Pulse Radiolysis and Computational Studies on a Pyrrolidinium Dicyanamide Ionic Liquid: Detection of the Dimer Radical Anion

Journal Article · 06 March 2018 · Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory

DOI: https://doi.org/10.1021/acs.jpca.8b00978 · OSTI ID:1433984

Das, Laboni ^[1]; Kumar, Rahul ^[2]; Maity, Dilip K.  ^[2]; Adhikari, Soumyakanti  ^[3]; Dhiman, Surajdevprakash B. ^[4]; Wishart, James F.  ^[4]

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1. Bhabha Atomic Research Centre, Mumbai (India). Radiation & Photochemistry Division; Homi Bhabha National Inst., Anushaktinagar, Mumbai (India).
2. Homi Bhabha National Inst., Anushaktinagar, Mumbai (India).
3. Bhabha Atomic Research Centre, Mumbai (India). Radiation & Photochemistry Division
4. Brookhaven National Lab. (BNL), Upton, NY (United States). Chemistry Division

A pulse radiolysis study on pyrrolidinium cation based ionic liquids is presented here in this paper. Time-resolved absorption spectra for 1-methyl-1-propylpyrrolidinium dicyanamide (DCA) at 500 ns after the electron pulse show broad absorption bands at wavelengths below 440 nm and at 640 nm. In pyrrolidinium bis(trifluoromethylsulfonyl)imide (NTf₂) and tris(perfluoroethyl)trifluorophosphate (FAP) ILs, the transient absorption below 440 nm is much weaker. The absorption at 500 ns, which increases with wavelength from 500 nm to beyond 800 nm, was assigned to the tail of the solvated electron NIR absorption spectrum, since it disappears in the presence of N₂O. In the DCA IL, the presence of a reducing species was confirmed by the formation of pyrene radical anion. The difference in the transient species in the case of the DCA IL compared to other two ILs should be due to the anion, with cations being similar. In pseudohalide ILs such as DCA, radicals are formed by direct hole trapping by the anion (X^– + h⁺ → X•), followed by addition to the parent anion. Prediction of the UV/vis absorption spectra of the dimer radical anion by computational calculation supports the experimental results. The oxidizing efficiency of (DCA)₂•– and its reduction potential (E(DCA)2•–/(2DCA–)) have been determined.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0012704
• OSTI ID: 1433984
• Report Number(s): BNL-203525-2018-JAAM; TRN: US1802548
• Journal Information: Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory, Vol. 122, Issue 12; ISSN 1089-5639
• Publisher: American Chemical SocietyCopyright Statement
• Country of Publication: United States
• Language: English