Design, synthesis and structural characterisation of a bicompartimental bishydrazone ligand

In recent decades, hydrazone ligands have been extensively studied due to their versatility in coordination chemistry and because of their important biological properties (anticancer, antifungal, antimicrobial, etc.). These types of ligands are widely used in coordination chemistry, due to the variety of metallo-supramolecular architectures they can form. These include the formation of helicates, mesocates and clusters. Among the most relevant properties of metal complexes derived from hydrazone ligands are their interaction with biomolecules such as DNA, as well as their magnetic or antioxidant properties.

In this work, we present the design and synthesis of the bishydrazone ligand H₃L generated through an iminic condensation reaction between 2-hydroxyisophthalaldehyde and 2-hydroxybenzohydrazide. This synthesis is carried out using acid catalysis and ethanol as solvent. This ligand is bicompartimental, potentially pentadentate [N₂O₃] and trianionic. The presence of a spacer consisting of a phenolic group facilitates the coordination of transition and post-transition metal ions, resulting in a wide variety of metallo-supramolecular structures. Several characterisation techniques in solid state and in solution were used to confirm the formation and purity of the ligand, including elemental analysis, mass spectrometry, infrared spectroscopy and nuclear magnetic resonance. Moreover, it was also possible to analyse the structure of H₃L by X-ray diffraction studies.