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Comprehensive Summary: The reaction of DyCl3⋅6H2O with a rigid diacylhydrazone ligand (H2L) afforded a trinuclear precursor [Dy3L2Cl3(H2O)2(CH3OH)]Cl2⋅3CH3OH (1). The replacement of the Cl– ions and the coordinating solvents by the aryloxides ligands (Lx)– yields three trinuclear complexes [Dy3L2(Lx)5]⋅nsol (x = 1,2‐naphthol (2); x = 2,7‐hydroxycoumarin (3); and x = 3, phenol (4)). In complexes 2—4, two end Dy3+ centers adopt almost identical N4O4 coordination sphere of D6h geometry while the central one adopts N4O5 coordination sphere in Cs geometry. Magnetic measurements reveal weak antiferromagnetic interactions in the hydrated samples 2e—4e and two‐step slow relaxation process under zero dc field with effective energy barriers Ueff of 439 and 91 K, 353 and 40 K, 466 and 89 K for SR and FR in 2e—4e, respectively. Such dynamic magnetic behaviour for 4 persists in the magnetically diluted sample of 4@Y. Complex 4 possesses the short Dy‐Oaryloxide bond distance of 2.055(18) Å, and the largest Ueff among the reported linear trinuclear dysprosium complexes. Moreover, the functionalized aryloxides ligands (Lx)– show photoluminescence via intramolecular energy transfer, making 2e—4e luminescent Dy3+ SMMs with high energy barriers. [ABSTRACT FROM AUTHOR]

Two lanthanide single-molecule magnets (SMMs) [Dy3(μ3-OH)(HL-1)3(H2O)3](NO3)2·3H3O (1, H3L-1 = (E)-3-(((8-hydroxyquinolin-2-yl)methylene)amino)propane-1,2-diol) and [Dy6(μ3-OH)4(H2L-2)4(HL-2)2(L-2)2] (2, H3L-2 = (E)-2-hydroxy-N′-(2-hydroxy-3-methoxybenzylidene)benzohydrazide) were synthesized and characterized structurally and magnetically. Complex 1 contains a triangular Dy3 core in which the three Dy3+ ions share a μ3-OH− anion and the deprotonated ligands of (HL-1)2− serve both capping and bridging functions, while 2 displays a centrosymmetric hexanuclear DyIII structure with two similar Dy3 triangular cores ligated by two fully deprotonated (L-2)3− ligands, each of which shares two μ3-OH− anions. All the DyIII ions are eight-coordinated with quasi D2d or C2v symmetry. Magnetic studies reveal that 1 exhibited two-step magnetic relaxation under an applied dc field of 800 Oe, with effective energy barriers of 40.1 and 31.0 K for the slow relaxation (SR) and fast relaxation regimes (FR), respectively. Meanwhile, 2 only showed a tail of slow magnetic relaxation at above 2 K. Ab initio calculations have been carried out to show the nature of their different magnetic properties. [ABSTRACT FROM AUTHOR]

A series of five mononuclear β-diketonate-Dy(III) complexes, with formulas Dy(ntfa)3(Br-bpy) (1), Dy(ntfa)3(Br2-bpy) (2), Dy(ntfa)3(5,5-(CH3)2-bpy) (3), Dy(ntfa)3(4,4-((CH3)3)2-bpy) (4) and Dy(ntfa)3(4,4-(CH3)2-bpy) (5) (ntfa = 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione, Br-bpy = 5-bromo-2,2′-bipyridine, Br2-bpy = 4,4′-dibromo-2,2′-bipyridine, 5,5-(CH3)2-bpy = 5,5′-di-methyl-2,2′-bipyridine, 4,4-((CH3)3)2-bpy = 4,4′-di-tert-butyl-2,2′-bipyridine, and 4,4-(CH3)2-bpy = 4,4′-di-methyl-2,2′-bipyridine), have been prepared by altering the capping N-donor coligands. Dy(III) ions in all complexes possess N2O6 octa-coordinated environments, displaying a distorted square antiprismatic D4d symmetry in complexes 1–4, as well as a triangular dodecahedron D2d symmetry in 5. Magnetic investigations evidence the SIM behavior in the five complexes with the energy barriers (Ueff) of 104.19 K (1), 122.93 K (2), 84.20 K (3), 64.16 K (4) and 80.23 K (5) under zero applied dc field. The potential QTM effects in the title complexes are successfully suppressed in the presence of the extra applied fields. The crystal field parameters and orientations of the magnetic easy axes were obtained from the simulation of the magnetic data and the electrostatic model calculation. The distinct electronic effects originating from the subtle changes of the substituents on the capping N-donor coligands induce varying coordination microenvironments and geometries on the Dy(III) sites, further drastically impacting the overall magnetic properties of the title complexes. The disparities of the uniaxial anisotropy and the magnetic dynamics for 1–5 have been elucidated by ab initio calculations as well. [ABSTRACT FROM AUTHOR]

