PHOTOGENERATION OF SINGLET OXYGEN
1623
1
13
tEHTPP compound, 5.5%. TLC, Н, С-NMR spec-
The effective rate constants of tryptophan and
troscopy, and MALDI-TOF mass spectrometry were anthracene photooxidation were determined from the
used to identify compounds and determine their struc- initial parts of the kinetic curves, where the drop in
tures.
Anthracene (chemically pure grade) and D,L-
substrate concentration ΔC over period of observa-
s
tion Δt was ~20–30%, and calculated according to the
equation keff = ΔC C C Δt. The values of rate con-
s
s
P
tryprophan (pure grade) manufactured by AO
Reakhim (Russia) were used in photooxidation reac-
tions. Pluronic F-127 (Sigma-Aldrich, United States)
with a molecular mass of 12 600 was used for the solu-
bilization of PPS. UV spectra were recorded on a
Varian Cary 50 spectrophotometer.
stants were calculated from three experimental repli-
cates. The measuring error was ~10%.
RESULTS AND DISCUSSION
Photosensitization Activity of Substituted TPP
in the Oxidation of Anthracene in Chloroform
in with and without Pluronic F127
Solubilization of tetraphenylporphyrins with
pluronic was conducted by preparing a combined solu-
tion of polymer and porphyrin in chloroform with a
porphyrin concentration of 5.0 × 10−6 M (in experi-
ments on evaluating functional activity) and 3 × 10 М
in experiments on evaluating solubilizing activity),
and the concentration of pluronic was varied in the
The dependences of k for anthracene photooxi-
eff
dation in chloroform with TPP (curve 1) and substi-
tuted TPP (curves 2–4) on the pluronic F127 concen-
tration are presented in Fig. 3. Because THPP is insol-
uble in chloroform, the photocatalytic activity of the
−5
(
−6
−2
range 3.0 × 10 –3 × 10 M. The solution was evap- ethylene oxide derivatives of THPP in organic and
orated to dryness on a rotary evaporator, forming a aqueous phases was compared to the activity of unsub-
5
0–100-μm thick pluronic film with porphyrin stituted tetraphenylporphyrin, one of most effective
absorbed in it. Since the aim of this work was to pre- photosensitizers of singlet oxygen generation.
pare water-soluble porphyrin photosensitizers, the
It can be seen that with no pluronic F127, the
resulting film was dissolved in water, where the degree
mono- and di-substitutions in TPP reduced PPS
of solubilization was determined as the fraction of PPS
activity (the curves in Fig. 3), while tetra-substitution
molecules transferred to the aqueous phase as the
did not affect the porphyrin activity. The effective
films dissolved. Degree γ of PPS solubilization was
constant of photooxidation of anthracene for the
mono-substituted TPP in particular is 150% lower
calculated from the electronic absorption spectra
(
EAS) of porphyrins in water according to the equa-
than the k value for unsubstituted TPP, and 300%
eff
tion γ = CPw C , where C is the concentration of
porphyrin photosensitizer in the initial solvent (chlo-
Ps
Ps
lower for di-substituted TPP. The asymmetric substi-
tution (in mono- and di-substituted TPP molecules)
roform), and C is the concentration of PPS in water. that shifts the electron density and polarization of the
Pw
With THPP (which is poorly soluble in chloroform), porphyrin molecule obviously increases the PPS’s
solubilization was conducted by preparing combined propensity for aggregation.
solutions of PPS and pluronic in a chloroform–etha-
nol mixture (25 : 1). The concentration of solubilized
PPS was calculated from the intensity of the IV band
in the EAS that was affected least during solubilization
It is interesting that the pluronic has virtually no
effect on the photosensitization activity of TPP
curve 1) and tetra-substituted THPP (curve 4); the
(
levels of their activity are approximately the same. At
the same time, a 150% increase in activity upon a rise
in pluronic concentration is observed for the mono-
and di-substituted THPP (curves 2, 3). These porphy-
rins are obviously less soluble in chloroform than TPP
and tETHPP and were in an aggregated state. De-
aggregation occurs when the pluronic is present, and
the photocatalytic activity of the mono- and di-substi-
tuted TPP increases as a result. This agrees with the
increase in the intensity of the Soret band in the EAS
of dETHPP in chloroform with the pluronic (Fig. 2b,
curve 2).
(Fig. 2, 1–3).
The photooxidation reactions of substrates (thryp-
tophan in water and anthracene in chloroform) were
conducted a quartz cuvette (thickness l = 1 cm) with
mixing using an AFS phototherapeutic apparatus
manufactured by OOO Polironik (Russia) for illumi-
nation. The operating wavelength was λ = 400 nm, and
the power was 210 mW. The substrate concentration
−4
was C = 1 × 10 М, the PPS concentration was C =
s
P
−6
5
.0 × 10 М, and pluronic F-127 concentration C
Pl
−6
−4
was varied from 5 × 10 to 5 × 10 М. The kinetics of
tryptophan and anthracene photooxidation was mon-
itored using the drop in optical density at the UV
absorption bands of tryptophan in water (λ = 280 nm)
Determining the Degree of Solubilization
The electronic absorption spectra of TPP in chlo-
and anthracene in chloroform (λ = 360 nm). With roform with and without pluronic F127 and of TPPs
THPP (which is poorly soluble in chloroform), the solubilized with pluronic in water are presented in
photooxidation reaction was conducted in a chloro- Fig. 2а. We can see there is no change in the EAS of
form–ethanol mixture (25 : 1).
the unsubstituted TPP in chloroform with the
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 92 No. 8 2018