A series of tributyl and triphenyltin benzoates, phenylacetates, and cinnamates, with different electron-withdrawing substituents, were evaluated for their selectivity as anion carriers and for their application in liquid-membrane potentiometric ion-selective electrodes. The tributyltin carboxylates exhibited good sensitivity and significant chloride selectivities, while the corresponding triphenyltin benzoates were much less active. The observed potentiometric response differences were related to Sn-atom Lewis acidity, as assessed by binding constants of chloride to the tin carriers determined from 117Sn-NMR titration experiments and theoretical simulations of the resulting titration curves. The thermodynamic characteristics as well as the expected chloride-carrier adducts in relation to starting substrates were analyzed theoretically by AM1 calculations.