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СOMPLEX FORMATION OF METALPHAEOPHYTINS WITH POLY-4-VINYLPYRIDINE HYDROGEL

УДК 547.979.7+0.26+541.427.49

Изучено комплексообразование между различными металфеофитинами и П4ВП методами электронной и γ-резонансной спектроскопиии.

Электронды және γ-резонансты спектроскопия әдістерімен әр түрлі металдыфеофитиндер мен П4ВП гидрогелі арасындағы комплекстердің түзілуі қарастырылған.

Abstract

Сomplex formation between various metal phaeophytins and poly-4-vinylpyridine was investigated by UV-VIS and γ-resonance spectroscopy.

Keywords: Porphyrins, phaeophytin, polymer-metalphaeophytin, cobaltphaeophytin, nickelphaeophytin

Introduction

Porphyrins attract great attention due to their important role in nature processes and wide range of application: medicine, catalysis, electronics etc.

This paper is dedicated to investigation of porphyrins obtained from Kazakhstan plant sources and its complex formation with metal ions and poly-4-vinylpyridinе (P4VPy) by UV-VIS and Messbauer spectroscopy [1, 2].

Experimental

Swelling coefficients were measured by weight method. Messbauer spectras were obtained by spectrometer SM-2201. UV VIS spectra were measured by JASCO UV-VIS 7580.

Results and discussions

Swelling kinetics of poly-4-vinylpyridine in ethanol and ethanol solution of phaeophytin was studied (Figure l). Equilibrium value of swelling coefficient K of P4VPy is lower in presence of porphyrin due to binding of components. At Figure 2, contraction of P4VPy gel in presence of different metal phaeophytins is shown. It can be seen that contraction is more expressed in case of nickel phaeoplytin. It is a result of coordination complex formation of P4VPy with metal ions. UV VIS spectra of porphyrin containing systems in dimethyl formamide (DMF) are presented at Figure 3.

At complex formation of phaeophytin with metal ions, where metal ions occupy centre of coordinating plain N4 with formation MN4 coordination pack it is observed batachrome shift and intensity of absorption band decrease in long wave field [3, 4].

These systems were studied by γ-resonance spectroscopy. Messbauer spectra of ironphaeophytin shows presence of Fe(III) with next parameters: Isomeric shift Is=0.43 (mm/s), quadrapole splintering Qs=0.47 (mm/s). At Figure 4, γ-resonance spectra of polymer-metalphaeophtin complex are shown. These spectra demonstrate the presence of two components with next parameters:

1. Is=0.39(mm/s), Qs=0,74 (mm/s), S=96%

2. Is=0,57(mm/s), Qs=1,13(mm/s), S=4%

Fig. 1. Swelling kinetics of P4VPy gel in ethanol (1) and in ethanol solutions of phaeophytin (2)

Fig. 2. Swelling kinetics of P4VPy gel in ethanol solutions of iron phaeophytin (1), cobaltphaeophytin (2) and nickelphaeophytin (3)

Fig. 3. UV-VIS spectra in DMF: Php (СPhp = 10-4 mоl/l) (1), Php (СPhp =1,5•10-5 mоl/l) (2), P4VPy-NiPhp (СPhp = 10-5 mоl/l ) (3), P4VPy-СоPhp (4)

Fig.4. Messbauer spectra of P4VPy – FePhp system

The first component have the value of Is close to value for iron-phaephytun but the quadrapole splintering have the remarkably higher value, showing the coordination between polymer and metalporphyrin. This interaction is verified also by presence of second component with high spin state iron (II). So, coordination of polymer with metalphaeophytin is accompanied with partial metal reduction.

Sharp change of quadrapole splintering Qs from 0,47 to 0,74 mm/s shows the remarkable change of the surrounding symmetry of iron ions. It may be the result of changing complex’s structure with release of iron ions from the plain of porphyrin macro cycle (Figure 5).

Fig.5. Scheme of complex formation of metalphaeophytin with P4VPy

Catalytic properties of P4VPy hydrogel-metalporphyrin complex in model decarboxilation reaction of sorrel acid were studied [5-7].

From Figure 6, where expense of permanganat plotted versus time, it can be seen, that more active catalyst is polymer complex of cobaltphaeophytin (curve 1)

Fig. 6. Decarboxilation reaction of sorrel acid in absence (3) and presence of polymer-metalphaeophytin complex: gP4VPy-CoPhp(1), gP4VPy-NiPhp (2)

Conclusion

Complex formation between poly-4-vinylpyrridine and different metal phaeophytins was studied by methods of UV-VIS and γ-resonance spectroscopy. It was shown that in these system complexes are forming due to coordination of nitrogen atom of P4VPy with metal ion of metalphaeophytins.

 

References

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