Synthesis and Characterization of 5- and 7-Donor Schiff Base Ligands and Spectroscopic Evidence for Tautomerism: A Crystal Structure Showing Tautomeric Forms Within One Ligand

An improved method for the synthesis of fifteen Schiff base ligands, of which six are novel, are reported. Optimised yields were obtained and the ligands have been fully characterized via several analytical techniques. It was found that tautomeric forms of these novel ligands exist and spectroscopic evidence for this phenomenon is provided. A crystal structure illustrating both enol and keto tautomeric forms in a new ligand, complements spectroscopic evidence obtained. To our knowledge, this is the first reported evidence of tautomeric forms within the same ligand.