Fig. 2. Experimental UV-vis absorption spectra (redrawn from reference 2) of Bk(IV) in 5 M (left) and 2 M (left) potassium carbonate solutions. Blue lines represent transitions predicted by TD-DFT for [Bk(CO3)4]4-(left) and [Bk(CO3)3(OH)2]4-(right).
From the calculated spectra, it is possible to assign the band-decomposition of the spectra for both structures, wherein both cases are assigned to ligand-to-metal charge transfers (LMCT). However, the intense transition at 370.9 nm in the carbonate-hydroxide spectrum corresponds to a mixed molecular orbital involving sigma contribution coming from both carbonate and hydroxyl ligands.
Table 1. Selected TD-DFT transitions representing the LMCT band in the absorption spectra for 1 and 2 . The transitions presented are those with the highest oscillator strengths (f).