The theoretical calculations on magnetic exchange of the title complex are carried out by using multiconfigurational second-order perturbation theory, CASPT2, and density functional theory combined with broken-symmetry approach, DFT-BS. The CASPT2 calculated quartet ground state, stabilized by 8.02 cm1 compared with the nearest excited doublet state, is close to 5cm 1 of the experimental measurement. The dependence of energy levels on the ratio J23/J12,13 validates occurrence of the spin frustration phenomenon. Both CASPT2 and DFT-BS calculations reproduce well experimentally coupling constants of J12, 13=9.35cm 1, J23=3.95cm 1, for CASPT2 J12, 13=6cm 1, J23=2cm 1 and for DFT-BS J12, 13=11.31cm 1, J23=4.20m 1. The methodological comparison is briefly discussed.

Two new complexes, 1 and 2, with halo acetate ligands have been prepared from the reaction of ClCH2CO2H or BrCH2CO2H with the precursor Mn12Ac, and their structures and magnetic properties studied. The structures of complexes 1 and 2 consist of a central cubane-like [Mn4O4]8 unit held within a non-planar ring of eight Mn4 by eight µ3-O ions, sixteen XCH2CO2 units and four terminal water molecules, as well as included CH2Cl2 and H2O. Dierent arrangements of the four Mn4 relative to the eight Mn4 comparable complexes could play a role in the observed magnetic properties. Five and three periodic steps in the magnetic hysteresis loops are observed for both 1 and 2 at 2.2 and 2.6K, respectively.χmT values for complexes 1 and 2, where χm is the in-phase component of the AC magnetic susceptibility, exhibit a plateau in the 6-20K region, below which there is an abrupt decrease in χmT. Their χm signals measured at different frequencies are observed in the region 2-10 K, and exhibit a frequency dependency on the χm AC peaks, with a predominant peak in the 4-10K region. For these complexes, there is a difference between the zero-field-cooled (ZFC) and the field-cooled (FC) magnetization due to slow relaxation of the magnetization.