Noncovalent complexes between dimethyl ether and formic acid--an ab initio and matrix isolation study.

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Spectroscopy

Background:

• Noncovalent interactions are fundamental to molecular recognition and self-assembly.
• Understanding weak interactions in small organic molecules is crucial for predicting larger system behavior.
• Formic acid and dimethyl ether are simple molecules with potential for diverse intermolecular interactions.

Purpose of the Study:

• To investigate the complexes formed by noncovalent interactions between formic acid and dimethyl ether.
• To characterize the binding energies and interaction types of these complexes.
• To experimentally validate the strongest bound complexes using spectroscopy.

Main Methods:

• Ab initio quantum chemical calculations (MP2/cc-pVTZ) were employed to predict complex structures and binding energies.
• Corrections for zero-point vibrational energy and basis set superposition error were included.
• Matrix isolation spectroscopy was used to experimentally characterize the infrared spectra of the complexes.

Main Results:

• Six distinct complexes were identified with binding energies ranging from -2.26 to -7.97 kcal mol(-1).
• The two most stable complexes were found to be nearly isoenergetic, differing by less than 0.3 kcal mol(-1).
• Binding interactions were characterized as OH...O, C=O...H, C-O...H, and CH...O hydrogen and van der Waals bonds.

Conclusions:

• The study successfully identified and characterized multiple noncovalent complexes between formic acid and dimethyl ether.
• Matrix isolation spectroscopy confirmed the existence of the two most strongly bound complexes.
• The findings provide detailed insights into the nature and strength of intermolecular forces in this simple binary system.