Electron Lone-Pairs Stereochemistry and Drastic van der Waals and Pressure Effects in AsF3 from First Principles

Abstract

AsF3E as a representative of a molecular crystal has been chosen to find the precise localization of the lone pair (LP) E centroid 4s2 of As3+ and to enlighten the behavior of lone pair triplets of fluorine atoms. Starting from stereochemistry rationale, Density Functional (DFT) electronic structure calculations yielding the electron localization (ELF) mapping led to precise large crystal structure evolutions from basic X-rays data (V = 267.2Å3 at 193K), to (V = 230.5Å3) and under Van der Waals forces (DEW) V = 206.4Å3, and then under pressure P, all illustrated with ELF maps and band structures. Calibrated pressures up to 100 GPa exhibit the remarkable shrinking of all inter-atomic distances including As-E from 0.94Å down to 0.46Å, while the major three bonds As-F1, As-F2 and As-F3 are continuously expanding. The resulting picture of the application of pressure on AsF3 molecular structure leads to the progressive immersion of the 4s2 doublet within the electronic cloud with an original new status of As with its 4s2 E expressed as [AsE]3+. The expanded size becomes close to big LP-free K+, Ba2+ cations or LP characterized bismuth cation: [BiE]3+, which appear inserted in cubes or square anti-prisms with coordination number 8 (CN8) or in tricapped trigonal prisms with CN9.

Structural, dynamical, and electronic properties of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

“…An accurate analysis of the H-bonds is presented below. A more structured peaked shape is instead present in the anion–anion distribution, since the [TFSI] exposes O and F 47 atoms that carry electron-rich lone pairs and tend to form relatively strong H-bonds. We anticipate that these details will be clearer in the analysis of partial charges and the electronic structure given in paragraph 3.3.…”