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 [{Nd(bbpen)(HO)}Cl] 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 HO 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) 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.