Synthesis, structure and magnetic properties of organic-intercalated bimetallic molecular-based ferrimagnets (n-C_nH_(2n+1))PPh_3M~(II)Fe~(III)-(C_2O_4)_3, (M~(II) = Mn, Fe; n = 3-7)

摘要

Bimetallic tris-oxalato-salts (n-C_nH_(2n+1))PPh_3M~(II)Fe~(III)(C_2O_4)_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) an Fe~(III) bridged by oxalatet, with the organic cations lying between the metal-oxalate layers, whose separation ranges from 9.48 A (n = 3) to 11.10 A (n = 7) for the Fe~(II) salts and 9.37 to 10.81 A for Mn~(II). The compounds all behave as ferrimagnets, with magnetic parameters similar to the corresponding AM~(II)Fe~(III)(C_2O_4)_3 with A = NR_4~+, PPh_4~+ and T_cs almost insensitive to interlayer separation. The Mn~(II) salts exhibit uncompensated magnetisation below T_c and the Fe~(II) ones show Neel 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.