In situ coordination of Fe2+ to aromatic diamines intercalated into γ-zirconium and γ-titanium phosphates: evidence from Mössbauer spectroscopy and thermal studies

Abstract

Iron(ii) can be exchanged into layered γ-Zr(H ₂ PO ₄ )(PO ₄ )–diamine and γ-Ti(H ₂ PO ₄ )(PO ₄ )–diamine composites (diamine=2,2′-bipyridyl, 1,10-phenanthroline, 2,9-dimethyl-1,10-phenanthroline). Mössbauer spectroscopy indicates that an in situ iron–amine coordination occurs in the case of iron–bipyridyl– and iron–phenanthroline–γ-zirconium phosphate: Fe ²⁺ low-spin trischelates [Fe(bipy) ₃ ] ²⁺ and [Fe(phen) ₃ ] ²⁺ are formed between the layers of the host; high-spin Fe ²⁺ also forms complexes in the interlayer region and the chromophores could be any of the possibilities provided by the formulation [FeN _x O _6-x ] (x=1–4). Iron(ii) partially transforms into iron(iii) when the former is not stabilized by the formation of strong complex species. The thermal behaviour of the exchanged compounds has been investigated and correlated with the composition of the materials. X-Ray patterns of some of the new materials are also reported.