Single-Ion Magnetism in a Three-Dimensional Thiocyanate-Bridged Dysprosium(III) Framework

New three-dimensional (3D) lanthanide framework compounds supported by bridging thiocyanate ligand and K+ cations, K-4[Ln(NCS)(4)(H2O)(4)](NCS)(3)(H2O)(2)(1: Ln = Dy, 2: Ln = Tb, 3: Ln = Gd) have been synthesized. A single-crystal X-ray diffraction study showed that all three compounds were isostructural and crystallized in the I 2/a space group. The K+ ion form 2D layers with thiocyanates which are further linked by [Ln(NCS)(4)(H2O)(4)](-) complexes and additional thiocyanate ions to generate an interesting 3D framework structure. Compound 1 shows slow magnetic relaxation behavior under a zero direct current (DC) field, indicating that 1 behaves as a single-ion magnet (SIM). As estimated from AC magnetic measurements, the effective energy barrier for spin reversal in 1 was U-eff = 42 cm(-1). Slow relaxation of magnetization under a small external DC field was also detected for 2 and 3 at 1.8 K.