Nondiffusive Rotational Jump Dynamics in Ethyl Ammonium Nitrate

Area of Science:

• Physical Chemistry
• Materials Science
• Computational Chemistry

Background:

• Ionic liquids (ILs) exhibit unique properties due to their complex ion dynamics.
• Understanding hydrogen bonding in ILs is crucial for predicting their behavior and applications.
• Ethyl ammonium nitrate (EAN) is a representative protic ionic liquid with significant hydrogen bonding interactions.

Purpose of the Study:

• To elucidate the detailed mechanisms of hydrogen bond (H-bond) jumps in ethyl ammonium nitrate (EAN).
• To characterize the rotational dynamics associated with H-bond switching in EAN.
• To investigate the influence of temperature on these nondiffusive rotational dynamics.

Main Methods:

• Classical molecular dynamics (MD) simulations were employed to model EAN.
• Analysis focused on the N-H bond dynamics of the ethyl ammonium cation and nitrate anion interactions.
• Hydrogen bond jump angles and rotational mechanisms were quantified and analyzed.

Main Results:

• Two distinct nondiffusive rotational jump mechanisms for H-bonds were identified in EAN.
• Mechanism 1 involves switching between oxygen atoms of the same nitrate ion with an average jump angle of 30°.
• Mechanism 2 involves switching between oxygen atoms of different nitrate ions with an average jump angle of 70°, aligning with experimental observations.
• The rotation of the nitrate ion and the ammonium group were identified as key facilitators for each mechanism, respectively.
• Temperature variations were shown to affect the jump angles and their distributions, indicating temperature-dependent dynamics.

Conclusions:

• The study provides a detailed molecular-level understanding of hydrogen bond jump mechanisms in EAN.
• The identified mechanisms and their associated jump angles offer insights into the structure-dynamics relationship of ionic liquids.
• Findings contribute to the fundamental knowledge of ion transport and reactivity in ionic liquids.