Fig. 1. Possible schematic network structures of [M1M2(ox)3]n-: two-dimensional honeycomb (left) and three-dimensional helical (right) structures.
Heat capacities of the metal-assembled complex PPh4[MnIIFeIII(ox)3] (Ph: phenyl, ox: oxalato) were measured by adiabatic and relaxation methods. A broad magnetic thermal anomaly with a wide hump centered around 30 K accompanying a small shoulder around 23 K was observed. Magnetic entropy amounted to 33.1 J K-1 mol-1, which agrees well with the expected value for two S = 5/2 spin systems Rln(6×6) = 29.8 J K-1 mol-1. Magnetic measurements revealed that this complex is a canted antiferromagnet with an antiferromagnetic phase transition at TN = 23.0 K.
Fig. 1. Possible schematic network structures of [M1M2(ox)3]n-: two-dimensional honeycomb (left) and three-dimensional helical (right) structures.
Fig. 2. Heat capacities of PPh4[MnIIFeIII(ox)3] by adiabatic calorimetry (upper) and relaxation method under magnetic fields (lower).
Fig. 3. Magnetic heat capacities of PPh4[MnIIFeIII(ox)3] by adiabatic calorimetry (upper) and relaxation method under magnetic fields (lower). Red curve indicates the theoretical curve for high-temperature expansion of antiferromagnetic Heisenberg model for two-dimensional honey-comb lattice with J/kB = −5.0 K.