An octahedral template based on a new molecular turn: Synthesis and structure of a model complex and a reactive, diphenolic ligand and its metal complexes

The design and synthesis of a new family of tridentate Schiff base ligands for use in octahedral molecular templates has been successfully demonstrate d. As anticipated, two molecules of the ligand, 2,6-pyridinedicarboxaldhyde bis-(p-hydroxyphenylimine), coordinate equatorially to six-coordinate octah edral metal ions to give orthogonally oriented molecular turns around the a nchoring metal ion. This new template offers the advantages that (1) synthe ses of the Ligand and its complexes are straightforward, giving high yields in simple, one-pot reactions, and (2) structural variations are easily acc omplished. X-ray structural analysis has shown that the ligand will only fu nction as a turn when its spatial organization is controlled by coordinatio n to a metal ion. Upon chelation, the phenolic groups are directed across a nd beyond the metal ion center, and, unlike earlier ligands of this general type which lacked reactive moieties, substitution reactions may be carried out at the free phenolic groups of the octahedral complex. These reactions remain to be optimized in order to achieve the long-term goal of proving t heir value as synthons for interlocked molecules.