3D energy frameworks of dimethylbenzophenone tetramorphs

Area of Science:

• Solid-state chemistry
• Crystallography
• Materials science

Background:

• Polymorphism, the ability of a solid material to exist in multiple crystal forms, significantly impacts material properties.
• Understanding crystal packing and intermolecular interactions is crucial for controlling solid-state behavior.
• 4,4-dimethylbenzophenone is a compound known to exhibit polymorphism.

Purpose of the Study:

• To synthesize and characterize a new crystalline form (tetramorph D) of 4,4-dimethylbenzophenone.
• To elucidate the crystal structure and packing of tetramorph D using single crystal X-ray diffraction.
• To comparatively analyze the structural features, intermolecular interactions, and energy frameworks of the four known tetramorphs (A, B, C, and D).

Main Methods:

• Slow-evaporation crystallization method for obtaining single crystals of 4,4-dimethylbenzophenone polymorph D.
• Single crystal X-ray diffraction for precise determination of unit cell parameters and molecular structure.
• Analysis of crystal packing using Hirshfeld surfaces, enrichment ratios, energy frameworks, and 3D-topology.

Main Results:

• Tetramorph D of 4,4-dimethylbenzophenone was successfully crystallized in the orthorhombic system (space group Pbca).
• Intermolecular C−H···π interactions were identified as key stabilizers for the crystal packing of tetramorph D.
• Conformational differences and varying contributions of H···H and C···H contacts were observed across the four tetramorphs, with dispersion energy dominating over electrostatic energy in crystal packing.

Conclusions:

• The discovery of tetramorph D adds to the known polymorphic forms of 4,4-dimethylbenzophenone, specifically as the second orthorhombic candidate.
• Systematic comparison reveals distinct molecular packings and stabilization mechanisms among the tetramorphs.
• The study highlights the importance of intermolecular interactions and energy frameworks in understanding and differentiating polymorphic structures.