Syntheses and Crystal Structures of New “Extended” Building Blocks for Crystal Engineering:  (Pyridylmethylene)aminoacetophenone Oxime Ligands

Abstract

The syntheses and crystal structures of four new ligands based on “extended” (pyridylmethylene)aminoacetophenone oxime derivatives are reported. The ligands are all prepared in good yields by allowing a suitably substituted pyridine to react with hydroxylamine, followed by Schiff-base condensation with the appropriate pyridinecarboxaldehyde. Their solid-state structures show that the dominating hydrogen bond, a head-to-tail O−H···N interaction between the oxime O−H moiety and the pyridine nitrogen atom, is present in each of the four reported cases despite considerable differences in crystal packing. These structures also contain a multitude of weaker π−π interactions, but they do not display the same consistency and regularity as the O−H···N hydrogen bond, which illustrates the importance of hydrogen bonding as the primary supramolecular synthetic tool.