Results and Discussion
DFT Calculations
Since the geometry of berkelium carbonate complexes is unknown, we
firstly modelled the initial structures. Hobart and
coworkers2 suggested two different structures
according to their experimental studies varying the carbonate
concentration and pH, one corresponding to the homoleptic carbonate
complex and the second with coordination of hydroxyl ligands
(carbonate-hydroxide). Fig. 1 shows the two structures obtained by DFT
geometry optimizations with no symmetry constrains using a well-known
eight-coordinated structure of berkelium(IV), multiple starting
geometries were considered resulting always in structure 2 .
These structures correspond to a C2V and
quasi-C2V symmetry for 1 and 2 ,
respectively (Table S1, ESI). Because previously published experimental
absorption spectra of berkelium(IV) in carbonate solutions were
available, Time-Dependent DFT (TD-DFT) calculations were carried out to
understand the nature of the transitions responsible for the
charge-transfer band with a peak at 273 nm (Fig. 2).