BF2-Azadipyrromethenes: Probing the Excited-State Dynamics of a NIR Fluorophore and Photodynamic Therapy Agent

BF2-Azadipyrromethene dyes are a promising class of NIR emitter (nonhalogenated) and photosensitizer (halogenated). Spectroscopic studies on a benchmark example of each type, including absorption (one and two photon), time-resolved transient absorption (ps-ms) and fluorescence, are reported. Fast photodynamics reveal that intense nanosecond NW fluorescence is quenched in a brominated analog, giving rise to a persistent (21 mu s) transient absorption signature. Kinetics for these changes are determined and ascribed to the efficient population of a triplet state (72%), which can efficiently sensitize singlet oxygen formation (ca. 74%), directly observed by (1)Delta(g) luminescence. Photostability measurements reveal extremelz high stability, notably for the nonhalogenated variant, which is at least 10(3)-times more stable (Phi(photodeg). = < 10(-8)) than some representative BODIPY and fluorescein dyes.