Effect of Substituents in Equatorial Hexaazamacrocyclic Schiff Base Ligands on the Construction and Magnetism of Pseudo Single-Ion Magnets.

Three mononuclear Dy compounds [DyL(PhSiO)][BPh]·MeCN·2HO (), [DyL(PhSiO)][BPh]·CHOH·HO (), and [DyL(PhSiO)(OAc)][BPh]·CHOH·3HO () and their corresponding Y diluted analogues [DyYL(PhSiO)][BPh]·MeCN·2HO (), [DyYL(PhSiO)][BPh]·CHOH·HO (), and [DyYL(PhSiO)(OAc)][BPh]·CHOH·3HO () were synthesized with hexaazamacrocyclic Schiff base ligands as an equatorial ligand. The substituents in the equatorial hexaazamacrocyclic Schiff base ligand show a significant effect on the replacement of the axial ligands. Compounds , , and are typical zero dc field single-molecule magnets with effective energy barriers () of 1092(6), 946.1(7), and 150.1(9) K, respectively. Although the effective energy barriers of and are close, the magnetic hysteresis remains open up to 20 K for , twice as large as that of (10 K), which is different from the previously reported compounds, probably due to nonplanarity N6 in the equator. calculations indicate that the ground states of compounds and exhibit high anisotropy and pure second and third excited states, while compound exhibits pure ground-state anisotropy and highly mixed excited states, leading to the easy occurrence of quantum tunneling of magnetization between the ground and excited states in compound . This work indicates that the substituents in equatorial hexaazamacrocyclic Schiff base ligands have a significant effect on the construction and magnetic properties of Dy SIMs with D symmetry.