Chemical states and lattice dynamics of alpha-diimine Fe2+ complexes intercalated into gamma-zirconium phosphate

The alpha -diimine Fe2+ complexes, [Fe(phen)(3)](2+), [Fe(bpy)(3)](2+), and [Fe(terpy)(2)](2+), (phen: 1,10-phenanthroline, bpy: 2,2'-bipyridyl, terpy : alpha,alpha',alpha " -tripyridine) were intercalated into zirconium dihyd rogenphosphate phosphate dihydrate (gamma -zirconium phosphate, gamma -ZrP) , Zr(PO4)(H2PO4) . 2H(2)O. The rate of the intercalation, the molar ratio o f Fe to Zr, was found to be 3.82-7.76%. Mossbauer spectra indicated that on e part of [Fe(phen)(3)](2+) and [Fe(bpy)(3)](2+) changed from a low-spin Fe 2+ to high-spin Fe2+ state on intercalation, but [Fe(terpy)(2)](2+) did not change in chemical state, The lattice dynamics of the complexes and the in tercalation compounds were investigated in terms of the temperature depende nce of the area intensity on the Mossbauer spectra, A linear relationship w as established for all the complex salts and the intercalation compounds in vestigated between the In[A(T)/A(82)] and absolute temperature, T, where A( T) and A(82) show the intensities of a doublet at T and 82 K of the Mossbau er spectra, respectively. From the slope of the linear relation, the Theta M-2 values, which were derived based on the Debye approximation of lattice vibration, were evaluated for the complex salts and the intercalation compo unds. The Fe2+ complexes showed Theta M-2 values of 1.27 to 2.32 x 10(6), w hereas the intercalation compounds showed very similar values to each other , ranging from 2.19 to 2.39 x 10(6), irrespective of different alpha -diimi ne ligands. The results were explained in terms of the characteristic layer ed structure of zirconium phosphate, and by the tight bond between the alph a -diimine Fe2+ complexes and the host gamma -ZrP.