Pentagonal Bipyramidal Dy(III) Ions Bridged by Homologous Metallocyanate Anions into One-Dimensional Chain Structures Exhibiting Distinct Magnetic Relaxation Properties

The continuously growing axially compressed pentagonal bipyramidal DyIII mononuclear structures exhibit excellent SIM properties. However, it is quite challenging to assemble these mononuclear fragments into a magnetic coupling system. Here we report a family of one-dimensional chain compounds, 1YFe, 2DyCr, 3DyFe, 4DyFe0.05Co0.95, and 5DyCo, composed of pentagonal bipyramidal rare earth (REIII) fragments bridged by homologous metallocyanate anions TM(CN)63- (TMIII = CrIII, FeIIILS, CoIII). Their similar chain structure is beneficial to compare the influence of intrachain DyIII···TMIII magnetic interactions on the DyIII SIMs performance and study the possible exchange-based SCM relaxation behavior. The hysteresis loops of 2DyCr-5DyCo widen sequentially at each of the same temperatures. Meanwhile, 2DyCr-5DyCo exhibits increasingly strong frequency-dependent AC magnetic susceptibilities and progressively decreasing QTM effect (HDC = 0 Oe). This indicates that the intrachain DyIII···TMIII magnetic interactions mainly act as a transverse field on the DyIII single-ion relaxation, and as the magnetic interaction strengthens, the QTM process accelerates. After applying an external field, 2DyCr and 3DyFe exhibit a coexistence of dual relaxation processes, suppressing the QTM effect. Ab initio calculations suggest that these processes correspond to the slow relaxation of DyIII single ions and the fast relaxation of the intrachain DyIII···TMIII (CrIII or FeIIILS) exchange-based SCM behavior, respectively.