Benzonitrile as a probe of local environment in ionic liquids
Shiguo Zhang1, Yan Zhang, Xiangyuan Ma
1Center for Green Chemistry and Catalysis, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China.
The Journal of Physical Chemistry. B
|February 13, 2013
Summary
Benzonitrile
Area of Science:
- Physical Chemistry
- Spectroscopy
- Materials Science
Background:
- Nitrile groups are sensitive IR probes for molecular environments.
- Ionic liquids (ILs) are versatile solvents with complex local structures.
- Understanding ILs' local structure and electric fields is crucial.
Purpose of the Study:
- To evaluate benzonitrile as an IR probe for monitoring IL local environments.
- To investigate the influence of IL structure on nitrile group vibrations.
- To determine the intrinsic electric field within ILs using vibrational spectroscopy.
Main Methods:
- Infrared (IR) spectroscopy of benzonitrile in imidazolium ionic liquids.
- Analysis of nitrile stretching vibration (νCN) band shifts and shapes.
- Application of vibrational Stark effect to quantify electric fields.
Main Results:
- νCN in non-hydroxyl ILs correlates with anion charge, unaffected by alkyl chain.
- Hydroxyl ILs show both free and H-bonded νCN bands.
- Benzonitrile preferentially probes the charged ionic network of ILs.
Conclusions:
- Benzonitrile's νCN is a reliable IR probe for ILs' local structure and electric fields.
- The method distinguishes between non-hydroxyl and hydroxyl IL environments.
- Benzonitrile is suitable for characterizing the ionic network in ILs.
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