and a fluoride ISE was used. Generally, the phenylene-linked transporters facilitated low to moderate levels of electrogenic F -uniport in the presence of Vln. Notably, the F-substituted naphthalene-linked transporter (2c) achieved the highest electrogenic F -efflux of 57%; however, the other naphthalene-linked tetralactams performed very poorly. The 4,5-difluorophenylene-linked transporters also facilitated low to moderate levels of F -efflux when tested with both Vln-treated and untreated vesicles, suggesting the ability to elicit unaided F -transport and possibly very efficient H + /F -cotransport. Due to solubility and inactivity, each tetralactam was tested at different concentrations, preventing further comparisons by kini rates or EC50 values.