Luminescence and 4A2→2E, 2T1 absorption spectra of Cr(urea)6X3 . 3H2O(X = Cl, Br) and Cr(urea)6(NO3)3

Abstract

A re-examination of the luminescence and absorption spectra of the title compounds shows that the nitrate salt contains Cr(urea)⁶⁺₃ ions on at least five distinct lattice sites. These ions are excited both directly and by intermolecular energy transfer. In the bromide salt at least four of the ⁴A₂→²E, ²T₁ origins may be identified although there is appreciable interaction between the electronic and vibronic states involved. Although the ⁴T₂ electron origins occur a few hundred wave-numbers above the ²E origins, transitions to these levels are not definitely observed. There is no evidence for a Jahn–Teller effect in the ²E, ²T₁ states nor for appreciable magnetic coupling between the Cr(urea)³⁺₆ ions.