NUKLEONIKA 2013, 58(3):351-357

INTERACTION OF DIATOMIC MOLECULES WITH NICKEL IONS INSIDE THE CHANNELS OF HIGH SILICA ZEOLITES - AN EPR AND DFT STUDY

Tomasz Mazur, Katarzyna Podolska, Piotr Pietrzyk, Zbigniew Sojka

Faculty of Chemistry, Jagiellonian University,
3 R. Ingardena Str., 30-060 Kraków, Poland

Interaction of CO, NO, and O₂ diatomics with Ni^II and Ni^I ions dispersed in ZSM-5 zeolite was investigated by electron paramagnetic resonance (EPR) spectroscopy and density functional theory (DFT) modelling. The resulting adducts Ni^I-CO, Ni^II-NO, and Ni^I-O₂ were identified based on g-tensor parameters, obtained by computer fitting of the powder EPR spectra, and next ascertained by parallel relativistic DFT calculations of the corresponding g-tensor values. The structures of the Ni^I-CO, Ni^II-NO, and Ni^I-O₂ complexes were obtained by geometry optimization with the Kohn-Sham method. Binding of the diatomics was discussed in terms of the spin-pairing and electron density transfer events. Interaction of CO with Ni^I cations led to the pronounced change in the coordination and electronic structure of the Ni^I center, however, no redox processes were observed in agreement with the “innocent” nature of CO as a ligand. On the contrary, strong electron and spin density redistribution was observed upon NO and O₂ interaction (“non-innocent ligands”) leading to the formation of the bound nitrosonium NO^sigma+ and superoxo O₂^– species, respectively.

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