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Three mononuclear Dy III complexes with the same auxiliary ligand Lz (2,4-diamino-6-pyridyl-1,3,5-triazine), [Dy(TTA) 3 Lz] (1Dy) (TTA = 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionate), [Dy(acac) 3 Lz]·CH 3 OH·0.5H 2 O (2Dy) (acac = acetylacetonate), and [Dy(MQ) 2 Lz 2 ]Br·CH 3 OH (3Dy) (HMQ = 2-methyl-8-quinolinol), have been synthesized through alteration of the ligands containing O donors. In all three complexes, the Dy III ions are eight-coordinate and submitted to pseudo- D 4 d symmetry in the first coordination sphere. It is noteworthy that the TTA ligands in 1Dy are easily substituted by other bidentate capping ligands with O donors, leading to distinct magnetic properties, which were studied experimentally and via ab initio calculations. All three complexes were found to exhibit single-molecule magnet behavior with U eff of 22 cm -1 (1Dy), 112 cm -1 (2Dy), and 56 cm -1 (3Dy) under zero applied dc field. Complex 1Dy demonstrates inferior SIM properties compared with 2Dy and 3Dy, which can be attributed to the strong electron-withdrawing effects of TTA ligands, as confirmed by theoretical calculations. However, butterfly-shaped magnetic hysteresis in 1Dy and 3Dy was observed at 1.9 K, while not in 2Dy.

A series of mononuclear Dy III complexes with the general formula [DyLz 2 (salicylaldehyde) 2 ]·X·solvent (Lz = 6-pyridin-2-yl[1,3,5]triazine-2,4-diamine; X = OH - (1·OH), Cl - (2·Cl), Br - (3·Br)) have been synthesized using mixed salicylaldehyde/pyridinyl-triazine ligands and discriminative counteranions. The Dy III ion in these three complexes resides in a similar D 4d coordination geometry with counteranions perturbing the coordination environment and bond lengths and angles in the lattice. Magnetostructural studies reveal that the asymmetric distribution of salicylaldehyde/pyridinyl-triazine ligands and the presence of discriminative counteranions result in the coexistence of large anisotropy and quantum tunneling of magnetization. The magnetic anisotropy is dominated by the axial ligand field with short Dy-O sali distances and large ∠O sali -Dy-O sali angles, while the quantum tunneling relaxation is probably dictated by the π-π stacking of the Lz ligands, which induces an axial constriction of the coordinating plane. Ab initio calculations substantiate the diversity of the magnetic behaviors in these complexes and highlight the importance of axial ligand field with short Dy-O sali distances, large ∠O sali -Dy-O sali angles and less ligand stacking in these pseudo-D 4d -symmetrical single-molecule magnets.

A series 1.Ln of tetranuclear lanthanide clusters [Ln 4 (μ 4 -O)L 2 (PhCOO) 6 ]·solvent (Ln = Gd (1.Gd), Dy (1.Dy), Ho (1.Ho)) and octanuclear lanthanide Ln 4 cluster pairs 2.Ln [Ln 8 (μ 3 -OH) 4 (CO 3 ) 2 L 4 (PhCOO) 8 ]·solvent (Ln = Gd (2.Gd), Dy (2.Dy), Tb (2.Tb)) were assembled by using a bi-Schiff-based ligand H 2 L and characterized structurally and magnetically. Interestingly, the octanuclear Ln 4 cluster pairs 2.Ln are proposed to be assembled from the tetranuclear clusters 1.Ln through the uptake of CO 2 from air in a more basic media. X-ray structural analyses approved the possible evolution mechanism. Magnetic studies reveal the coexistence of ferro- and anti-ferromagnetic interaction in 1.Gd and 2.Gd by simulating the direct-current magnetic susceptibility and indicate the CO 3 2- bridges produce weak ferromagnetic interaction in 2.Gd rather than anti-ferromagnetic interaction by benzoate bridges in 1.Gd. The magnitude of the magnetocaloric effect has been examined and shows that complex 2.Gd exhibits larger magnetocaloric effect than 1.Gd, which could be probably ascribed to the weak ferromagnetic interaction produced by the CO 3 2- bridges.