Grinding-induced equimolar complex formation between thiourea and ethenzamide

Area of Science:

• Solid-state chemistry
• Crystallography
• Materials science

Background:

• Thiourea and ethenzamide are organic compounds with potential for co-crystal formation.
• Grinding is a mechanochemical method for inducing solid-state reactions and forming new crystalline phases.
• Understanding co-crystal formation is crucial for modifying material properties.

Purpose of the Study:

• To investigate the formation of a grinding-induced equimolar complex between thiourea and ethenzamide.
• To determine the optimal conditions and stoichiometry for complex formation.
• To elucidate the structural and chemical factors governing the complexation.

Main Methods:

• Co-grinding of thiourea and ethenzamide at various molar ratios.
• Powder X-ray Diffraction (PXRD) for phase analysis.
• Differential Scanning Calorimetry (DSC) for thermal analysis.
• Fourier Transform Infrared Spectroscopy (FTIR) for chemical interaction analysis.
• Single-crystal X-ray diffraction for structural determination.

Main Results:

• A new equimolar (1:1 mol/mol) complex of thiourea-ethenzamide was successfully prepared via grinding.
• PXRD confirmed the formation of a new crystalline phase distinct from the starting materials.
• Intermolecular hydrogen bonding between thiourea and ethenzamide was identified as the driving force for complex formation.
• Complex formation was specific to 2-alkoxy benzamide derivatives, not observed with benzamide, salicylamide, or 3-ethoxybenzamide.

Conclusions:

• Grinding is an effective method for preparing thiourea-ethenzamide equimolar complexes.
• The crystal structure of the complex is stabilized by specific intermolecular hydrogen bonds.
• The presence of a 2-alkoxy group on the benzamide moiety is essential for this grinding-induced complexation with thiourea.