For the compounds under study, there were no significant differences from the choice of calculation parameters. The obtained molecular orbitals (with computational parameters corresponding to H2O) are shown in Figure . No profound relocation of charge density from BODIPY core to the substituent is visible (which would indicate PET-like behaviour). However, some charge is transferred to the nitrogen atom, possibly weakening the N-NO bond. The absence of PET is especially surprising because NO releaser described in , based on the same dye and N-nitroso bond as well, acts via PET mechanism. According to the authors, NO release process includes PET from the fragment containing N-NO to the BODIPY core and the formation of a radical pair.