Electrical–Magnetic Properties of Solvent-Induced Di- and Hexanuclear Lanthanide Complexes Based on an Unorthodox N-Rich Ligand

We report herein an unusual occurrence of solvent-induced di- and hexanuclear lanthanide (Ln2 and Ln6) complexes using an unorthodox N-rich pyridyl-pyrazole-based ligand. The crystal structures of Ln2 and Ln6 complexes are isostructural and show a common feature: a nonpolar periphery and a polar core where the paramagnetic lanthanide centers are exclusively bridged by oxygen atoms. Such favorable magnetic exchange coupling leads to interesting magnetic behaviors with befitting single-molecule magnet (SMM) and magnetocaloric effect (MCE) features. The Dy2 complex exhibits SMM behavior with befitting frequency and temperature-dependent out-of-phase signals along with an Ueff value of ∼49.3 K and a relaxation time of 4.82 × 10–9 s. Both Gd2 and Gd6 complexes exhibit cryogenic magnetic cooling with a −ΔSM value of 15.2 and 40.6 J kg–1 K–1, respectively, under an applied magnetic field of 5 T at 4 K and 8 T at 2.3 K. Detail theoretical investigations were also performed, which demonstrate gratifying synergism between theoretically derived and the experimentally obtained magnetic properties. The ionic conductivity measurements show excellent ionic conductivity values in the range of 4.32 × 10–4 to 7.92 × 10–4 S/cm at 80 °C and 95% relative humidity.