Structural and dynamical features of the 2,2,2-trifluoroethanolammonia complex

Area of Science:

• Physical Chemistry
• Spectroscopy
• Computational Chemistry

Background:

• 2,2,2-trifluoroethanol (TFE) is a fluorinated alcohol with unique properties.
• Hydrogen bonding plays a crucial role in molecular complex formation and stability.
• Microwave spectroscopy is a powerful tool for determining molecular structures and interactions.

Purpose of the Study:

• To investigate the structure and bonding of the 1:1 adduct between 2,2,2-trifluoroethanol (TFE) and ammonia.
• To elucidate the conformational preferences and stabilizing interactions within the TFE-ammonia complex.
• To explore the internal dynamics of the complex using spectroscopic methods.

Main Methods:

• Chirped pulse and cavity-based Fourier transform microwave spectroscopy.
• Computational methods for analyzing rotational spectra and predicting structures.
• Isotopic substitution (deuterium and 15N) to confirm assignments and determine structures.

Main Results:

• Identification of the most stable gauche conformer of the TFE-ammonia adduct.
• Determination of partial rs and ro structures based on spectroscopic data.
• Observation of a complex interplay between O-HN hydrogen bonds and secondary N-HF interactions.
• Evidence of nearly free internal rotation of the ammonia subunit.
• Quenching of TFE's gauche-gauche tunneling by hydrogen bonding.

Conclusions:

• The TFE-ammonia adduct adopts a stable gauche conformation stabilized by a combination of hydrogen bonds.
• The study provides detailed structural and dynamic information about this molecular complex.
• The findings contribute to understanding non-covalent interactions in small molecular systems.