Synthesis and electronic properties of polycyclic aromatic hydrocarbons doped with phosphorus and sulfur

International audienc

XPS-evidence for in-situ electrochemically-generated carbene formation

Stable N-heterocyclic carbenes (NHC) are a class of compounds that has attracted a huge amount of interest in the last decade. One way to prepare NHCs is through chemical or electrochemical reduction of 1,3-disubstituted imidazolium cations. We are presenting an in-situ electrochemical X-ray Photoelectron Spectroscopy (XPS) study where electrochemically reduced imidazolium cations lead to production of stable NHC. The electroactive imidazolium species is not only the reactant, but also part of the ionic liquid which serves as the electrolyte, the medium and the electroactive material. This allows us to directly probe the difference between the parent imidazolium ion and the NHC through the use of XPS. The interpretation of the results is supported by both observation of reversible redox peaks in the voltammogram and the density functional theory calculations. © 2017 Elsevier Lt

Anionic states of six-membered aromatic phosphorus heterocycles as studied by electron transmission spectroscopy and ab initio methods.

The electron transmission spectra of 1,3,5-tri-tert-butyl-benzene, 2,4,6-tri-tert-butyl-pyridine, 2,4,6-tri-tert-butyl-phosphabenzene and 2,4,6-tri-tert-butyl,1,3,5-triphosphabenzene have been investigated and interpreted by means of quantum chemical calculations. Scaled virtual orbital energies obtained from calculations without employing diffuse functions provide good numerical values for the vertical electron attachment energies (VAEs). B3LYP/6-311+G* VAEs, calculated as the energy difference between the anion and the neutral molecule, were in good agreement with experiment, the molecules investigated here having VAEs of less than about 1 eV. The first anion state of phosphabenzene is predicted to lie at the edge of stability. The gradual replacement of CH units by phosphorus in p-systems results in a significant stabilization of the anionic states, which contrasts with the relative invariance of the electron donor properties. This behaviour can be explained by considering that for the P=C π-system both the interaction between the atomic levels (β) and the overlap is smaller than for the C=C π-system