Experimental and numerical analysis of magnetic susceptibility of the tetranuclear heterometallic SMM complexes [Me2 IIFe2 III(L)4(OH)2⋅EtOH)2⋅(Et2O)2], Me = Co, Ni with dicubane structure

Abstract

Abstract Magnetic susceptibilities of the two isostructural heterometallic complexes, [Me2 IIFe2 III(L)4(OH)2,(EtOH)2,(Et2O)2], Me = Co, Ni, with triketonate ligands L = dianion of 1,1,1,7,7,7-hexa-fluoroheptane-2,4,6-trione, were studied experimentally and theoretically. Extended theoretical analysis included a phenomenological approach as well as quantum calculations in several numerical schemes. Magnetic ground states of Co2 IIFe2 III(L)4 and Ni2 IIFe2 III(L)4 complexes were resolved as an interplay of two intrinsic superexchange interactions with the constants J FeFe and J CoFe/J NiFe. The first system was described by two non interacting AFM-coupled pairs Co-Fe with J CoFe = - 4.2 cm−1 and zero-field splitting parameter D = -0.15 cm−1. The second one revealed the ferromagnetic coupling between the AFM dimers, J NiFe = -12.1 cm−1, J FeFe = 1.3 cm−1 and D = -0.5 cm−1.