Influence of Energy Barriers in Triangular Dysprosium Single-Molecule Magnets through Different Substitutions on a Nitrophenolate-Type Coligand.

The effect of the directions of the anisotropy axes on the energy barriers of single-molecule magnets (SMMs) was investigated. By introducing nitrophenolate (NP)-type coligands with different substitutions, the energy barrier was significantly changed. The structural and magnetic properties of three novel SMMs based on trinuclear {Dy3O5} phenoxo- and methoxyl-bridged triangular motifs were explored. All complexes share the formula [Dy3(Hhmb)4(μ3-OMe)2(OMe)(NP)][Dy3(Hhmb)4(μ3-OMe)2(NP)]·solvent·3Cl, where Hhmb = (2-hydroxy-3-methoxyphenyl)methylene(benzoicotino)hydrazine, secondary ligand NP = 2-nitrophenol (2-NP, complex 1), 2,4-dinitrophenol (2,4-DNP, complex 2), and 2,4,6-trinitrophenol (2,4,6-TNP, complex 3), and solvent = 2MeOH·2Et2O (1) and 4MeOH (2 and 3). Magnetic measurements for 1 and 2 revealed observable slow magnetic relaxation behavior with anisotropic energy barriers of 12.18 and 4.96 K, respectively, for SMMs and only the tail of the peaks in the out-of-phase susceptibility, χ″, was observed in complex 3. Comparing a series of NP coligands, we could easily study the correlation between the directions of the anisotropic axes and magnetic properties for this trinuclear SMM system.