Influence of lattice water molecules on the magnetization dynamics of binuclear dysprosium(III) compounds: insights from magnetic and ab initio calculations.

Lattice water effects on the structures and magnetic properties of single-molecule magnets (SMMs) have attracted considerable attention. Herein, we have successfully synthesized two centrosymmetric binuclear compounds [Dy2(2,3'-ppcad)2(C2H3O2)4(H2O)2] (1) and [Dy2(2,3'-ppcad)2(C2H3O2)4(H2O)2]·6H2O (2) (2,3'-Hppcad = N3-(2-pyrazinyl)-3-pyridinecarboxamidrazone) by elaborately varying the amount of the base (LiOH·H2O). Through isothermal titration calorimetry (ITC), the interactions between DyIII ions and 2,3'-Hppcad with different amounts of LiOH·H2O were monitored in real time. Magnetic studies reveal that two compounds exhibit the typical zero-field single-molecule magnet behavior with different energy barrier (Ueff) values of 103.43 K for 1 and 386.48 K for 2, wherein the SMM performance for 2 stands out among the reported nine-coordinated Dy2-SMMs systems with spherical capped square antiprism (C4v) geometries. To rationalize the observed difference in the magnetic properties of 1 and 2, ab initio calculations have been performed. The introduction of lattice water molecules leads to differences in the J values observed for 1 and 2. The stronger antiferromagnetic DyIII-DyIII couplings in 2 were presented and the fast quantum tunneling of magnetization was further suppressed, thereby achieving a higher Ueff value. This work provides an effective strategy to enhance the SMM performance, and combines with ab initio calculations to explain how lattice water molecules can affect the magnetic interactions of Dy2-SMMs.

High temperature quantum tunnelling of magnetization and thousand kelvin anisotropy barrier in a Dy2 single-molecule magnet.

We report here a dinuclear DyIII iodine-bridged single-molecule magnet self-assembled by cis/trans coordination chemistry that displays a large anisotropy barrier of ca. 1300 K and a hysteresis opening temperature of 16 K. High temperature quantum tunnelling of magnetization is observed up to 56 K in zero-field and explained by the combination of the large anisotropy barrier and the local transverse field at the trans site. The results provide a model for thorough understanding of the effect of electronic structure on the magnetic behavior of lanthanide complexes.

Synergistic effect of mixed ligands on the anisotropy axis of two dinuclear dysprosium complexes.

We present the syntheses, crystal structures, magnetic properties and theoretical calculations performed on two dinuclear dysprosium complexes with formulas Dy2(L1)2(L2)2(CH3CH2OH)(CH3OH) (1) and Dy2(L1)2(L3)2(CH3OH)2·1.5CH3OH (2). Single-crystal X-ray structural data analyses showed that both complexes contain two nonequivalent dysprosium ions bridged by two phenolate oxygen atoms. In both complexes, each dysprosium site adopts a N2O6 coordination constitution and triangular dodecahedron (D2d) configuration geometry with different distortion degree. Both complexes display single-molecule magnet behavior manifested by frequency-dependent out-of-phase alternating current susceptibility signal peaks under a zero-applied dc field. The effective energy barrier of the magnetization reversal and relaxation time values are 61 K, 7.1 × 10-6 s (1) and 51 K, 1.9 × 10-6 s (2), respectively. Theoretical calculations revealed a drastic discrepancy between the orientations of the anisotropy axis of the Dy2 ion observed in these two dinuclear complexes, resulting from the different spatial arrangements of the mixed ligands in the core structure.

An Inconspicuous Six-Coordinate Neutral DyIII Single-Ion Magnet with Remarkable Magnetic Anisotropy and Stability.

It is a crucial challenge to address both magnetic anisotropy and stability for single-molecule magnets (SMMs) used in next-generation nanodevices. Highly axial lanthanide SMMs with neutral charge and moderate coordination numbers represent promising magnetic materials. Here, using iodide ions with large volume and low surface charge density as weak donors, we report a six-coordinate neutral dysprosium SMM [Dy(Cy3PO)2I3(CH3CN)] with a certain degree of stability exhibiting a huge thermal barrier of 1062 K and hysteresis loops open up to 9 K. Through the elaborate reduction of ligand field strength, an apparent strongly axial crystal field is provided which elicits prominent crystal-field splitting and high axiality with the thermally activated relaxation via the third-excited Kramers' doublet. Moreover, the profound influence of strong equatorial ligand substitution on the electronic structure and relaxation pathway is clearly explored in DyIII analogues. The result suggests the great potential of the reducing the transverse ligand field in the improvement of SMMs performance.

