Inner Shell Excitation Spectroscopy of Biphenyl and Substituted Biphenyls:  Probing Ring−Ring Delocalization

Abstract

Quantitative optical oscillator strength spectra for C 1s excitation and ionization of gas-phase biphenyl, decafluorobiphenyl, and 2,2'-bis(bromomethyl)-1,1'-biphenyl have been derived from electron energy loss spectroscopy recorded under electric dipole dominated conditions. The C 1s X-ray absorption spectrum of hexaphenylbenzene has been recorded in the solid state. The C 1s spectral features are interpreted with the aid of ab initio calculations for core excitation of benzene, biphenyl, hexafluorobenzene, and decafluorobiphenyl. A weak feature at 287.7 eV in biphenyl is identified as a C 1s --> pi(deloc) transition, characteristic of ring-ring delocalization. Its intensity and position are shown to be related to the average torsion angle and thus the extent of pi-pi-interaction between adjacent aromatic rings. The effects of perfluoro substitution on core excitation spectra are also characterized and discussed.

Unoccupied electronic states in polythiophene as probed by XAS and RAS

“…[10,11] Similar localizations have also been reported in the gas phase. [12,13] We measured RAS of PT as a function of photon energy to investigate more details of such delocalization. S KL 2,3 L 2,3 RAS spectra of PT are shown at typical energies in Fig.…”

Shape‐Switchable Azo‐Macrocycles

“…[161][162] Biphenyl derivatives have been considered as potential conductance switches rings can be either in the same plane or perpendicular to each other representing [163]- [165] In Figure 8 the two different states are shown depending on the conformation of the two phenyl rings. The torsion angel between the two phenyl rings of a biphenylic system is not at all fixed, it is very sensitive to its chemical environment and the substitution pattern.…”

“…[161][173] From a chemical point of view biphenyls are also interesting due to their easy synthetic accessibility via various cross coupling reactions. [149] The degree of -electron delocalization between the two phenyl units is expected to vary with the interplanar torsion angle .…”

Electronic structure of biphenyl on Si(100)

“…The torsional angle and the electronic interaction between the phenyl rings depend on the local environment. 13 Studying the adsorption of biphenyl on Si͑100͒ turns out to be a challenge for spectroscopic methods to elucidate the electronic structure and adsorption configurations of organic molecules on semiconductor surfaces. Despite the fact that biphenyl on Si͑100͒ is a simple system, it is much more complicated than benzene on Si͑100͒ ͑Ref.…”