Pt L2 and L3 Absorption Studies of Pt-doped Polymers

Janusz W. Sobczak 1Ewa Sobczak 2,3Mirosław Krawczyk 1Magdalena Hasik 4Alicja Drelinkiewicz 5,6

1. Polish Academy of Sciences, Institute of Physical Chemistry, Kasprzaka 44/52, Warszawa 01-224, Poland
2. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland
3. Polish Academy of Sciences, Center for Theoretical Physics (CFT PAN), al. Lotników 32/46, Warszawa 02-668, Poland
4. AGH University of Science and Technology, Faculty of Materials Science and Ceramics (AGH UST), Mickiewicza 30, Kraków 30-059, Poland
5. Jagiellonian University, Faculty of Chemistry, Ingardena 3, Kraków 30-060, Poland
6. Polish Academy of Sciences, Institute of Catalysis and Surface Chemistry, Niezapominajek 8, Kraków 30-239, Poland

Abstract

A new application of noble metals dispersed in polymer matrices as heterogeneous catalysts has been developed in recent years. By using x-ray absorption methods we have examined electronic states and local structure around Pt ions incorporated in electro-active polymers namely polyaniline (PANI), poly(o-toluidine) (POT), poly(o-methoxyaniline) (POM), polypyrrole (PPY) and an electro-inactive polymer poly(4-vinylpyridine) (PVP). The absorption spectra were measured using synchrotron radiation. Polymers were doped with platinum using appropriate precursor solutions of Pt+4 or Pt+2 compounds containing chlorine.

The Pt L3 and Pt L2 absorption edges in the samples studied contain information on the partial densities of unoccupied 5d electron states around Pt ion according to dipole selection rules. The energy position of the absorption maximum depends on valency of Pt ion and bond ionicity, as well. It was found out that the Pt+4 ions were partially reduced by electroactive polymers studied (PANI, POT, POM and PPY). In contrast, the Pt+4 ions doped in electro-inactive polymer PVP have not been reduced.

The Fourier analysis of the x-ray extended absorption structures revealed the nearest atomic shells around Pt ions in the sample studied. The main contribution is originated from Pt-Cl bond. The strong amplitude of Pt-Cl bond in case of Pt/PVP sample was evidence that the Pt+4 ion is surrounded by 6 chlorine ions. In contrast, the small amplitude of Pt-Cl bond in case of electro-active polymers can be interpreted as caused by active groups of the polymer chain bonded to Pt ions instead of chlorine ligands.

 

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Presentation: poster at 18th Conference on Physical Organic Chemistry, Posters, by Janusz W. Sobczak
See On-line Journal of 18th Conference on Physical Organic Chemistry

Submitted: 2006-05-30 10:49
Revised:   2009-06-07 00:44