Solvation and stabilization of palladium nanoparticles in phosphonium-based ionic liquids: a combined infrared spectroscopic and density functional theory study.

Abstract : Analysis of infrared spectra of palladium nanoparticles (NPs) immersed in the tri-tert-butyl-R-phosphonium-based ionic liquids (ILs) demonstrates that both cations and anions of the ILs interact with the NPs. According to quantum-chemical simulations of these interactions, the binding energy of anions to the Pd6 cluster, taken as a minimal-size model of the NPs, increases from ∼6 to ∼27 kcal mol(-1) in the order [PF6](-)≈ [BF4](-) < [Tf2N](-) < [OTf](-) < [Br](-)≪ [TFA](-). In contrast, the binding energy for all types of the [Bu(t)3PR](+) cations slightly varies at about ∼22 kcal mol(-1) only moderately depending on the choice of the R moiety (n-pentyl, 2-hydroxyethyl, 2-methoxyethyl, 2-ethoxy-2-oxoethyl). As a result, the energies of interaction between a Pd6 cluster and various ion pairs, formed by the abovementioned counter-ions, follow the order found for the anions and vary from ∼24 to ∼47 kcal mol(-1). These values are smaller than the energy of addition of a Pd atom to a Pdn cluster (∼58 kcal mol(-1)), which suggests kinetic stabilization of the NPs in phosphonium-based ILs rather than thermodynamic stabilization. The results are qualitatively similar to the trends found earlier for interactions between palladium clusters and components of imidazolium-based ILs, in spite of much larger contributions of the London dispersion forces to the binding of the [Bu(t)3PR](+) cations to the cluster (up to 80%) relative to the case of 1-R-3-methylimidazolium cations (up to 40%).
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Submitted on : Friday, October 31, 2014 - 1:24:01 PM
Last modification on : Wednesday, March 27, 2019 - 3:56:02 PM

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Elena E Zvereva, Stefan Grimme, Sergey A Katsyuba, Vadim V Ermolaev, Daria A Arkhipova, et al.. Solvation and stabilization of palladium nanoparticles in phosphonium-based ionic liquids: a combined infrared spectroscopic and density functional theory study.. Physical Chemistry Chemical Physics, Royal Society of Chemistry, 2014, 16 (38), pp.20672-80. ⟨10.1039/c4cp02547d ⟩. ⟨hal-01079150⟩

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