Charge transfer spectra of mono-substituted oxo-ions: low-temperature polarised absorption spectra and magnetic circular dichroism

Abstract

The polarised absorption spectra of CrO₃X^–(X = F or Cl) and OsO₃N^– doped in crystals of KClO₄ have been measured at 4 K. The guest ions are oriented in the host lattice by the C_x crystal field at the perchlorate ion sites, so that the observed dichroic ratios lead to assignments of the bands to ¹A₁or ¹E states of the C_3v oxo-ions. For the CrO₃X^– ions the assignments are confirmed by analysing the room temperature solution m.c.d. spectra. The lowest energy charge transfer configurations of all three ions are formed by donation of an electron from a₂, and e orbitals almost entirely localised on the oxygen atoms, which correlate with t₁ in the parent tetraoxo-ions.