Zero-field slow magnetic relaxation behavior of Zn 2 Dy in a family of trinuclear near-linear Zn 2 Ln complexes: synthesis, experimental and theoretical investigations.

We hereby report a series of near-linear trinuclear [Zn 2 Ln III (HL) 4 (CH 3 COO)]·(NO 3 ) 2 (where Ln III = La (1-La), Ce (2-Ce), Nd (3-Nd), Sm (4-Sm), Tb (5-Tb), and Dy (6-Dy)) complexes with Schiff base ligand (H2L). Magnetization relaxation dynamic studies on complexes 2-Ce, 5-Tb, and 6-Dy reveal the existence of well resolved frequency dependent zero-field out-of-phase χ '' M signals, which is an indicator of a typical single-ion magnet behavior observed only for complex 6-Dy with U eff = 43.7 K ( τ 0 = 2.42 × 10 -6 s). The presence of two Zn(II) ions near the coordination geometry of Dy(III) ion in 6-Dy is likely to keep the first excited m J levels significantly away from the ground state m J level and is responsible for the observation of zero field slow magnetic relaxation behavior. The data collected in the presence of a magnetic field of H dc = 2 kOe enhances the energy barrier by two-fold (88.63 K, τ 0 = 1.36 × 10 -7 s) in 6-Dy, suggesting the presence of QTM at zero field along with other under barrier relaxations, such as the Raman process. On the other hand, complex 2-Ce shows field induced slow relaxation of magnetization behavior with an effective energy barrier of 12.24 K ( τ 0 = 1.89 × 10 -4 s). The CASSCF/SO-RASSI/SINGLE_ANISO based ab initio calculations using MOLCAS 8.0 code further rationalized our experimentally observed magnetization dynamics.