Updates on Application of Silver Nanoparticles - Progress in Organic and Physical Chemistry: Structures and Mechanisms - page 114

a possibility of reduction of nicotinamidadenindinucleotid phosphate (NADP) and
methyl red dye (MR) connected with ɇ 2 Ɉ 2 the decomposition of photocatalyzed by
Chl was shown.
The coordination interaction between metal complexes of porphyrins, including
Chl, and hydrogen peroxide was detected. The kinetic parameters of photocatalytic
decomposition of ɇ 2 Ɉ 2 in the presence of Chl and metal porphyrins immobilized on
silica were studied. Photocatalytic activity of a number of non-transition metal por-
phyrins is shown to correlate with their ability to generate photopotential. Processes of
reduction of NADP and MR photocatalyzed by Chl in ɇ 2 Ɉ 2 solution are demonstrated.
Primary goal of our study is to show a possibility of reduction of electron acceptors
under photocatalytic decomposition of ɇ 2 Ɉ 2 .
9.2 EXPERIMENTAL
The Chl ' a' were separated by known method [6]. Individuality and concentration of
Chl were determined by UV-vis spectroscopy in quartz cells (1 cm) on hach dr/4000v
spectrophotometer. Metal complexes of TPP were synthesized and purified in Ivanovo
State University of Chemistry and Technology (Ivanovo, Russia). Hydrogen peroxide
and sodium bicarbonate (Reakhim, Russia) were used without additional purification.
Immobilizations of metal complexes on silica L 40/100 (Chemapol) were real-
ized by addition of silica (1 g) to the solutions of Chl in acetone and complexes of
TPP in chloroform. Suspensions were kept in the darkness to evaporate the solvent.
Samples were repeatedly washed out with distilled water and dried to constant weight
in vacuum exicator over CaCl 2 .
For kinetic experiments 10 ml of bicarbonate buffers (pH 8.5) containing 0.2 mol/l
ɇ 2 Ɉ 2 and 200 mg of silica with one of the supported complexes were placed in the
photochemical reactor. The obtained suspensions were irradiated by visible light us-
ing halogen lamp (150 W) with condenser and system of lenses at constant stirring.
Concentration of ɇ 2 Ɉ 2 was determined by titration method in 0.2 mol/l H 2 SO 4 medium
using 0.01 N KMnO 4 solutions. All experiments were carried out at 20°C. In the ex-
periments on reduction of electron acceptors the solutions of NADP (0.7·10 -4 mol/l)
or MR (8.1·10 -4 mol/l) were added to water suspension of supported Chl. In the ex-
periments with ɆR ethanol were added into reaction system. For determination of the
amount of acceptor reduced forms of their spectral characteristics were used. UV-vis
Ȝ max (water), nm (lgİ): 320 (3.77) for reduced NADP and Ȝ max (ethanol), nm (lgİ): 498
(2.68) for reduced MR [7].
9.3 DISCUSSION AND RESULTS
The Chl and metal complexes of TPP coordinate hydrogen peroxide according to the
electron adsorption spectra (Figure 1). Solutions of H 2 O 2 were sequentially added to
the TPP metal complex solutions (10 -5 mol/l) to concentrations from 10 -7 to 10 -3 mol/l.
We can see that changes in the electronic spectra are concerned with only increase or
decrease of the extinction in the bands and the isobestic point observation. All visible
bands are correspond to ʌ-ʌ* transitions. At the addition of H 2 O 2 energy parameters
of the bands do not change. This means that the place of coordination of hydrogen
peroxide molecule(s) is magnesium ion, but not the porphyrin macrocycle, since the