The BODIPYs are versatile organic dyes which have found
wide applications in biological labeling and imaging,[0] luminescent devices,[0] chemical sensors,[0, 0] solar cells,[0] and photocatalytic hydrogen generation,[0] due to their excellent thermal
and photochemical stability, high fluorescence quantum yield,
intense absorption profile, good solubility, and chemical robustness. The intense absorption of BODIPYs in the near-infrared (NIR) region makes them suitable for PDT application, but
the low intersystem crossing (ISC) efficiency severely hampers
the ability to generate 0
O0 and thus the photodynamic activity
of BODIPYs. In 0000, O’Shea and co-workers successfully dealt
with this problem by introduction of bromine atoms into
a series of aza-BODIPYs to give the resulting dyes high 0
O0
quantum yields and potent photodynamic activity.[0] Recently,
Ramaiah and co-workers improved the 0
O0 quantum yields of
aza-BODIPYs further by attaching four iodine atoms on the dye
skeleton.[00] In 0000, Nagano et al. disclosed that an iodinated
BODIPY is also a good 0
O0 photosensitizer, but the examined
dye suffers from short absorption wavelength.[00] Akkaya et al.
extended the absorption bands of brominated or iodinated
BODIPYs into the phototherapeutic window by incorporating
conjugation structures at 0- and 0-positions of the BODIPY
core.[00] Recently, Ng and co-workers also reported a series of
unsymmetrical distyryl iodinated BODIPYs that show high in
vitro PDT activities.[00] Additionally, You and co-workers found
that fusion of brominated thiophene rings with the BODIPY
core may improve 0
O0 quantum yield remarkably.[00] While
much interest focused on the 0
O0 efficiency, absorption
window, and water solubility of the BODIPY family, another important factor, that is, the bioavailability of 0
O0, should also be
paid proper attention. 0
O0 is a highly reactive species but has
a short apparent lifetime (ca. 0.0 ms), a low apparent diffusion
coefficient (0 000 cm0 s), and thus a very limited sphere of activity (about 000 nm in radius) in biological systems, and this
implies the importance of the binding ability of PDT agents