Methylthioureas and their morpholine and dioxane adducts; hydrogen-bonding patterns

Area of Science:

• Crystallography
• Solid-state chemistry
• Molecular structure

Background:

• Thioureas are versatile organic compounds with applications in various chemical fields.
• Understanding the crystal structures of thioureas and their adducts is crucial for predicting their physical and chemical properties.
• Previous structural data for some substituted thioureas may require refinement or further investigation.

Purpose of the Study:

• To redetermine the crystal structures of methylthiourea (MTU) and 1,1-dimethylthiourea (1,1-DMTU).
• To investigate the crystal structure of 1,3-dimethylthiourea (1,3-DMTU).
• To determine the structures of crystalline adducts of MTU and dimethylthioureas with morpholine and 1,4-dioxane, and the structure of tetramethylthiourea (TetMTU).

Main Methods:

• Single-crystal X-ray diffraction was employed to determine the molecular and crystal structures.
• Analysis of intermolecular interactions, including hydrogen bonding (N-H...S=C, C-H...S) and van der Waals forces.
• Examination of molecular conformations and packing arrangements in the solid state.

Main Results:

• The structures of MTU and 1,1-DMTU were redetermined, showing specific molecular conformations and hydrogen bonding patterns.
• The crystal structure of 1,3-DMTU was investigated but found to be severely disordered.
• Novel crystalline adducts of MTU and dimethylthioureas with morpholine and 1,4-dioxane were characterized, revealing diverse packing motifs, including dimers and chains.
• The structure of tetramethylthiourea (TetMTU) was determined, exhibiting crystallographic symmetry and distortions due to steric effects.

Conclusions:

• The study provides detailed structural insights into a series of thiourea derivatives and their adducts.
• Intermolecular interactions, particularly hydrogen bonding, play a significant role in dictating the crystal packing of these compounds.
• The findings contribute to the understanding of structure-property relationships in thiourea-based materials.