Slow Magnetic Relaxation with High Energy Barrier in Kramer Nd (III) Dinuclear Complex

A dinuclear Nd(III) complex was synthesized and characterized via single-crystal X-ray diffraction and magnetic measurements. The crystal structure of [{Nd₂(bbpen)₂(H₂O)₂}Cl₂] reveals the presence of symmetrically similar but crystallographically different two Nd(III) ions. In the dinuclear unit, phenoxide-bridged Nd(III) ions remain in distorted square antiprismatic (SAP) geometry. The anti-orientation of coordinated H₂O makes intra-molecular hydrogen bonding with the axial phenoxide moiety. The presence of two external Cl⁻ ions neutralized the charge of the dimeric unit. The AC magnetic properties of the complex showed field-induced single-molecule magnetic behavior. The dynamic magnetic relaxation was fitted using linear as well as nonlinear equations. The high-temperature linear fitting gives a thermal energy barrier of about 32 K, whereas fitting the entire temperature range with Orbach and quantum tunnelling of magnetization (QTM) relaxation processes provides a phenomenological energy barrier of 37 K. The energy barrier (U_eff) of this Nd(III) complex is not only the highest for dinuclear Nd(III) single-molecule magnets (SMMs) but also one of the highest for polynuclear Nd(III)-based SMMs to date. The ab initio calculation further corroborated the experimentally obtained magnetization dynamics.