UCL Discovery

Abstract

Bimetallic tris-oxalato-salts (n-CnH2n+1)(PPh3MFeIII)-Fe-II(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 Angstrom (n = 3) to 11.10 Angstrom (n = 7) for the Fe-II salts and 9.37 to 10.81 Angstrom for Mn-II. The compounds ail behave as ferrimagnets, with magnetic parameters similar to the corresponding AM(II)Fe(III)(C2O4)(3) with A = NR4+, PPh4+ and T(c)s 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.