Communication
ChemComm
this difference is due mainly to the greater surface sensitivity of
KRJL acknowledges Imperial College London for the award
LEIS compared to RBS; the different alkyl chain lengths may play a of a Junior Research Fellowship, and thanks Prof. Tom Welton
part, although we expect this effect to be relatively unimportant. for his help and excellent guidance. SF acknowledges support
In addition, our results shed significant light upon a study of a from the EPRSC, EP/H006060/1 for the purchase of the LEIS
SILP model system, [Pt(NH3)4]Cl2 dissolved in [C2C1Im][C2OSO3] instrument. IJVG acknowledge support from the EPSRC, EP/
([C2OSO3]À = ethylsulfate).11 For SILP catalysis, the reaction is likely J021199/1. Dr Richard Matthews is thanked for his help with
to occur near to the ionic liquid–gas outer atomic surface (which the graphical abstract. Richard Fogarty is thanked for his help
minimises mass transfer limitations). Therefore, a surface-active with sample preparation.
catalyst will minimise the amount of catalyst needed in the system.
It was found that the soft Pt complex ions were enriched in the
Notes and references
1 (a) C. S. Santos and S. Baldelli, Chem. Soc. Rev., 2010, 39, 2136;
(b) K. R. J. Lovelock, Phys. Chem. Chem. Phys., 2012, 14, 5071.
2 H. Niedermeyer, J. P. Hallett, I. J. Villar-Garcia, P. A. Hunt and
surface layer, and ClÀ were depleted.11 The depletion of ClÀ
agrees with our results here; cation–Cl intermolecular inter-
actions are expected to be the strongest in this ion mixture. The
intermolecular interactions between [Pt(NH3)4]2+ and [C2OSO3]À
are likely to be weaker than the intermolecular interactions
between [C2C1Im]+ and [C2OSO3]À, leading to more [Pt(NH3)4]2+
in the surface layer than for an ideal surface.
T. Welton, Chem. Soc. Rev., 2012, 41, 7780.
3 (a) K. R. J. Lovelock, I. J. Villar-Garcia, F. Maier, H. P. Steinru¨ck and
P. Licence, Chem. Rev., 2010, 110, 5158; (b) C. Waring, P. A. J. Bagot,
M. L. Costen and K. G. McKendrick, J. Phys. Chem. Lett., 2011, 2, 12;
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4 H. H. Brongersma, in Characterization of materials, ed. E. N. Kaufmann,
Wiley, Hoboken, 2012, pp. 1–23.
5 I. J. Villar-Garcia, S. Fearn, G. F. De Gregorio, N. L. Ismail,
F. J. V. Gschwend, A. J. S. McIntosh and K. R. J. Lovelock, Chem.
Sci., 2014, DOI: 10.1039/C4SC00640B.
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7 A. Arce, M. J. Earle, S. P. Katdare, H. Rodriguez and K. R. Seddon,
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We have demonstrated using careful choices of ion mixtures
that the ionic liquid–vacuum outer atomic surface composition
can be very different to the ideal surface composition, allowing
one to fine-tune the ionic liquid–vacuum outer atomic surface
for different applications. For example, it is possible that the
kinetics of water adsorption would be slowed by adding a small
amount of [C4C1Im][Tf2N] to [C4C1Im]I, as adding a small
amount of [C4C1Im][Tf2N] to [C4C1Im]I would greatly reduce
the number of hydrogen bond acceptor adsorption sites at the ionic
liquid–vacuum outer atomic surface. In addition, our findings
advocate the use of catalysts with weaker cation–anion intermole-
cular interactions than the ionic liquid support, thus maximising the
amount of catalyst at the outer atomic surface. Finally, our results
show that low bulk amounts of ionic impurities may substantially
affect the surface chemistry of ionic liquids for any application.
8 R. Lungwitz, V. Strehmel and S. Spange, New J. Chem., 2010, 34, 1135.
9 K. R. J. Lovelock, J. P. Armstrong, P. Licence and R. G. Jones, Phys.
Chem. Chem. Phys., 2014, 16, 1339.
10 (a) A. Brandt, M. J. Ray, T. Q. To, D. J. Leak, R. J. Murphy and
T. Welton, Green Chem., 2011, 13, 2489; (b) M. A. Ab Rani, A. Brandt,
L. Crowhurst, A. Dolan, N. H. Hassan, J. P. Hallett, P. A. Hunt,
M. Lui, H. Niedermeyer, J. M. Perez-Arlandis, M. Schrems, T. Q. To,
T. Welton and R. Wilding, Phys. Chem. Chem. Phys., 2011, 13, 16831.
11 F. Maier, J. M. Gottfried, J. Rossa, D. Gerhard, P. S. Schulz,
W. Schwieger, P. Wasserscheid and H. P. Steinru¨ck, Angew. Chem.,
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5370 | Chem. Commun., 2015, 51, 5367--5370
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