Ionic liquids (ILs) are liquids composed entirely of ions. [1] Within the liquid the lack of single cation-anion associations, thus, the lack of ``ion pairing'' was suggested, [2] or at least a certain ion pairing deficiency due to structural mixture of ion-pairing with non-associative behavior, i.e. scale of ionicity,[3] as opposed to the vapor structure consisting of solely ion pairs. [4] Thus, depending on the definition of the term �ion pair� - especially in terms of time scales [2, 5] - the situations in which ion pairing might occur or can be fabricated may also alter. The importance of hydrogen or intermediate bonding in ionic liquids (ILs) has been recognized.[5] However, the term hydrogen bonding has to be treated with care, because depending on the kind of IL different intermediate interactions between cations and anions occur. In this presentation we discuss ion pairs in ionic liquids, and show different examples of changes in the structure or of the persistence. Furthermore, we show examples where hydrogen bonding in ionic liquids and even proton transfer takes place.[6] Mainly, we present mixtures of ILs, and CO2 absorbed in ILs. [6,7] We discuss interface and gas-phase conditions [8] and consider also a solute ion pair in ionic liquids [9].[1] Welton, T. Chemical Reviews 1999, 99, 2071-2084.[2] W. Zhao, F. Leroy, B. Heggen, S. Zahn, B. Kirchner, S. Balasubramanian, and F. M�ller-Plathe J. Am. Chem. Soc., 131 15825-15833, (2009); M. Y. Lui, L. Crowhurst, J. P. Hallett, P. A. Hunt, H. Niedermeyer and T. Welton Chem. Sci., 2011, 2, 1491�1496; J. P. Hallett, C. L. Liotta, G. Ranieri and T. Welton, J. Org. Chem., 2009, 74, 1864.[3] Tokuda, H.; Hayamizu, K.; Ishii, K.; Susan, M. A. B. H.; Watanabe, M. J. Phys. Chem.B 2004, 108, 16593-16600; Tokuda, H.; Hayamizu, K.; Ishii, K.; Susan, M. A. B. H.; Watanabe, M. J. Phys. Chem. B 2005, 109, 6103-6110.[4] J. M. S. S. Esperanca, J. N. Canongia Lopes, M. Tariq, L. M. Santos, J. W. Magee, L. P. N. Rebelo, J. Chem. Eng. Data 55, 3, 2010;[5] M. Kohagen, M. Brehm, J. Thar, W. Zhao, F. M�ller-Plathe, and B. Kirchner; J. Phys. Chem. B, 115 (4) 693-702, (2011)[6] O. Holl�czki, Z. Kelemen, L. K�ncz�l, D. Szieberth, L. Nyul�szi, A. Stark, B. Kirchner, ChemPhysChem, 14 315-320, (2013); O. Holloczki, D. S. Firaha, J. Friedrich, M. Brehm, R. Cybik, M. Wild, A. Stark, B. Kirchner, J. Phys. Chem. B, 117 (19) 5898-5907, (2013)[7] M. Br�ssel, M. Brehm, A. S. Pensado , F. Malberg, M. Ramzan, A. Stark, B. Kirchner, Phys. Chem. Chem. Phys., 14 13204-13215, (2012); M. Br�ssel, M. Brehm, T. Voigt and B. Kirchner; Phys. Chem. Chem. Phys., 13 13617-13620, (2011)[8] F. Malberg, A. S. Pensado, B. Kirchner, Phys. Chem. Chem. Phys. 14, 12079, 2012.; J. P. Leal, J. M. S. S. Esperanca, M. E. Minas da Piedade, J. N. Canongia Lopes, L. P. N. Rebelo, and K. R. Seddon J. Phys. Chem. A 2007, 111, 6176-6182[9] O. Holl�czki, F. Malberg, T. Welton and B. Kirchner, submitted

Ion pairing and hydrogen bonding in ionic liquids

248th National Meeting (2014)

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