Quantum chemistry reveals a photoinduced cisoid to transoid rotation in the o-cobaltabis(dicarbollide) anion [o-COSAN]−, driven by the larger stability of the transoid rotamer in the excited triplet state. The non-radiative decay, supported by non-adiabatic molecular dynamics and the absence of signal in fluorescence mapping experiments, allows the thermal recovery of the dominant cisoid arrangement in water solution.
Cobaltabis(dicarbollide) anion ([o-COSAN]−) is a well-known metallacarborane with multiple applications in a variety of fields. In aqueous solution, the cisoid rotamer is the most stable disposition in the ground state. The present work provides theoretical evidence on the possibility to photoinduce the rotation from the cisoid to the transoid rotamer, a conversion that can be reverted when the ground state is repopulated. The non-radiative decay mechanisms proposed in this work are coherent with the lack of fluorescence observed in 3D fluorescence mapping experiments performed on [o-COSAN]− and its derivatives. This phenomenon induced by light has the potential to destruct the vesicles and micelles cisoid [o-COSAN]− typically forms in aqueous solution, which could lead to promising applications, particularly in the field of nanomedicine.