Four DyIII complexes, [Dy2(NO3)4(L)2(H2O)2]·2MeCN (1), [Dy2(NO3)4(L)2(H2O)2]·2(NO3)·DMBD·2MeOH (2), [Dy2(NO3)4(L)2(TPO)2]·2MeCN (3) and [Dy2(L′)6(H2O)2]·4MeCN (4), were elaborately synthesized, structurally characterized and magnetically investigated (HL = 2,6-dimethoxyphenol, HL′ = 4-hydroxy-3,5-dimethoxybenzaldehyde, DMBD = 1,1′-dimethyl-[4,4′-bipyridine]-1,1′-diium and TPO = phosphine triphenyl oxide). In 1–3, the nearly planar molecular structures consisting of two DyIII ions and two L ligands are almost perpendicular to four nitrate ligands, which provides an opportunity to introduce auxiliary ligands (H2O or TPO) at the terminal position along the Dy⋯Dy orientation of [Dy2]. The slightly discrepant coordination environment around the DyIII ion with different terminal ligands plays a key role in tuning the magnetic anisotropy, and further strongly affects the magnetic properties of 1–4. The magnetic studies reveal that they all behave as single-molecule magnets (SMMs) at zero dc field with ferromagnetic dipole–dipole interaction between DyIII ions. The dynamic magnetic investigations give the energy barriers of 107.5 (1), 127.1 (2), 168.7 (3) and 251.9 K (4), respectively. The magnetic axis orientation of the ground state gradually verges on the Dy–Oaux bond from 1 to 4, leading to the stronger uniaxial anisotropy of DyIII ions and better SMM properties of 3 and 4. In addition, complexes 3 and 4 possess higher energy barriers than reported dinuclear DyIII-SMMs also constructed from HL or HL' with β-diketone. It is believed that the ligands coordinating to the DyIII ion at both terminals of the Dy⋯Dy linkage improve the SMM properties of dinuclear DyIII complexes. This design may provide a new strategy for obtaining dinuclear DyIII-based SMMs. [ABSTRACT FROM AUTHOR]

To explore the influences of magnetic interactions on the relaxation dynamics of single-molecule magnets (SMMs) and to understand the relationship between single-ion relaxation and the relaxation of a molecular entity, it is very important to design dinuclear lanthanide-based SMMs with two-step relaxation processes. Here, three Dy2 complexes of compositions [Dy2(L)2(NO3)2(MeOH)2] (1), [Dy2(L)2(NO3)2(EtOH)2] (2), and [Dy2(L)2(NO3)2(DMF)2]·0.5EtOH (3) (H2L = 2-(((2-hydroxy-3-methoxybenzyl)imino)methyl)-4-methoxyphenol) were successfully synthesized via elaborately introducing different terminal solvent ligands. X-ray single-crystal diffraction analyses revealed that complexes 1–3 are isostructural. The two DyIII ions of 1 and 2 both adopt D2d symmetry, while the two DyIII centres of 3 display D2d and D4d symmetries, respectively. The magnetic property studies of 1–3 indicated that all three complexes exhibit single-molecule magnet (SMM) behaviours with energy barriers of 104 K for 1, 98.94 K for 2, and 76.28 K and 45.54 K for 3 under zero dc field. The target of assembling Dy2 SMMs with two-step relaxation processes was achieved by gradually increasing the sizes of the terminal solvent ligands. Complex 3 exhibits two-step relaxation processes. Complete active space self-consistent field (CASSCF) calculations were performed on 1–3 to rationalize the observed differences in the magnetic behaviour. It is found that both the angles between the magnetic axis and the vector connecting two DyIII ions and the symmetries of DyIII ions are vital factors that affect the energy barriers of 1–3. The high local symmetries of the central metals in 1 and 2 make the complexes act as SMMs with higher energy barriers, while the smaller angle and different symmetries of the two DyIII ions render complex 3 as a SMM with a two-step relaxation process. This work demonstrates a new methodology for preparing SMMs with two-step relaxation processes by fine-tuning the terminal solvent ligands. [ABSTRACT FROM AUTHOR]

The utilization of two Schiff-base ligands H2L1 and H2L2 (H2L1 = 4-chloro-2-(((3-ethoxy-2-hydroxybenzyl)imino)methyl) phenol, H2L2 = 2-(((3-ethoxy-2-hydroxybenzyl)imino)methyl)-4-methoxy-phenol) with different substituents at the backbone of phenol in the construction of dinuclear dysprosium single-molecule magnets (SMMs) is reported. Two complexes of formulae [Dy2(L1)2(NO3)2(EtOH)(DMF)]·2EtOH (1) and [Dy2(L2)2(NO3)2(MeOH)2] (2) have been prepared and structurally characterized. X-ray crystallographic analysis revealed that the four DyIII ions of 1 and 2 all adopt NO7 coordination environments. The two DyIII centers of 1 exhibit triangular dodecahedron (D2d) and square antiprism (D4d) geometries, respectively, while the two DyIII sites in 2 both show triangular dodecahedron geometry with D2d symmetry. Magnetic analyses indicated that both complexes display SMM behavior with energy barriers of 86.91 K (1) and 93.70 K (2), respectively. The slight enhancement of the energy barrier of 2 reveals that the coordination geometries of DyIII ions would affect the magnetic behaviors of 1 and 2. Complete Active Space Self-Consistent Field (CASSCF) calculations were conducted for 1 and 2 to illustrate the slight variation of the magnetic behaviors. The calculated results are well consistent with those of the experimental outcomes. [ABSTRACT FROM AUTHOR]

