Fe-57-M & ouml;ssbauer spectra of double MM'(C2O4)(2)& sdot;4H(2)O (M = Fe, M' = Mg, Co, Zn) and triple metal oxalates MM'M"(C2O4)(3)& sdot;6H(2)O (M = Fe, M' = Mg, Mn, Co; M" = Zn) were recorded at room temperature and briefly discussed on the basis of their structural characteristics. No changes in the hyperfine interactions at the Fe-57 site were detected because of the presence of the other metal ions.

The infrared and Raman spectra of barium oxalate hemihydrate, BaC2O4 center dot 0.5H(2)O, were recorded and discussed on the basis of their structural peculiarities and in comparison with the spectra of the previously investigated calcium and strontium oxalates.

Daniel Palacios1,2, Alejandra Wladimirsky1, Maria C.D’Antonio1,2, Ana C.González-Baró3, Enrique J.Baran3,* Departamento de Ciencias Básicas, UTN-Facultad Regional Santa Cruz, 9400-Río Gallegos, (ARGENTINA) Instituto de Tecnología Aplicada, Universidad Nacional de la Patagonia Austral, 9400-Río Gallegos, (ARGENTINA) Centro de Química Inorgánica (CEQUINOR, CONICET-UNLP), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, C. Correo 962, 1900-La Plata, (ARGENTINA) E-mail : baran@quimica.unlp.edu.ar

The infrared and Raman spectra of the two hydrates of strontium oxalate, SrC2O4⋅H2O and SrC2O4⋅2H2O, were recorded and discussed on the basis of their structural peculiarities and in comparison with the spectra of the related calcium oxalates and other previously investigated metallic oxalates.

The infrared and Raman spectra of CdC2O4iƒ—3H2O are recorded and discussed on the basis of their structural peculiarities and in comparison with the spectra of other previously investigated metallic oxalates. The spectra of the anhydrous CdC2O4 were also recorded, showing a totally similar spectroscopic behavior, and suggesting a closely related structural arrangement.

The infrared and Raman spectra of Na2Cu(C2O4)(2)·2H2O, K2Cu(C2O4)(2)·2H2O and (NH4)2Cu(C2O4)(2)·2H2O were recorded and briefly discussed on the basis of their structural peculiarities and by comparison with the vibrational spectra of other metallic oxalates.

The infrared and Raman spectra of anhydrous tin(II) oxalate, SnC2O4, were recorded and discussed on the basis of its structural peculiarities. Some comparisons with other previously investigated metallic oxalates were made.

The infrared and Raman spectra of anhydrous MgC2O4 as well as those of the two polymorphic forms of the dihydrated oxalate, α-MgC2O4·2H2O and β-MgC2O4·2H2O, were recorded and discussed on the basis of their structural peculiarities and in comparison with the spectra of natural α-MgC2O4·2H2O (the mineral glushinskite). Some comparisons between these polymorphs and with other, previously investigated, oxalate complexes were made. The IR spectra of partially deuterated samples of α-MgC2O4·2H2O were also discussed, reinforcing some of the performed assignments.

In an attempt to contribute to a better characterization of Fe-II and Fe-III oxalate complexes, an investigation of their vibrational (infrared and Raman) and Fe-57-Mossbauer spectra was performed. It is shown that the two polymorphs, alpha and beta, of FeC2O4 center dot 2H(2)O cannot be accurately differentiated with any of these spectroscopic methods, demonstrating the high structural similarity of these two crystalline forms. Partially deuterated samples of beta-FeC2O4 center dot 2H(2)O were also investigated to improve the vibrational-spectroscopic analysis. In the case of Fe-2(C2O4)(3)center dot 4H(2)O, a structural model, derived from results of combined vibrational and Mossbauer data, could be proposed. The 298 K Mossbauer spectrum for this complex is discussed in detail for the first time.

The infrared and Raman spectra of synthetic moolooite, Cu(C2O4)·nH2O, were recorded and analyzed on the basis of its structural characteristics and by comparison with related species. The thermogravimetric analysis of the investigated samples show that the water content n, was equal to 0.2. The electronic (reflectance) spectrum of the complex was also recorded and briefly discussed.