Hybrid open-framework iron phosphate - Oxalates demonstrating a dual role of the oxalate unit

New inorganic-organic hybrid open-framework materials of the pbosphate-oxal ate family, [Fe-2(H2O)(2)(HPO4)(2)(C2O4) . H2O (I), [Fe-2(H2O)(2)-(HPO4)(2) (C2O4)]. 2H(2)O (II), [C3N2H12][Fe-2(HPO4)(2)(C2O4)(1.5)](2) (III), and [C3 N2OH12]Fe-2(HPO4)(2)(C2O4)(1.5)](2) (IV) have been synthesized hydrothermal ly in the presence of structure-directing amines. The amine molecules are i ncorporated in III and IV, whereas I and II are devoid of them. The oxalate units act as a bridge between the layers in all the compounds. The layers in I and II are entirely inorganic, being formed by FeO6 and PO4 units, whe reas in III and IV oxalate units constitute the inorganic layers and act as the bridge between these layers. Such a dual role of the oxalate: unit is unique and noteworthy The formation of two types of inorganic layers in I a nd III consisting of four-, six-, and eight-membered rings, indicates the i nterconversions between the various rings in the phosphate-oxalates to be f acile. All the phosphate - oxalates show antiferromagnetic ordering at low temperatures.