An ARXPS and ERXPS study of quaternary ammonium and phosphonium ionic liquids: utilising a high energy Ag Lα' X-ray source.

A series of ammonium- and phosphonium-based ionic liquids have been probed using X-ray photoelectron spectroscopy (XPS) with a high energy Ag Lα' X-ray source. The capability of the Ag Lα' X-ray source for ionic liquid analysis is confirmed alongside the characterisation of previously undetected high energy core photoelectron emissions. Additionally, the utilisation of the Ag Lα' X-ray source as a depth profiling technique (ERXPS) to investigate the structure of the ionic liquid/vacuum interface has been demonstrated, with comparison made to angle resolved X-ray photoelectron spectroscopy (ARXPS).

XPS of guanidinium ionic liquids: a comparison of charge distribution in nitrogenous cations.

Herein, we investigate the first X-ray photoelectron spectroscopy (XPS) data for a range of functionalised guanidinium based systems that are commonly employed in the dissolution of biomolecules. We define a peak fitting model which allows the direct comparison to more common cation sets including dialkyl-imidazolium, pyrrolidinium, and quaternary ammonium based systems. The measured binding energies (BEs) of the N 1s and C 1s components are presented and notable variations discussed. These data show a large difference between measured binding energies for the Ncation 1s when compared to other families of ionic liquids. These results suggest a weaker anion/cation interaction thus the anion is more able to interact with a solid matrix, i.e. keratin, silk, chitin, collagen, cellulose, and become more active in dissolution.

Quaternary ammonium and phosphonium based ionic liquids: a comparison of common anions.

A series of ammonium-based ionic liquids and their phosphonium analogues have been investigated using X-ray Photoelectron Spectroscopy (XPS). A robust C 1s peak fitting model has been developed and described for the tetraalkylphosphonium and tetraalkylammonium families of ionic liquid, with comparisons made between the two series. Cation-anion interactions have been investigated to determine the impact of changing the cationic core from nitrogen to phosphorus upon the electronic environment of the anion. Comparisons between long and short chain cationic systems are also described.

Phosphoramidate synthesis via copper-catalysed aerobic oxidative coupling of amines and H-phosphonates.

The copper-catalysed oxidative coupling of amines and H-phosphonates to produce phosphoramidates has been achieved using CuI as the catalyst and O2 (present in air) as the sole oxidant.