The reactions of LnIII ions with a versatile pyridyl-decorated dicarboxylic acid ligand lead to the formation of a series of novel three-dimensional (3D) Ln-MOFs, [Ln3(pta)4(Hpta)(H2O)]·xH2O (Ln = Dy (1), Eu (2), Gd (3), Tb (4), H2pta = 2-(4-pyridyl)-terephthalic acid, x = 6 for 1, 2.5 for 2, 1.5 for 3 and 2 for 4). The Ln3+ ions act as nine-coordinated muffin spheres, linking to each other to generate trinuclear {Ln3(OOC)6N2} SBUs, which are further extended to be interesting 3D topological architectures. To the best of our knowledge, the Dy-MOF exhibits zero-field single-molecule magnet (SMM) behaviour with the largest effective energy barrier among the previously reported 3D MOF-based Dy-SMMs. The combined analyses of a diluted sample (1@Y) and ab initio calculations demonstrate that the thermally assisted slow relaxation is mainly attributed to the single-ion magnetism. Furthermore, fluorescence measurements reveal that H2pta can sensitize EuIII and TbIII characteristic luminescence. [ABSTRACT FROM AUTHOR]

The reaction of Dy(NO3)3·6H2O and an asymmetric Schiff-base linker 5-chloro-2-(((2-hydroxy-3-methoxybenzyl)imino)methyl) phenol (H2L) afforded a dinuclear compound [Dy2L2(HL)(NO3)(EtOH)]·0.5C2H5OH (1). Complex 1 features two inequivalent Dy(III) sites, where three ligand sets (one HL− moiety and two L2− groups) are shared by two Dy(III) ions. The strategic introduction of CH3COOH in the reaction system used for synthesizing 1 induces the replacement of the HL− ligand by the CH3COO− ion, consequently resulting in the generation of [Et3NH][Dy2L2(NO3)(CH3COO)2] (2). In complex 2, two Dy(III) centers adopt NO7 (D2d geometry) and NO6 (C2v) coordination sphere, respectively. DC magnetic susceptibility studies for the two complexes indicate ferromagnetic interactions. Complexes 1 and 2 exhibit single-molecule magnet behavior with two-step slow relaxation processes due to the possession of inequivalent metal sites. The energy barriers of 69.19 and 45.73 K for 1, and 92.77 and 72.95 K for 2 are determined. Theoretical calculations reveal that the two-step relaxation processes in both 1 and 2 mainly originate from the single-ion magnetism of two distinct Dy(III) ions with inequivalent coordination environments. [ABSTRACT FROM AUTHOR]

Four tetranuclear 3d–4f complexes, namely [Fe2Ln2(L)2(teaH)2(Cl)2](NO3)2·4CH3CN (H2L = N1,N3-bis(3-methoxysalicylidene)diethylenetriamine, teaH3 = triethanolamine, Ln = Dy for 1 and Ln = Gd for 1′) and [Co2Ln2(L)2(pdm)2(CH3COO)2(CH3OH)2](NO3)2·xCH3OH·yH2O (pdmH2 = 2,6-pyridinedimethanol, Ln = Dy, x = 5 and y = 2.5 for 2 and Ln = Gd, x = 6 and y = 1.5 for 2′), have been reported. Two FeIII and two DyIII in 1 formed a zigzag Fe1–Dy1–Dy1a–Fe1a arrangement with a Fe1–Dy1–Dy1a angle of 105.328(3)°. However, in contrast to 1, two CoIII and two DyIII ions in 2 formed a more linear Co1–Dy1–Dy1a–Co1a arrangement with a Co1–Dy1–Dy1a angle of 141.86(2)°. Additionally, two DyIII ions in 1 are eight-coordinated with a triangular dodecahedron geometry, while two DyIII ions in 2 adopt nine-coordination with a muffin geometry. Magnetic studies revealed slow magnetic relaxation behavior for 1, with an energy barrier Ea of 6.9 K. For 2, single molecule magnet behavior was presented under a zero dc field with an effective energy barrier Ueff of 64.0(9) K. Ab initio calculations for 1 and 2 indicate that compared to 2, complex 1 has a larger transversal magnetic moment of its ground Kramers doublets (KD) and a larger value of the tunnelling parameter (Δt) for the exchanged coupled ground state, which may result in poor single molecule magnet behavior for 1. [ABSTRACT FROM AUTHOR]