Synthesis, structure and magnetic properties of a new iron arsenate, [C10N4H28][{FeF(OH)(HAsO4)}4], with a layer structure

The reaction of FeCl3.6H(2)O, HAsO4, HF and 1,4-bis(3-aminopropyl)piperazine under solvothermal conditions gives rise to a new iron arsenate, [C10N4H28]([FeF(OH)(HAsO4))}(4)] (I) with a layered structure. The cell parameters are monoclinic, space group = P2(1)/n (no.14), M = 1143.08, a = 9.6320(3), b = 8.3598(3), c = 10.7794(1) Angstrom, beta = 115.036(1)degrees, V = 786.42(4) Angstrom(3), Z = 4, R, = 0.0492, wR(2) = 0.1227 [1114 observed reflections with I > 2sigma(I)]. The connectivity between Fe2O3(OH) octahedra and HAsO4 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, SBU4. A dimer model has been used to describe the magnetic behavior. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.