Development of infrared electroabsorption spectroscopy and its application to molecular structural studies

Area of Science:

• Spectroscopy
• Physical Chemistry
• Molecular Spectroscopy

Background:

• Infrared electroabsorption spectroscopy (IR-EAS) is a powerful technique for studying molecular properties under electric fields.
• Previous methods had limitations in sensitivity and applicability to liquid samples at room temperature.

Purpose of the Study:

• To develop a highly sensitive infrared electroabsorption spectroscopic system for analyzing liquids and solutions.
• To apply the system to investigate molecular behavior, conformational changes, and structural properties.

Main Methods:

• Construction of an AC-coupled dispersive infrared electroabsorption spectroscopic system.
• Measurement of electric-field-induced infrared absorption changes in the mid-infrared region (4000-820 cm(-1)).
• Application to liquid acetone, liquid 1,2-dichloroethane, and N-methylacetamide solutions.

Main Results:

• The system achieved high sensitivity, detecting absorption changes as small as 6 x 10(-8).
• Successfully observed orientational and electronic polarization signals in liquid acetone.
• Determined the gauche/trans ratio (1.4 +/- 0.2) and thermodynamic parameters for 1,2-dichloroethane.
• Clarified the head-to-tail structure of N-methylacetamide dimer and determined monomer/dimer dipole moments.

Conclusions:

• The developed IR-EAS system is effective for studying molecular dynamics and structures in liquids and solutions.
• The system provides valuable insights into conformational equilibria and intermolecular interactions.
• This technique offers a new avenue for detailed molecular characterization using infrared spectroscopy.