Synthesis, structures and magnetic properties of two hexanuclear complexes

Abstract: The reaction of salicylaldoxime (H2salox) with Mn(ClO4)2 ·6H2O, NaN(CN)2 and NEt3 in MeOH affords a MnIII 6 hexanuclear complex of [Mn6O2(salox)6(MeOH)6(NCNCONH2)2] (1), while reaction of H2salox with MnCl2 ·4H2O and NEt4OH in EtOH affords a MnIII 6 hexanuclear complex of [Mn6O2(salox)6(EtOH)4(H2O)2Cl2] (2). Both complexes 1 and 2 contain a [MnIII 6(μ3-O)2]14+ core, which is a known structural type in the family of Mn6 complexes. Variable temperature magnetic susceptibilities and magnetization measurement of complexes 1 and 2 have been carried out. Exchange interactions of metal centers for complexes 1 and 2 are fitted by a full diagonalization matrix method. The fitting results indicate that both complexes 1 and 2 have the ground-state spin value of S =4, and the ground state of complex 1 has the much closer energy to low-lying spin states than that of complex 2. Magnetization measurements at 2.0–4.0K and 10–70kG confirm that the ground state is S =4, with significant magnetoanisotropy as gauged by the D value of −0.82cm−1 and −1.18cm−1, for 1 and 2, respectively. The frequency dependence of the out-of-phase component in alternating current magnetic susceptibilities for both complexes 1 and 2 indicates the slow magnetic relaxation of superparamagnetic behaviour with a U eff of 27.0(1)K and τ 0 =3.8(2)×10−9 s for complex 1, and U eff of 25.1(6)K and τ 0 =4.6(1)×10−8 s for complex 2. [Copyright &y& Elsevier]