Chemistry Reference
In-Depth Information
Fe(III)-phthalocyanine with a distorted rhombic coordination structure are active in
hydrogen peroxide decomposition that is also characteristic for catalase or peroxidase.
It was found that Fe(III)-octacarboxyphthalocyanine supported on an amorphous con-
centrated ¿ ber of arti¿ cial silk core element is a remarkably effective catalyst for the
decomposition of hydrogen peroxide [1]. Both phthalocyanines in a solution of con-
centrated sulfuric acid and polymeric structure of phthalocyanines have the catalase
activity. Phthalocyanines with metals of VIIIB group have the largest activity. Kinetic
data for the H
2
O
2
decay catalyzed by phthalocyanines, for a large number of metal
complexes are summarized in [2, 3].
However, high rate constants of excited states radiationless deactivation are ob-
served for complexes of tetrapyrrole macrocycles with open
d
-shell metals because of
strong exchange interaction between metal unpaired electron and tetrapyrrole ligand
molecular orbitals [4]. In contrast, complexes of porphyrins and phthalocyanines with
non-transition metals (Mg, Al, and Zn) are capable to generate long-lived (up to 1 ms)
triplet excited states with high quantum yield (60-90%) [5]. So, it is possible to realize
light controlled processes in the presence of these metal complexes. Chlorophyll (Chl)
also belongs to this group of tetrapyrrolic compounds, because its molecule contains
a magnesium ion.
The study of the catalytic activity of adsorbed Chl and phthalocyanines-metal
complexes in the hydrogen peroxide decay could be used for photodynamic therapy,
arti¿ cial photosynthesis and molecular photonics [3, 6]. In this regard, the catalytic
and photocatalytic activity of Chl and metal phthalocyanines adsorbed on silica in the
H
2
O
2
decomposition were investigated in this chapter. Alluminum (AlClPc) and zinc
phthalocyanine (ZnPc) were used as an analogue of Chl, since their photophysical
and photochemical properties are close to those of Chl, while their stability is much
higher [3].
10.2 EXPERIMENTAL
The Chl was isolated and purified from dry nettle leaves by chromatography on a
column with powdered sugar heated up at 100°C within 4 hr preliminary [7, 8]. The
Chl mix was solved in hexane-ether system (3:7) and put on a column. Elution was
realized by the same solvent system to distribute of pigments on the column fully. A
fraction painted by Chl
ɚ
was mechanically taken, and then it was washed off by ether.
Individuality and concentration of Chl
ɚ
were determined by UV-vis spectroscopy in
quartz cells (1 ɫm) on spectrophotometer DR/4000V (Hach, USA). Found and litera-
ture [9] spectra of Chl were identical.
The Chl
a
.
λ
max
(ether) nm (lg
ε
): 662 (4.96), 615 (4.14), 578 (3.88), 533.5 (3.57),
430 (5.08), and 410 (4.88).
The AlCl and Zn phthalocyanine complexes were synthesized and puri¿ ed in Iva-
novo State University of Chemistry and Technology (Ivanovo, Russia).
Equilibrium adsorption of Chl
and MPc complexes on silica L 40/100 (Chemapol)
was realized by addition of silica (1 g) to solutions of Chl in acetone, MPc complexes
in N, N-dimethylformamide (“Fluka”). Concentration of solutions was varied for pre-
paring of samples with different value of adsorption. Suspensions were in the dark for
24 hr with constant stirring. Recorded optical density of solutions at wavelength 674
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