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From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
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Ab Initio Study of Structural Features and H-Bonding in Alkylammonium-Based Protic Ionic Liquids
Irina V Fedorova1, Michael A Krestyaninov1, Lyubov P Safonova1
1G. A. Krestov Institute of Solution Chemistry of the Russian Academy of Sciences , 1 Akademicheskaya Street, Ivanovo 153045, Russia.
The Journal of Physical Chemistry. A
|October 3, 2017
Summary
Protic ionic liquids (PILs) formed from alkylammonium cations and various acid anions exhibit stronger hydrogen bonding with increased ethyl groups. This leads to ion pair formation and proton transfer, influenced by acid strength and solvation effects.
Area of Science:
- Physical Chemistry
- Computational Chemistry
- Materials Science
Background:
- Protic ionic liquids (PILs) are salts that are liquid at ambient temperatures, formed by proton transfer from an acid to a base.
- Understanding the structure-property relationships in PILs is crucial for their application in various fields.
- Computational methods offer a powerful approach to investigate the fundamental interactions within PILs.
Purpose of the Study:
- To investigate the structural and energetic characteristics of PILs with varying alkylammonium cations and acid anions.
- To elucidate the role of hydrogen bonding in the formation of molecular complexes and ion pairs.
- To examine the influence of alkyl chain length and acid strength on proton transfer and solvation effects.
Main Methods:
- Density functional theory (DFT) calculations at the B3LYP/6-31++G(d,p) level of theory were employed.
- Analysis of hydrogen-bonded molecular complexes and ion pairs formed between cations and anions.
- Investigation of proton transfer phenomena between different species.
- Application of the conductor-like polarizable continuum model (CPCM) to study solvation effects.
Main Results:
- The formation of hydrogen-bonded molecular complexes and ion pairs was observed.
- Increasing the number of ethyl groups on the ammonium cation enhanced hydrogen bonding interactions.
- Stronger hydrogen bond donor ability of the acid also strengthened the interactions, favoring ion pair formation.
- Proton transfer between ion pairs and molecular complexes was confirmed for all studied systems.
- Solvation effects were found to influence the stability and interactions within the PILs.
Conclusions:
- The strength of hydrogen bonding in PILs is tunable by modifying the cation's alkyl substitution and the acid's proton donating ability.
- Proton transfer is a key characteristic influencing the behavior of these PILs.
- Computational modeling provides valuable insights into the molecular-level interactions governing PIL properties.
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