Hybrid Open-Framework Iron Phosphate-Oxalates Demonstrating a Dual Role of the Oxalate Unit

Abstract

New inorganic-organic hybrid open-framework materials of the phosphate-oxalate family, [Fe 2 (H 2 O) 2 (HPO 4 ) 2 (C 2 O 4 )]H 2 O (I), [Fe 2 (H 2 O) 2 (HPO 4 ) 2 (C 2 O 4 )]·2H 2 O (II), [C 3 N 2 H 12 ] [Fe 2 (HPO 4 ) 2 (C 2 O 4 ) 1.5 ] 2 (III), and [C 3 N 2 OH 12 ] [Fe 2 (HPO 4 ) 2 (C 2 O 4 ) 1.5 ] 2 (IV) have been synthesized hydrothermally in the presence of structure-directing amines. The amine molecules are incorporated 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 FeO 6 and PO 4 units, whereas 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 and II consisting of four-, six-, and eight-membered rings, indicates the interconversions between the various rings in the phosphate-oxalates to be facile. All the phosphate-oxalates show antiferromagnetic ordering at low temperatures.