Electron Paramagnetic Resonance Study of Copper− Ethylenediamine Complex Ion Intercalated in BentoniteReport as inadecuate

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This work reports on studies of two-dimensional networks of Cu2+ ions, built by exchanging Na-bentonite with Cu2+aqueous or with the bisethylenediamine complex, CuC2H4 NH222+, at different concentrations of the paramagnetic center.Dilution of the magnetically active species is performed by the cointercalation of analogous diamagnetic zinc species, aqueous Zn2+,or complexed ZnC2H4 NH222+ ions, with ethylenediamine in excess. Materials were characterized by X-ray diffraction, Fouriertransform infrared FT-IR and UV−visible spectroscopy, and continuous-wave electron paramagnetic resonance EPR. X-raydiffraction measurements indicated that the interlaminar distance in the bentonite decreases with the increase of Zn concentration inthe composites. The observation of a two-component Cu2+ EPR spectrum imply the coexistence of isolated Cu2+ with a wellresolvedhyperfine structure and spin−spin exchanged Cu2+ dimers or clusters with an unresolved hyperfine structure. EPR spinHamiltonian parameters of the isolated species in Cu-ethylenediamine intercalated samples are typical of axially distorted sites, sixcoordinatedwith bisethylenediamine in the equatorial plane and with oxygen on the internal surfaces of the clay. Experimentalfacts indicate that the interaction between paramagnetic centers is mainly favored by two different phenomena: turbostratic disorderof clay sheets and segregation of the magnetic centers leading to interstratifications of layers.Nota general

Artículo de publicación ISI

Author: Donoso, José Pedro; - Magon, Claudio J.; - Lima, José F.; - González Rees, Guillermo; - Nascimento, Otaciro R.; - Benavente

Source: http://repositorio.uchile.cl/


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