2E→4A2 Luminescence and 4A2→2E, 2T1(t 32g) absorption spectra of the Cr(en) 3+3 ion

Abstract

The ⁴A₂→²E, ²T₁ Electronic absorption and the luminescence spectra of [Cr(en)₃](ClO₄)₃, 2Cr(en)₃Cl₃ . KCl . 6H₂O (en = 1,2 diaminoethane) and their deuterated analogues have been measured at temperatures down to 5 K. Comparison of these spectra with the infra-red spectra shows that there is strong interaction between the vibronic states involving the ²E(O) electronic state and the ²T₁(O) electronic state. The most intense vibronic origins in the luminescence spectra involve vibrational motions which cause a redistribution of electron density near the chromium atom. This provides information on the types of motion which contribute to particular vibrational frequencies. Contrary to a previous report, there is no evidence for the importance of a very low frequency vibration in the intensity mechanism of the ⁴A₂↔²E, ²T₁ transitions.