7 research outputs found
BODIPY–Bacteriochlorin Energy Transfer Arrays: Toward Near-IR Emitters with Broadly Tunable, Multiple Absorption Bands
A series of energy
transfer arrays, comprising a near-IR absorbing
and emitting bacteriochlorin, and BODIPY derivatives with different
absorption bands in the visible region (503–668 nm) have been
synthesized. Absorption band of BODIPY was tuned by installation of
0, 1, or 2 styryl substituents [2-(2,4,6-trimethoxyphenyl)Âethenyl],
which leads to derivatives with absorption maxima at 503, 587, and
668 nm, respectively. Efficient energy transfer (>0.90) is observed
for each dyad, which is manifested by nearly exclusive emission from
bacteriochlorin moiety upon BODIPY excitation. Fluorescence quantum
yield of each dyad in nonpolar solvent (toluene) is comparable with
that observed for corresponding bacteriochlorin monomer, and is significantly
reduced in solvent of high dielectric constants (DMF), most likely
by photoinduced electron transfer. Given the availability of diverse
BODIPY derivatives, with absorption between 500–700 nm, BODIPY–bacteriochlorin
arrays should allow for construction of near-IR emitting agents with
multiple and broadly tunable absorption bands. Solvent-dielectric
constant dependence of Φ<sub>f</sub> in dyads gives an opportunity
to construct environmentally sensitive fluorophores and probes
Symmetrical and Nonsymmetrical Meso–Meso Directly Linked Hydroporphyrin Dyads: Synthesis and Photochemical Properties
A series
of a rigid meso–meso directly linked chlorin–chlorin,
chlorin–bacteriochlorin, and bacteriochlorin–bacteriochlorin
dyads, including free bases as well as ZnÂ(II), PdÂ(II), and CuÂ(II)
complexes, has been synthesized, and their absorption, emission, singlet
oxygen (<sup>1</sup>O<sub>2</sub>) photosensitization, and electronic
properties have been examined. Marked bathochromic shifts of the long-wavelength
Q<sub><i>y</i></sub> absorption band and increase in fluorescence
quantum yields in dyads, in comparison to the corresponding monomers,
are observed. Nonsymmetrical dyads (except bacteriochlorin–bacteriochlorin)
show two distinctive Q<sub><i>y</i></sub> bands, corresponding
to the absorption of each dyad component. A nearly quantitative S<sub>1</sub>–S<sub>1</sub> energy transfer between hydroporphyrins
in dyads, leading to an almost exclusive emission of hydroporphyrin
with a lower S<sub>1</sub> energy, has been determined. Several symmetrical
and all nonsymmetrical dyads exhibit a significant reduction in fluorescence
quantum yields in solvents of high dielectric constants; this is attributed
to the photoinduced electron transfer. The complexation of one macrocycle
by CuÂ(II) or PdÂ(II) enhances intersystem crossing in the adjacent,
free base dyad component, which is manifested by a significant reduction
in fluorescence and increase in quantum yield of <sup>1</sup>O<sub>2</sub> photosensitization
Deep-Red Emissive BODIPY–Chlorin Arrays Excitable with Green and Red Wavelengths
We
report here the synthesis and characterization of BODIPY–chlorin
arrays containing a chlorin subunit, with tunable deep-red (641–685
nm) emission, and one or two BODIPY moieties, absorbing at 504 nm.
Two types of arrays were examined: one where BODIPY moieties are attached
through a phenylacetylene linker at the 13- or 3,13-positions of chlorin,
and a second type where BODIPY is attached at the 10-position of chlorin
through an amide linker. Each of the examined arrays exhibits an efficient
(≥0.80) energy transfer from BODIPY to the chlorin moiety in
both toluene and DMF and exhibits intense fluorescence of chlorin
upon excitation of BODIPY at ∼500 nm. Therefore, the effective
Stokes shift in such arrays is in the range of 140–180 nm.
Dyads with BODIPY attached at the 10-position of chlorin exhibit a
bright fluorescence in a range of solvents with different polarities
(i.e., toluene, MeOH, DMF, and DMSO). In contrast to this, some of
the arrays in which BODIPY is attached at the 3- or at both 3,13-positons
of chlorin exhibit significant reduction of fluorescence in polar
solvents. Overall, dyads where BODIPY is attached at the 10-position
of chlorin exhibit ∼5-fold brighter fluorescence than corresponding
chlorin monomers, upon excitation at 500 nm
Bacteriochlorin Dyads as Solvent Polarity Dependent Near-Infrared Fluorophores and Reactive Oxygen Species Photosensitizers
Symmetrical,
near-infrared absorbing bacteriochlorin dyads exhibit
gradual reduction of their fluorescence (intensity and lifetime) and
reactive oxygen species photosensitization efficiency (ROS) with increasing
solvent dielectric constant ε. For the directly linked dyad,
significant reduction is observed even in solvents of moderate ε,
while for the dyad containing a 1,4-phenylene linker, reduction is
more parallel to an increase in solvent ε. Bacteriochlorin dyads
are promising candidates for development of environmentally responsive
fluorophores and ROS sensitizers
Amphiphilic BODIPY-Hydroporphyrin Energy Transfer Arrays with Broadly Tunable Absorption and Deep Red/Near-Infrared Emission in Aqueous Micelles
BODIPY-hydroporphyrin
energy transfer arrays allow for development
of a family of fluorophores featuring a common excitation band at 500
nm, tunable excitation band in the deep red/near-infrared window, and
tunable emission. Their biomedical applications are contingent upon
retaining their optical properties in an aqueous environment. Amphiphilic
arrays containing PEG-substituted BODIPY and chlorins or bacteriochlorins
were prepared and their optical and fluorescence properties were determined
in organic solvents and aqueous surfactants. The first series of arrays
contains BODIPYs with PEG substituents attached to the boron, whereas
in the second series, PEG substituents are attached to the aryl at
the <i>meso</i> positions of BODIPY. For both series of
arrays, excitation of BODIPY at 500 nm results in efficient energy
transfer to and bright emission of hydroporphyrin in the deep-red (640–660
nm) or near-infrared (740–760 nm) spectral windows. In aqueous solution of
nonionic surfactants (Triton X-100 and Tween 20) arrays from the second
series exhibit significant quenching of fluorescence, whereas properties
of arrays from the first series are comparable to those observed in
polar organic solvents. Reported arrays possess large effective Stokes
shift (115–260 nm), multiple excitation wavelengths, and narrow,
tunable deep-red/near-IR fluorescence in aqueous surfactants, and
are promising candidates for a variety of biomedical-related applications