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).