4A2g↔2Eg transitions in trans-Cr(en)2Cl2+ and trans-Cr(tmd)2Cl +2

Abstract

The 80 K absorption and emission spectra of trans-[Cr(en)₂Cl₂] Cl · HCl · 2H₂O (en = 1,2-diaminoethane) and trans-[Cr(tmd)₂Cl]ClO₄(tmd = 1,3-diaminopropane) show extensive structure in the 13 000–16 000 cm^–1 region. Analysis of each absorption spectrum indicates the presence of two electronic origins separated by 210 and 239 cm^–1, respectively. The assignments of these bands and similar features in the spectra of other chloro-amine chromium(III) complexes are discussed with the help of “complete” crystal field calculations. The balance of the evidence supports their assignment as transitions from the ⁴A_2g(O_h) state to the split components of the ²E_g(O_h) state although the splitting is several times larger than the calculated value.