Cyclotriphosphazene-BODIPY Dyads: Synthesis, halogen atom effect on the photophysical and singlet oxygen generation properties

Abstract

Two new dendrimeric cyclotriphosphazenes (CBD 1 and CBD 2) bearing six BODIPY units functionalized with halogens were successfully designed and synthesized. Their photophysical properties including absorption and emission profiles, fluorescence quantum yield, and fluorescence lifetime were investigated. The dendrimeric cyclotriphosphazene-BODIPY systems displayed intense absorption bands at about 530 nm with good molar extinction coefficients and weak emissions owing to the presence of halogen atoms in the structures. We also determined the singlet oxygen (O-1(2)) formation abilities of the dendrimeric systems by chemical trapping and NIR phosphorescence methods. It was observed that the iodinated-BODIPY-cyclotriphosphazene dyad (CBD 1) was more efficient at generating O-1(2) than that of the brominated-dyad (CBD 2). Besides, both dendrimeric systems showed more remarkable photosensitization ability than some commonly used photosensitizer based on porphyrin and BODIPY derivatives.