Influence of supramolecular structures in crystals on parallel stacking interactions between pyridine molecules

Area of Science:

• Crystal Engineering
• Supramolecular Chemistry
• Organic Solid-State Chemistry

Background:

• Pyridine stacking interactions are crucial in crystal engineering.
• Understanding these interactions requires analyzing their geometries and influencing factors.
• Hydrogen bonding and supramolecular structures significantly impact molecular arrangements in crystals.

Purpose of the Study:

• To investigate parallel stacking interactions of pyridines in crystal structures.
• To analyze the influence of hydrogen bonding and supramolecular structures on pyridine interaction geometries.
• To compare experimental crystal data with theoretical calculations.

Main Methods:

• Analysis of crystal structure data from the Cambridge Structural Database (CSD).
• Identification and quantification of parallel pyridine contacts.
• Comparison of observed geometries with computationally derived values.

Main Results:

• 66 parallel pyridine contacts were identified in the CSD, with 44 involving hydrogen bonds.
• The mean perpendicular distance (R) between stacked pyridine rings was larger in crystal structures than calculated, influenced by supramolecular effects.
• Pyridine stacks with hydrogen bonds exhibited preferred offsets (1.25-1.75 Å), aligning with calculated minima, while those without showed deviations.

Conclusions:

• Hydrogen bonding and supramolecular structures significantly influence the geometries of parallel pyridine stacking in crystals.
• Weaker stacking interactions in pyridines without hydrogen bonds are more susceptible to supramolecular influences.
• Observed deviations from calculated geometries highlight the importance of crystal packing in determining interaction characteristics.