Luminescent Dy^III single ion magnets with same N₆O₃ donor atoms but different donor atom arrangements, ‘fac’-[Dy^III(HL^DL-ala)₃]·8H₂O and ‘mer’-[Dy^III(HL^DL-phe)₃]·7H₂O

Two Dy^III complexes with same N₆O₃ donor atoms but different donor atom arrangements ‘fac’-[Dy^III(HL^DL-ala)₃]·8H₂O (1) and ‘mer’-[Dy^III(HL^DL-phe)₃]·7H₂O (2) were synthesized, where H₂L^DL-ala and H₂L^DL-phe are tridentate NNO ligands of N-[(imidazol-4-yl)methylidene]-DL-alanine and N-[(imidazol-4-yl)methylidene]-DL-phenylalanine, respectively. Each Dy^III ion is coordinated by three mono-deprotonated mono-negative NNO tridentate ligands to form a nona-coordination geometry of a tricapped trigonal prism (TTP). 1 consists of enantiomers ‘fac’-[Dy^III(HL^D-ala)₃] and ‘fac’-[Dy^III(HL^L-ala)₃], while 2 consists of ‘mer’-[Dy^III(HL^D-phe)₂(HL^L-phe)] and ‘mer’-[Dy^III(HL^D-phe)(HL^L-phe)₂]. The temperature dependence of the magnetic susceptibilities and field-dependence of the magnetization of two complexes showed the different magnetic profiles and the Stark splitting of the ground state ⁶H_15/2 due to the crystal field effect on Dy^III ion (4f⁹, J = 15/2, S = 5/2, L = 5, g_J = 4/3, ⁶H_15/2). Luminescence spectra were observed and the fine structures assigned to the ⁴F_9/2 → ⁶H_15/2 transitions are partially observed. 1 and 2 showed an out-of-phase signal with frequency-dependence in alternating current (ac) susceptibility under a dc bias field of 1000 Oe, indicative of field induced single ion magnet (SIM). The ac magnetic susceptibilities under 1000 Oe dc field of 2 showed the maximum peaks at the higher temperature than those of 1, indicating that the energy barrier of 2 is larger than that of 1.