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Issue 26, 2010
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Optical basicity of ionic liquids

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The concept of optical basicities initially developed by Duffy for solid oxides was successfully transferred to low melting salts such as ionic liquids (ILs). Several ionic liquids (ILs) were doped with Mn(NTf2)2 (NTf2 = bis(trifluoromethanesulfonyl)imide) as a probe to investigate the IL anion basicity by means of UV-Vis spectroscopy. The 6A14A, 4E(G) transition band of Mn2+ is influenced by the electron donor properties, i.e., Lewis basicity, of the coordinating ligands but remains—to the first order—independent from the ligand field. The change in the optical spectra for various Mn(NTf2)2 doped ILs is predominantly dependent on the anion. No significant influence of the IL cation could be detected for the ILs under investigation except for functionalized cations with electron donor functionalities. This allows ranking the ILs with respect to their (optical) anion basicities. For the most prominent IL anions an order of BF4 < ClO4 < NTf2 ∼ MeSO3 < NO3 < DCA < TFA < EtSO4 ∼ OTos < Cl < Br with respect to rising optical basicity could be established.

Graphical abstract: Optical basicity of ionic liquids

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The article was received on 04 Dec 2009, accepted on 08 Apr 2010 and first published on 18 May 2010

Article type: Paper
DOI: 10.1039/B925606G
Citation: Phys. Chem. Chem. Phys., 2010,12, 7056-7063

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    Optical basicity of ionic liquids

    S. Pitula and A. Mudring, Phys. Chem. Chem. Phys., 2010, 12, 7056
    DOI: 10.1039/B925606G

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