X‐ray Photoelectron Spectroscopy of Pyridinium‐Based Ionic Liquids: Comparison to Imidazolium‐ and Pyrrolidinium‐Based Analogues

Abstract

We investigate eight 1‐alkylpyridinium‐based ionic liquids of the form [CnPy][A] by using X‐ray photoelectron spectroscopy (XPS). The electronic environment of each element of the ionic liquids is analyzed. In particular, a reliable fitting model is developed for the C 1s region that applies to each of the ionic liquids. This model allows the accurate charge correction of binding energies and the determination of reliable and reproducible binding energies for each ionic liquid. Shake‐up/off phenomena are determinedfor both C 1s and N 1s spectra. The electronic interaction between cations and anions is investigated for both simple ionic liquids and an example of an ionic‐liquid mixture; the effect of the anion on the electronic environment of the cation is also explored. Throughout the study, a detailed comparison is made between [C8Py][A] and analogues including 1‐octyl‐1‐methylpyrrolidinium‐ ([C8C1Pyrr][A]), and 1‐octyl‐3‐methylimidazolium‐ ([C8C1Im][A]) based samples, where X is common to all ionic liquids.

In‐Situ Nanostructuring and Stabilization of Polycrystalline Copper by an Organic Salt Additive Promotes Electrocatalytic CO2 Reduction to Ethylene

“…Analysis of the electrode surface, after bulk electrolysis using an electrolyte containing 1‐Br 2 , by X‐ray photoelectron spectroscopy (XPS), showed nitrogen enrichment (Figure S9). The spectrum consists of two peaks of similar area, located at 400.2 eV and 402.5 eV, characteristic of tertiary amine and quaternary ammonium nitrogen atoms, respectively . In addition, the surface of the electrode was rinsed several times with deionized water and then with DMSO‐d 6 .…”

“…Thes pectrum consists of two peaks of similar area, located at 400.2 eV and 402.5 eV,c haracteristic of tertiary amine and quaternary ammonium nitrogen atoms,r espectively. [31,32] In addition, the surface of the electrode was rinsed several times with deionized water and then with DMSO-d 6 . Theo rganic fraction was collected and analyzed by NMR spectroscopy.T he 1 Ha nd 1 H-1 HC OSY NMR spectra (Figures S10 and S11) acquired are consistent with the formation of two independent dimeric structures, para-para (1-Br) 2 and ortho-ortho (1-Br) 2 depicted in Figure 1b,derived from the coupling of two mono-reduced phenanthrolinium species (1C-Br)atthe para or ortho position, respectively.The amount of para-para coupled product is higher than the orthoortho product, as expected from the higher spin density at the para position of the precursor radical ( Figure S10).…”

Probing the electronic environment of binary and ternary ionic liquid mixtures by X-ray photoelectron spectroscopy

“…Over the past decade, X-ray photoelectron spectroscopy (XPS) has shown ability to reveal information, such as the elemental composition, surface enrichment, the subtle change of the electronic environment of a certain component present in an ionic liquid [9,10], the cation-anion interaction [11][12][13] and catalyst-ionic liquids interaction [14,15]. XPS analysis has also been used to provide detailed information on metal-based speciation formed in ionic liquids, through interaction between metal complexes and either the cation [14] or the anion [16] of ionic liquids.…”

Optical and XPS evidence for the electrochemical generation of an N-heterocyclic carbene and its CS2adduct from the ionic liquid [bmim][PF6]

“…Consistent with the literature data, only one N1s peak at 402.0 eV is observed representing the two equivalent nitrogen atoms of the imidazolium ring, but carrying one unit of positive charge. [63][64][65][66] The multiple structure of the S2p region is deconvoluted to three spin-orbit doublets; two of the major ones (designated as A and B in the figure) have binding energies assignable to the CS 2 adduct, but the third one (C) with much smaller intensity and at a higher energy position can best be assigned to oxidized sulfur atoms. One explanation for the appearance of two sulfur components can be given as partial conversion of CS 2 to OCS, either during generation of the adduct in air-ambient and/or transformation to the XPS chamber afterwards.…”

“…5), while revealing close to a stoichiometric compound. [63][64][65][66] View Article Online producing the carbene in the same mixture as above ex situ, thus hoping that the presence of CS 2 in the mixture would signal the carbene formation through appearance of the intense coloration. As expected and displayed in Fig.…”