Structurally modulated single-ion magnets of mononuclear β-diketone dysprosium(III) complexes.

Five β-diketone based Dy(iii) single-ion magnets (SIMs), [DyIII(TTA)3(AIP)]·0.5CH3CH2OH·0.5H2O (1), [DyIII(TTA)3(APIP)]·2CH3OH·H2O (2), [DyIII(TTA)3(DPP)] (3), [DyIII(TTA)3(BPP)]·0.5CH3CH2OH (4) and [DyIII(TTA)3(AIP)]·1.5H2O (5), were fully synthesized through alteration of their phenanthroline derivates (AIP = 2-(anthracen-9-yl)-1H-imidazo[4,5-f][1,10]phenanthroline, APIP = 2-(4-(anthracen-9-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, DPP = 2,3-diphenylpyrazino[2,3-f][1,10]phenanthroline and BPP = 2,3-bis(2,5-dimethylthiophen-3-yl)pyrazino[2,3-f][1,10]phenanthroline). Magnetic investigations reveal that all the complexes perform as SIMs, with notably different effective barriers of 69.4 K (1), 147.3 K (2), 122.1 K (3) and 234.2 K (4) in zero direct current (dc) field. Complexes of 2 and 4 possess almost twofold higher effective barriers compared to 1 and 3. By analyzing the crystal structures, the distinct magnetic dynamics was found to stem from the variation in intermolecular hydrogen bond interactions and charge delocalization of auxiliary ligands. With the help of ab initio calculations, a change of auxiliary ligand brings about varying intensities of quantum tunnelling magnetization (QTM), which account for the distinguishable magnetic dynamics. With a combination of experimental and theoretical analyses, this work provides a visual and instructive perspective to the understanding of fine tuning auxiliary ligands to design structurally modulated SIMs of mononuclear β-diketone dysprosium(iii) complexes.