Structure ofp-tetrafluorobenzoquinone: interaction with nematic liquid crystals

Abstract

The orientation of p‐tetrafluorobenzoquinone in four nematic liquid crystals with different aromaticities was determined by measuring the fluorine– fluorine and the fluorine– carbon scalar and dipolar couplings. Signs of the J(F,F) and the J(C,F) were determined without ambiguity. The experimental geometry was compared with those obtained by diffraction techniques and by ab initio molecular orbital calculations. Assuming a solvent– solute interaction potential based entirely on dispersion forces does not agree with experimental observations. The discrepancies are partly due to the formation of charge‐transfer molecular complexes. This latter contribution was confirmed by UV spectrophotometric measurements. Copyright © 2000 John Wiley & Sons, Ltd.

rαStructures of partially oriented pentafluorobenzenes C6F5X (X = H, Cl, I) as determined from19F NMR spectra with13C satellites

“…This does not mean that they are insignificant. As to the second interaction, complex formation with the ZLI 1695 solvent has been shown by means of UV spectroscopy for p ‐tetrafluorobenzoquinone, p ‐dibromotetrafluorobenzene and p ‐diiodotetrafluoro‐benzene 30. Therefore, we have performed a similar UV study on iodopentafluorobenzene with the intention of displaying a possible formation of charge transfer complex with the used anisotropic solvent.…”