Synthesis, characterization and photophysics of novel BODIPY linked to dumbbell systems based on Fullerene[60]pyrrolidine and Fullerene[60]isoxazoline

Abstract

Pyrrolidine [60]Fullerene-BODIPY (BDP(Pyr)2) and Isoxazoline [60]Fullerene-BODIPY (BDP(Iso)2) are two C60 fragments linked in a dumbbell system to the boron-dipyrromethene core (BODIPY). We have synthesized and characterized these systems by NMR, MALDI-TOF, mass spectroscopy, and time-resolved spectroscopy. The photophysical properties of these novel compounds show a strong interaction in the excited state, generating charged species between BODIPY and the two C60 units. Furthermore, by employing cyclic voltammetry and pulse differential studies, we measured this electronic interaction: it is stronger in BDP(Iso)2 than in BDP(Pyr)2, likely due to the isoxazoline ring conjugation which increases the interaction between the electro-attractive units. This result is confirmed by fluorescence lifetime measurements, in which the BDP(Iso)2 shows a better performance even at different solvent polarities. Finally, we attribute the transitions of the HOMO→LUMO and HOMO→LUMO+1 orbitals to the maximum absorption wavelength, which produces the S1 and S2 excited states, respectively, for which the intramolecular charge transport is stronger between the BODIPY and the two C60 units.