Regulation of Substituent Effects on Configurations and Magnetic Performances of Mononuclear DyIII Single-Molecule Magnets

A series of mononuclear DyIII compounds, [Dy(tmpd)3(4,4′-dmpy)] (1), [Dy(tffb)3(4,4′-dmpy)] (2), [Dy(tffb)3(5,5′-dmpy)] (3), and [Dy(tmpd)3(5,5′-dmpy)] (4) [tmpd = 4,4,4-trifluoro-1-(4-methoxyphenyl)-1,3-butanedione, tffb = 4,4,4-trifluoro-1-(4-fluorophenyl)-1,3-butanedione, 4,4′-dmpy = 4,4′-dimethyl-2,2′-bipyridyl, and 5,5′-dmpy = 5,5′-dimethyl-2,2′-bipyridyl], have been synthesized by modifying β-diketonate ligands and capping N-donor co-ligands. DyIII ions in 1–4 possess N2O6 octacoordinated environments. Compounds 1 and 2 exhibit distorted trigonal dodecahedron configurations, while 3 and 4 display distorted square antiprismatic configurations. Systematic investigations of the alternating current measurements indicate the different magnetic relaxation dynamics with energy barriers (Ueff) of 66 K (1, 45 cm–1), 189 K, (2, 131 cm–1), 115 K (3, 79 cm–1), and 205 K (4, 142 cm–1). To deeply understand their different magnetic behaviors, the magnetic anisotropies of 1–4 were studied by ab initio calculations...