The first one-dimensional iron phosphite - Phosphate, [Fe III(2,2â?²-bipyridine)(HPO3)(H2PO 4)]: Synthesis, structure, and magnetic properties

A hydrothermal reaction of a mixture containing iron powder, phosphorus acid, 2,2�-bipyridine, and water at 125 °C for 7 days gave colorless rods of a new hybrid iron phosphite-phosphate, [FeIII(2,2�- bipyridne)(HPO3)(H2PO4)], I. The structure consists of an edge-shared four-membered ring formed by the connectivity between FeO4N2 octahedra, pseudo-pyramidal HPO3 units. 2,2�-Bipyridine and PO2-(OH)2 tetrahedra are grafted onto the Fe center and hang into the interchain spaces. This is the first observation, to our knowledge, of a one-dimensional edge-shared chain structure in iron phosphite/phosphate. The structure appears to have close similarity to an iron arsenate-oxalate, [C4N2H 12][Fe(OH)-(HAsO4)(C2O4)] ·H2O, and a cadmium phosphate, [Cd(2,2�-bpy)(H 2PO4)2. Magnetic investigations reveal that the iron is present in the +3 oxidation state and shows antiferromagnetic interactions with typical low-dimensional behavior. The magnetic interactions between the Fe3+ ions are modeled using classical uniform chain solution with a single coupling constant J, formulated by Fisher involving nearest and next-nearest neighbor exchange interactions, based on the S = 5/2 Heisenberg antiferromagentic chain.