Supramolecular Diversity in Bis(acylhydrazone) Crystals: Linker Effects, Polymorphism, and Gelator Assemblies

A series of previously unknown bis(acylhydrazone)s with aliphatic (zero to four CH2 units) and aromatic (phenylene substituted) linkers was synthesized and structurally characterized. Aliphatic derivatives exhibited distinct conformational geometries and packing motifs, with linker length critically affecting hydrogen bond interactions and energies. Aromatic derivatives revealed three polymorphs of the meta-substituted structure with two of the forms related by temperature. Additionally, a bis(acylhydrazone) low-molecular-weight gelator was crystallized, revealing a unique and impressive hydrogen-bonded framework with large water channels (952 Å3) and strong aliphatic and aromatic stacking interactions. These findings highlight the potential of bis(acylhydrazone)s in crystal engineering and supramolecular chemistry, especially in coformer design and selection, and supramolecular gelator applications.