Intermolecular interactions of proton transfer compounds: synthesis, crystal structure and Hirshfeld surface analysis

Area of Science:

• Solid-state chemistry
• Crystallography
• Supramolecular chemistry

Background:

• Proton transfer compounds are fundamental in various chemical processes.
• Understanding crystal structures and intermolecular interactions is key to material properties.

Purpose of the Study:

• To synthesize and characterize novel proton transfer compounds.
• To elucidate the crystal structures and intermolecular interactions of these compounds using X-ray diffraction and Hirshfeld surface analysis.

Main Methods:

• Synthesis of three new proton transfer compounds: 2-ammonio-5-methylcarboxybenzene perchlorate, 4-(ammoniomethyl)carboxybenzene nitrate, and 4-(ammoniomethyl)carboxybenzene perchlorate.
• Single-crystal X-ray diffraction for crystal structure determination.
• Infrared (IR) spectroscopy for vibrational mode assignment.
• Three-dimensional Hirshfeld surface analysis and two-dimensional fingerprint maps to study intermolecular interactions.

Main Results:

• Successful synthesis and structural characterization of the three target compounds.
• Crystal structures reveal distinct asymmetric units for compounds 1, 2, and 3.
• Hirshfeld surface analysis indicates that H...O/O...H and H...H contacts are the dominant intermolecular interactions, accounting for approximately 70% of the surface area.
• O-H...O and N-H...O hydrogen bonds are the strongest interactions (~50%), followed by H...H contacts (~20%) and weak C...H/H...C contacts (~10%).

Conclusions:

• The synthesized compounds exhibit significant hydrogen bonding networks that dictate their crystal packing.
• Hirshfeld surface analysis provides valuable insights into the nature and contribution of various intermolecular forces in these proton transfer systems.
• The findings contribute to the understanding of structure-property relationships in organic salts.