| Summary: | A series of syringaldehyde imines with <i>para</i>-substituted anilines have been synthesized in a good yield, and their crystal structures have been analyzed. The orientation of the syringaldehyde hydroxyl group plays in important role in the intermolecular hydrogen-bonding pattern of the molecules. The O–H<sup>…</sup>N hydrogen bonding interactions primarily determine the three-dimensional packing of the molecules, even though they make up a relatively small percentage of intermolecular interactions in the molecules. The three structures with the p-hydroxy group <i>cis</i> to the imine group give hydrogen-bonded zigzag chains in the monoclinic crystals, while the structure with a <i>trans</i> hydroxy group crystallize in a hexagonal space group (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>R</mi><mover accent="true"><mn>3</mn><mo>¯</mo></mover></mrow></semantics></math></inline-formula>) and form hydrogen-bonded hexamers. The hexagonal structure also displays Br<sup>…</sup>Br interactions, forming additional hexameric clusters. The analysis of published <i>p</i>-hydroxyphenyl imine crystal structures from the Cambridge Crystallographic Database revealed patterns in the length of the hydrogen bonding interactions based on steric congestion around the hydroxyl group.
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