A Trinuclear Zinc Coordination Cluster Exhibiting Fluorescence, Colorimetric Sensitivity, and Recycling of Silver Ion and Detection of Cupric Ion.

The detection and reusage of transition-metal ions play a crucial role in human health and environmental protection. Recently, various analytical methods and substances have been successfully applied to probe or sense silver ions; however, rare representative examples have been presented regarding the simultaneous detection of silver and silver recycling with the elemental silver powder form. Herein, an unparalleled sensing mechanism for silver ions and recycling silver in its elemental form is exemplified by a fluorescent trinuclear zinc coordination cluster possessing the dual function of colorimetric sensing of silver and responding cupric ions. A Schiff-base-based trinuclear zinc coordination cluster, 1, with formula Zn3(L1)2(CH3COO)2(H2O)2, has been successfully synthesized by the initial exploration of multidentate ligand H2L1-((E)-2,4-di-tert-butyl-6-((2-hydroxy-3-methoxybenzy-lidene)amino)phenol) with various metal ions under self-assembly reactions. Complex 1 is highly fluorescent in solution and as a solid, in addition to acting as a fluorescence sensor toward AgI in ethanol media. Compound 1 displays distinctive sensing of AgI through the fluorescence quenching effect at 576 nm and signal augment at 446 nm over 11 kinds of cations in the absence of interference. The proposed sensing mechanism is attributed to the ligands in 1 which interact with AgI; the ligands undergo oxidation cyclization reaction, leading to the formation of 2 with the formula Zn3(L2)4(CH3COO)2·2CH3CH2OH·H2O, and AgI reduction to elemental Ag powder. Compound 1 presents specific selectivity and sensitivity for AgI in ethanolic solution with a detection limit of 0.1722 µM. The orange color of 1 changes to colorless during the mixing of a small amount of AgI, revealing its potential practical application in naked-eye detection of AgI. Furthermore, 2 exhibits obvious fluorescence emission at 448 nm (λex = 380 nm) and selectively responds to CuII over 11 kinds of metal ions with the fluorescence "turn-off" owing to the formation of 3 in ethanolic solution; it also has a detection limit of 0.0226 µM.

Bromine-bridged Dy2 single-molecule magnet: magnetic anisotropy driven by cis/trans stereoisomers.

We report the first bromine-bridged dinuclear [Dy(Cy3PO)2(µ-Br)(Br)2]2·2C7H8 single-molecule magnet with an effective energy barrier of 684 K and magnetic hysteresis below 3 K. The asymmetric DyIII centres present two unique stereoisomeric octahedral coordination environments depending on the cis/trans disposition of the Cy3PO ligands, leading to the orthogonality of the easy magnetic axes that annihilates the dipolar interactions.

Fine-tuning the type of equatorial donor atom in pentagonal bipyramidal Dy(iii) complexes to enhance single-molecule magnet properties.

A family of new structurally manipulable pentagonal-bipyramidal (PBP) DyIII SMMs, with formulas [Dy(Hbpen)(Cl)3] (1), [Dy(Hbpen)Cl(OPhBr2NO2)2] (2), [Dy(Hbpen)(OPhCl2NO2)3] (3) and [Dy(Mbpen)(Cl)3] (1CH3), were controllably prepared based on a H-substituted amine-based ligand N,N'-bis(2-pyridylmethyl)-ethylenediamine (Hbpen) or a CH3-substituted amine-based ligand N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)-ethylenediamine (Mbpen) and are compared with the reported imine-based DyIII analogues (1'-3'). Upon fine-modulating the type of nitrogen donor on the pentagon plane, the electronic effect is efficiently implemented to significantly modify the magnetic anisotropy and SMM behavior of PBP complexes. Notably, the amine-based 2 shows a three-fold improved energy barrier and an observable hysteresis opening up to 3 K. 1 and 1CH3 exhibit slower relaxation and enhanced anisotropy compared to the imine-based analogue, accompanied by the reorientation of magnetic easy axes. Conversely, poor magnetic properties are observed in 3 after the reduction of imine. The changes in SMM behavior and uniaxial anisotropies are rationalized by both experimental and theoretical studies. The H-substituted amine has formally a larger magnitude of negative charge than imine due to the polarized N-H σ bond. However the repulsion generated by the sp3 N of amine towards the DyIII ion is also affected by the orientation of lone pair electrons. The present work provides a feasible way to rationally optimize the SMM performance of DyIII complexes, highlighting the importance of the electronic properties of an equatorial donor in controlling the quantum tunneling and the magnetic relaxation of PBP DyIII-SMMs.

