NIR BODIPY-Cyclotriphosphazene-Fullerene assemblies: Photophyisical properties and photosensitized generation of singlet oxygen

Two new, three component multimodular cis-tris-BODIPY-cyclotriphosphazene-cis-tris-fullerene systems (7 and 11) were designed and synthesized. In these derivatives, the triad bearing unsubstituted three-cis-BODIPY units (7) exhibited insolubility due to the appendment of three fullerenes on one molecule whereas the attachment of long alkyl chains enabled the solubility of the triad, distryl-BODIPY-cyclotriphosphazene-fullerene (11). The photophysical properties of the distryl-BODIPY-cyclotriphosphazene-fullerene (11) were investigated by means of absorption and fluorescence spectroscopies. As a result of extended conjugation, the distryl-BODIPY-cyclo-triphosphazene-fullerene triad (11) revealed absorbance and emission in the near-IR range in solution. The results are compared to those of the parent molecule, distryl-BODIPY-cyclotriphosphazene dyad system (10). Photoexcitation of the distryl-BODIPY-cyclotriphosphazene-fullerene triad (11) in solution results in quenching of emission. The fluorescence lifetime of triad 11 in solution is on the order of picoseconds. The triad (11) was also used as heavy-atom-free triplet photosensitizer for photooxidation of 1,3-diphenylisobenzofuran via the photosensitizing of singlet oxygen (O-1(2)) in three different solvents, dichloromethane, chloroform and acetonitrile. This multi-fragment donor-acceptor system demonstrated singlet oxygen production in all selected solvents.