Quantum-Chemical and IR Spectroscopic Study of Ionic Association in Solutions of LiCF3SO3 in Acetonitrile

• Published in: Russian Journal of Physical Chemistry A Vol. 94; no. 5; pp. 933 - 938
• Main Authors: Erkabaev, A. M., Yaroslavtseva, T. V., Bushkova, O. V.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01-05-2020; Springer Nature B.V
• Subjects: Acetonitrile; Chemistry; Chemistry and Materials Science; Fourier transforms; Infrared spectroscopy; Ion pairs; Ions; Lithium; Mathematical analysis; Physical Chemistry; Proceedings of the Conference “Physical Chemistry in Russia and Beyond: From Quantum Chemistry to Experiment” (Chernogolovka); Quadrupoles; Quantum chemistry; Spectroscopic analysis; Vibrational spectra; ionic association; quantum-chemical calculations; acetonitrile; lithium trifluoromethanesulfonate; nonaqueous solution; infrared spectroscopy
• ISSN: 0036-0244; 1531-863X
• DOI: 10.1134/S0036024420050064

The association of ions in solutions of  lithium trifluoromethanesulfonate in acetonitrile is studied via quantum chemistry and Fourier-transform infrared spectroscopy (FT-IR). Quantum-chemical calculations are performed using the attached-molecule approach, allowing for the influence of a polarized solvent medium for {Li
+
CF
3
SO
}
m
(CH
3
CN)
n
solvated neutral ionic associates (where
m
= 1 (ion pair) and 2 (ion quadrupole)). Vibrational spectra calculated at the RHF + MP2/6-311G** + SMD level of theory are used to identify ionic associates in IR spectroscopic studies of LiCF
3
SO
3
acetonitrile solutions (25°C and 0.05–1.28 mol/kg range of concentrations). {Li
+
CF
3
SO
}(CH
3
CN)
3
ion pairs are found in all solutions; {Li
+
CF
3
SO
}
2
(CH
3
CN)
2
ionic quadrupoles appeared at concentrations of ≥0.55 mol/kg. Characteristic changes in spectra of a CF
3
SO
polyatomic anion, due to different solvated ionic associates (ion pairs and quadrupoles), are observed.