Synthesis, structure and magnetic properties of organic-intercalated bimetallic molecular-based ferrimagnets (n-CnH2n+1)PPh3MIIFeIII(C2O4)3, (MII = Mn, Fe; n = 3–7)

Abstract

Bimetallic tris-oxalato-salts (n-C_nH_2n+1)PPh₃M^IIFe^III(C₂O₄)₃ (n = 3–7, M^II = Mn, Fe) were prepared and the structures investigated by powder X-ray diffraction in order to study the evolution of the structure and magnetic properties as a function of alkyl chain length. The compounds all have the same two-dimensional honeycomb structure of M^II and Fe^III bridged by oxalate, with the organic cations lying between the metal–oxalate layers, whose separation ranges from 9.48 Å (n = 3) to 11.10 Å (n = 7) for the Fe^II salts and 9.37 to 10.81 Å for Mn^II. The compounds all behave as ferrimagnets, with magnetic parameters similar to the corresponding AM^IIFe^III(C₂O₄)₃ with A = NR₄⁺, PPh₄⁺ and T_cs almost insensitive to interlayer separation. The Mn^II salts exhibit uncompensated magnetisation below T_c and the Fe^II ones show Néel type N ferrimagnetism, with negative magnetisation at low temperature, the magnitude of which is influenced by the preparation conditions, due to vacancies in the Fe^II sublattice.