Family of Quasi-Isotropic MnII and Mn2II Complexes Exhibiting Slow Relaxation of the Magnetization.

Abstract

Slow relaxation of magnetization has been studied for a family of mononuclear MnII complexes and one ferromagnetic dinuclear system, all of them presenting very weak anisotropy. Complexes with formula [{NiL1Mn(H2O)2(MeOH)}{NiL1}2](ClO4)2 (1), [Mn{NiL1}2](ClO4)2 (2), [Mn{NiL2}2](ClO4)2 (RR-L22-, 3RR, SS-L22-, 3SS), [Mn{NiL3}2](ClO4)2 (RR-L32-, 4RR, SS-L32-, 4SS) and (μ1,1-N3)2[Ni2Mn2(L1)2(N3)2] (5) are derived from compartmental Schiff bases, in which the NiII environment is square planar and thus diamagnetic. All of the systems have been structurally and magnetically characterized. Zero field splitting (D) values for the MnII cations have been obtained from EPR spectroscopy and NEVPT2 calculations. The slow relaxation of the magnetization for 1-5 has been studied by means of ac magnetometry and rationalized on the basis of their low, but not zero, anisotropy, providing the first example of a polynuclear MnII complex, with S = 5 ground state, exhibiting slow relaxation.