Magnetic relaxation behavior of a spatially closed dysprosium(III) phthalocyaninato double-decker complex

Abstract

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. χMT versus T plots for 1 decreased with a decrease in T, which suggests the existence of an antiferromagnetic (AF) interaction between the Dy3+ 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 Hdc large enough to suppress the quantum tunneling of the magnetization (QTM) 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 significantly change in a dc magnetic field. These relaxation mechanisms are related to the energy gap of the ground state and to QTM.