Synthesis, Structure and Magnetic Properties of a New Iron Arsenate, [C 10 N 4 H 28 ][{FeF(OH)(HAsO 4 )} 4 ], with a Layer Structure

The reaction of FeCl 3 ·6H 2 O, H 3 AsO 4 , HF and 1,4‐bis(3‐aminopropyl)piperazine under solvothermal conditions gives rise to a new iron arsenate, [C 10 N 4 H 28 ][{FeF(OH)(HAsO 4 )} 4 ] ( I ) with a layered structure. The cell parameters are monoclinic, space group = P 2 1 / n (no.14), M = 1143.08, a = 9.6320(3), b = 8.3598(3), c = 10.7794(1) Å, β = 115.036(1)°, V = 786.42(4) Å 3 , Z = 4, R 1 = 0.0492, wR 2 = 0.1227 [1114 observed reflections with I > 2σ( I )]. The connectivity between FeO 3 F 2 (OH) octahedra and HAsO 4 tetrahedra forms a secondary building unit (SBU) of the type SBU‐4. The SBU‐4 units are linked together to form a layer structure with apertures formed by 8‐T atoms (T = Fe, As). The amine molecules are disordered and occupy the inter‐lamellar region. To the best of our knowledge, I is the first example of an iron arsenate structure formed from only one type of secondary building unit, SBU‐4. A dimer model has been used to describe the magnetic behavior. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)