Singlet and triplet excited states of a series of BODIPY dyes as calculated by TDDFT and DLPNO-STEOM-CCSD methods.

The singlet and triplet excited states of three iodine substituted BODIPY dyes differing by their substituents (-phenyl, -phenylOH and -phenylNO2) at the meso position of the BODIPY core (BOD) are investigated using (TDA)-TDDFT and DLPNO-STEOM-CCSD calculations. An assessment of hybrid (B3LYP and MN15) and double hybrid (SOS-PBE-QIDH and SOS-ωPBEPP86) exchange-correlation functionals is performed with respect to the DLPNO-STEOM-CCSD method for four types of transitions, namely , , and . It is found that MN15 and SOS-PBE-QIDH provide a balanced description of the excited state energies when compared to the DLPNO-STEOM-CCSD results. An investigation of the effects of the solvent (dichloromethane), of the substituent and of geometrical relaxation in the excited states is then performed. In particular, the study discusses the possibility of populating charge transfer states ( and ) following photoexcitation in the first and second absorption bands in these systems.