Surface-Induced Changes in the Thermochromic Transformation of an Ionic Liquid Cobalt Thiocyanate Complex

May B, Hoenle M, Heller B, Greco F, Bhuin RG, Steinrück HP, Maier F (2017)


Publication Status: Published

Publication Type: Journal article

Publication year: 2017

Journal

Publisher: AMER CHEMICAL SOC

Book Volume: 8

Pages Range: 1137-1141

Journal Issue: 6

DOI: 10.1021/acs.jpclett.7b00142

Abstract

We demonstrate that a thermodynamic. complex equilibrium within an ionic liquid film can be significantly influenced by the presence of the liquid-vacuum interface. Using surface sensitive X-ray photoelectron spectroscopy, we find that the temperature-driven transition from the blue-colored tetrahedral [Co(II) (NCS)(4)](2-) to the red-colored octahedral [Co(II) (NCS)(6)](4-) complex already occurs within the outermost nanometers at around +4 degrees C as compared with -25 degrees C in the bulk. This thermochromic transformation in the near-surface region goes along with a loss in preferential surface orientation of free [SCN](-) anions and with a pronounced decrease in the complex density; both effects are attributed to the formation of a weakly bound solvation shell around the [Co(II) (NCS)(6)](4-) anion, leading to an effective complex dilution. Our results are not only relevant for high-surface area thin film systems, such as in sensor and catalysis applications, but also shed light on the role of ionic liquid surfaces in particular and liquid surfaces in general.

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How to cite

APA:

May, B., Hoenle, M., Heller, B., Greco, F., Bhuin, R.G., Steinrück, H.-P., & Maier, F. (2017). Surface-Induced Changes in the Thermochromic Transformation of an Ionic Liquid Cobalt Thiocyanate Complex. Journal of Physical Chemistry Letters, 8(6), 1137-1141. https://dx.doi.org/10.1021/acs.jpclett.7b00142

MLA:

May, Benjamin, et al. "Surface-Induced Changes in the Thermochromic Transformation of an Ionic Liquid Cobalt Thiocyanate Complex." Journal of Physical Chemistry Letters 8.6 (2017): 1137-1141.

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