Effect of coordination anion substitutions on relaxation dynamics of defect dicubane Zn2Dy2 tetranuclear clusters.

We showcase the coordination anion substitution effect on the relaxation dynamics of defect dicubane Zn2Dy2 tetranuclear clusters. On utilization of the coordination similarity of acetate and nitrate anions, we successfully isolated two defect dicubane Zn2Dy2 tetranuclear clusters with formulas [Zn2Dy2(L)4(NO3)2(CH3OH)2]·2CH3COCH3 (1) and [Zn2Dy2(L)4(CH3COO)2(CH3CH2OH)2]·4CH3COCH3 (2), where L denotes the fully deprotonated H2L ligand (E)-4-(tert-butyl)-2-((2-hydroxy-3-methoxybenzylidene)amino)phenol. Such a subtle change in the coordination anion around the DyIII site imposes a significant effect on the distinct relaxation dynamics in 1 and 2. Their magnetic properties were characterized through SQUID magnetometry and theoretical calculations to determine the effective energy barrier, energy levels, magnetic anisotropy and intracluster magnetic exchange coupling interactions. Both tetramers display frequency dependence of the out-of-phase ac magnetic susceptibility signal under zero applied dc field associated with single-molecule magnetic behaviour. The effective energy barriers of 1 and 2 are 108 and 40 cm-1, respectively. Theoretical calculations suggest that the different relaxation dynamics between them are mainly ascribed to the variation of the coordination anion around the DyIII site.

Solvent-tuned magnetic exchange interactions in Dy2 systems ligated by a µ-phenolato heptadentate Schiff base.

A series of binuclear dysprosium compounds, namely, [Dy(api)]2 (1), [Dy(api)]2·2CH2Cl2 (2), [Dy(Clapi)]2·2C4H8O (3), and [Dy(Clapi)]2·2C3H6O (4) (H3api = 2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazoline; H3Clapi = 2-(2'-hydroxy-5'-chlorophenyl)-1,3-bis[3'-aza-4'-(2''-hydroxy-5''-chlorophenyl)prop-4'-en-1'-yl]-1,3-imidazolidine), have been isolated by the reactions of salen-type ligands H3api/H3Clapi with DyCl3·6H2O in different solvent systems. Structural analysis reveals that each salen-type ligand provides a heptadentate coordination pocket (N4O3) to encapsulate a DyIII ion and all of the DyIII centers in 1-4 adopt a distorted square antiprism geometry with D 4d symmetry. Magnetic studies showed that compound 1 did not exhibit single-molecule magnetic (SMMs) behavior. With the introduction of different lattice solvents, compounds 2-4 showed filed-induced slow magnetic relaxation with barriers U eff of 18.2 K (2), 28.0 K (3) and 16.4 K (4), respectively. Ab initio calculations were employed to interpret the magnetization behavior of 1-4. The combination of experimental and theoretical data reveal the importance of the weak exchange interaction between the DyIII ions in the observation of slow magnetic relaxation, and a relaxation mechanism has been developed to rationalize the observed difference in the U eff values. The different lattice solvents influence Dy-O-Dy bond angles and thus alter the torsion of the square antiprism geometry, consequently resulting in distinct magnetic interactions and the magnetic behavior.

Influence of alcoholic solvent and acetate anion coordination mode variations on structures and magnetic properties of heterometallic Zn2Dy2 tetranuclear clusters.

The present work clarifies how slight modifications of the synthetic conditions (e.g., employment of different alcoholic solvents) can result in the variation of the coordination mode of an acetate anion yielding two structurally similar heterometallic Zn2Dy2 tetranuclear clusters with formulas [Zn2Dy2(L)4(CH3COO)2(CH3CH2OH)2]·2CH2Cl2·0.5H2O (1) and [Zn2Dy2(L)4(CH3COO)2(CH3OH)2]·4CH2Cl2·2CH3OH·0.1H2O (2), where H2L is (E)-4-(tert-butyl)-2-((2-hydroxy-3-methoxybenzylidene)amino)phenol. Complexes 1 and 2 were synthesized by varying the alcoholic solvent employed in the synthesis. The ethanol solvent in 1 led to the acetate anion being coordinated to the DyIII ion in bidentate chelating mode while the methanol solvent in 2 generated the acetate anion coordinated to the DyIII ion in bridging mode. Such a subtle change of the coordination mode of the acetate anion on the DyIII ion imposes a significant effect on the distinct dynamic relaxation in 1 and 2. The magnetic properties of 1 and 2 were characterized through SQUID magnetometry and theoretical calculations to determine the effective energy barrier, energy levels, magnetic anisotropy and intracluster magnetic exchange coupling parameters. Both tetramers show frequency dependence of the out-of-phase ac magnetic susceptibility signal under zero applied dc field associated with single-molecule magnetic behaviour. The effective energy barriers of 1 and 2 are 115.4 and 104.2 cm-1, respectively. Theoretical calculations suggest that the different magnetic behaviours between 1 and 2 are mainly due to the coordination mode variations of the acetate anion on the DyIII site. The present result highlights how a subtle modification in the reaction alcoholic solvent resulted in two structurally similar tetranuclear Zn2Dy2 examples with different magnetic behaviours.

