Systematic studies on benzimidazole derivatives: Molecular structures and their hydrogen bond networks formation toward proton transfer efficiency

► A series of benzimidazole derivatives, i.e., mono-, di-, and trifunctional benzimidazole-based derivatives are prepared as a model compound to investigate (i) how benzimidazoles develop the hydrogen bond patterns and their consequent packing structure and (ii) how hydrogen bond as well as the packing structure plays the role in proton transferring. ► The number of benzimidazole functional group in a single molecule initiates different packing structures under hydrogen bond network of which the monofunctional benzimidazole (B-1) provides a perpendicular hydrogen bond network whereas the difunctional benzimidazoles (B-2 and B-3) provide a parallel hydrogen bond network under lamellar structure while the trifunctional benzimidazole (B-4) forms a helical hydrogen bond network under columnar structure. ► The favourable packing structure with strong H-bond formation leads to an effective proton transfer of B-4 as observed the highest proton conductivity of B-4 as high as 7.8 × 10−2 S cm−1 at 170 °C.