title: 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%).
authors.affiliation: A.E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Centre, Russian Academy of Sciences, Arbuzov str. 8, 420088 Kazan, Russia. zverevaelena@ymail.com skatsyuba@yahoo.com.
authors.forename: Elena E
authors.initials: EE
authors.lastname: Zvereva
authors.forename: Stefan
authors.initials: S
authors.lastname: Grimme
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Katsyuba
authors.forename: Vadim V
authors.initials: VV
authors.lastname: Ermolaev
authors.forename: Daria A
authors.initials: DA
authors.lastname: Arkhipova
authors.forename: Ning
authors.initials: N
authors.lastname: Yan
authors.forename: Vasili A
authors.initials: VA
authors.lastname: Miluykov
authors.forename: Oleg G
authors.initials: OG
authors.lastname: Sinyashin
authors.forename: Alexey
authors.initials: A
authors.lastname: Aleksandrov
mesh_terms: D003198:Computer Simulation; D052578:Ionic Liquids / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D008956:Models, Chemical; D008958:Models, Molecular; D010165:Palladium / Q000737:chemistry*; D010720:Phosphines / Q000737:chemistry*; D011789:Quantum Theory; D012997:Solvents / Q000737:chemistry; D013055:Spectrophotometry, Infrared / Q000379:methods*
chemical_list: D052578:Ionic Liquids; D007477:Ions; D010720:Phosphines; D012997:Solvents; D010165:Palladium; C044646:phosphine