Interactions between Thiourea and Imines. Prelude to Catalysis

Area of Science:

• Computational Chemistry
• Molecular Interactions
• Quantum Chemistry

Background:

• Thiourea is a versatile molecule with known hydrogen bonding capabilities.
• Imines are important functional groups in organic chemistry and biochemistry.
• Understanding non-covalent interactions is crucial for predicting molecular behavior.

Purpose of the Study:

• To investigate the interaction complexes between thiourea and a series of imines.
• To characterize the stable geometries and binding energies of these complexes.
• To analyze the structural consequences of thiourea-imine complex formation.

Main Methods:

• High-level ab initio calculations were employed.
• Potential energy surfaces were explored to identify stable minima.
• Geometries and interaction energies of various complex types were computed.

Main Results:

• Multiple stable complex geometries were identified, including those with symmetric NH···N hydrogen bonds and combined NH···N/CH···S hydrogen bonds.
• Interaction energies ranged from approximately 2 to 13.5 kcal/mol.
• Complex formation generally elongated the imine C-N bond, with some exceptions showing contraction.

Conclusions:

• Thiourea and imines form diverse stable complexes driven by hydrogen bonding and other non-covalent forces.
• The strength and nature of these interactions significantly impact molecular geometry.
• These findings contribute to the understanding of supramolecular chemistry and molecular recognition.