The SMM properties of the spatially closed Dy(Ⅲ) double-decker Pc complex Dy(obPc) 2 (1), which is equivalent to a pseudo dinuclear complex, are reported. Complex 1 crystallized with ethanol in the crystal lattice in the monoclinic space group P21/n and was isomorphous with Tb(obPc) 2 (3), which is arranged in a dimer structure along the b axis. The intermetallic Dy-Dy distance was determined to be 0.756 nm. χM T versus T plots for 1 decreased with a decrease in T, which suggests the existence of an antiferromagnetic (AF) interaction between the Dy 3+ ions. The M-H curve for 1 at 1.8 K showed magnetic hysteresis. In ac susceptibility measurements on a powder sample of 1, which were dependent on the applied ac field, indicating that 1 is an single molecule magnet (SMM), a maximum appeared at 22 K at an ac frequency (f) of 1488 Hz. The shape of the peaks drastically changed, and the peaks did not shift when an H dc large enough to suppress the quantum tunneling of the magnetization (QTM) was applied. The energy barrier (△/hc) was estimated to be 44 cm-1 with a pre-exponential factor (τ0 ) of 1.6 × 10 -5 s from an Arrhenius plot. Our results suggest that the SMM/magnetic properties of 1 significantly change in a dc magnetic field. These relaxation mechanisms are related to the energy gap of the ground state and to QTM. The SMM properties of the spatially closed Dy (III) double-decker Pc complex Dy (obPc) 2 (1), which is equivalent to a pseudo dinuclear complex, are reported. Complex 1 crystallized with ethanol in the crystal lattice in the monoclinic space group P21 / n and was isomorphous with Tb (obPc) 2 (3), which is arranged in a dimer structure along the b axis. The intermetallic Dy-Dy distance was determined to be 0.756 nm. with a decrease in T, which suggests the existence of an antiferromagnetic (AF) interaction between the Dy 3+ ions. The MH curve for 1 at 1.8 K showed magnetic hysteresis. In ac susceptibility measurements on a powder sample of 1, which were dependent on the applied ac field, indicating that 1 is an single molecule magnet (SMM), a maximum was 22 K at an ac frequency (f) of 1488 Hz. The shape of the peaks drastically changed, and the peaks did not shift when an H dc large enough to suppress the quantum tunneling of the magnetization (Q. TM) was applied. The energy barrier (Δ / hc) was estimated to be 44 cm-1 with a pre-exponential factor (τ0) of 1.6 × 10 -5 s from an Arrhenius plot. Our results suggest that the SMM / magnetic properties of 1 significant change in a dc magnetic field. These relaxation mechanisms are related to the energy gap of the ground state and to QTM.