A comparison of the intramolecular and intermolecular hydrogen bonding of N,N'-ethylenebis(aminobenzylidene) in the solid state with its salen analogue

The crystal structure of H2amben has been elucidated for the first time. The close NHN contact between neighbouring molecules supports strongly the notion that intermolecular hydrogen bonding exists within the crystal lattice, creating a series of molecular chains, which are crosslinked in a three-dimensional array. This intermolecular bonding is suggested to account for the anomalously high melting point of H2amben (176-178 °C) compared to its H2salen counterpart (126-128 °C). Although strong intramolecular forces are present in both ligands, H2salen contains no intermolecular hydrogen bonds.