Two {ZnDyIII} complexes supported by monophenoxido/dicarboxylate bridges with multiple relaxation processes: carboxylato ancillary ligand-controlled magnetic anisotropy in square antiprismatic DyIII species.

Two linear-shaped heterometallic trinuclear {ZnII2DyIII} clusters were prepared with a compartmental Schiff-base ligand and carboxylate as the co-ligand. The central DyIII ion is sandwiched by two [ZnHhms(RCOO)2] (H2hms = (2-hydroxy-3-methoxybenzylidene)-semicarbazide) units to form a distorted square antiprismatic (SAP) geometry with D4d symmetry. The DyIII and ZnII ions are triply bridged by one unique monophenoxido/dicarboxylate group, where one of the carboxylates shows a severe angular distortion. The magnetic analysis revealed a field-dependent change with two relaxation processes in 1 and 2, which originated from the molecular magnetic center and dipolar-dipolar coupling. The dipole-induced slow relaxation disappeared upon magnetic-site dilution, while another faster relaxation appeared in the high frequency region associated with the different distortions of the antiprismatic sites for 1 and disordered structures for 2. Ab initio calculations revealed that two {ZnII2DyIII}-carboxylate complexes are axial in nature, but the remarkable quantum tunnelling of the magnetization exists in the ground state, which lowers the anisotropic barrier and prohibits zero-field single-molecule magnet behavior. The crystal field of the carboxylato ancillary ligands produces a competitive effect with the phenoxido bridging ligands on the magnetic anisotropy of the lanthanide ions, which greatly affects the electrostatic distribution of this type of {ZnII2DyIII} single-ion magnets (SIMs). The results offer a model for further investigating structural factors in the relaxation mechanism of SIM systems.

Experimental and Theoretical Interpretation on the Magnetic Behavior in a Series of Pentagonal-Bipyramidal DyIII Single-Ion Magnets.

Taking advantage of the steric hindrance and charge-driving effects, four air-stable pentagonal bipyramidal mononuclear DyIII compounds were hydrothermally synthesized. With a tetradentate ligand, N,N'-bis(2-methylenepyridinyl)ethylenediamine (Bpen), invariably coordinates to DyIII in an equatorial plan, 1-3 achieve an orderly transformation of the ligand field by sequentially replacing the remaining sites of the DyIII ion. Compound 4 possesses the same coordination atoms but a different peripheral coordination sphere with 3. Magnetic characterizations display that the compounds are field-induced single-ion magnets (SIM) with actually low barriers, even though 2 has both the same atoms and a similar geometry of the first sphere compared with [Dy(bbpen)Cl] (2', H2 bbpen=N,N'-bis(2-hydroxybenzyl)-N,N'-bis(2-methylpyridyl)ethylenediamin), a high-performance SIM previously reported. Detailed ab initio calculations have been employed to further elucidate the electronic and magnetic structure of the low-lying energy levels of compounds 1-4 and 2'. The theoretical results indicate there is an apparent difference in the electronic structure for these compounds. The analysis on the electrostatic potential further demonstrates that although the pentagonal bipyramidal D5h is one of the ideal configurations expected, the electron density of the donor atoms from the different hybridizations and other functional groups, outside the first sphere, should also be considered in the rational design of promising molecular magnets.

Magnetic Interaction Affecting the Zero-Field Single-Molecule Magnet Behaviors in Isomorphic {NiII2DyIII2} and {CoII2DyIII2} Tetranuclear Complexes.

Great interest is being shown in investigating magnetic interactions that efficiently influence lanthanide single-molecule magnet behavior. A series of heterometallic complexes [M2Ln2(Hhms)2(CH3COO)6(CH3OH)2(H2O)2]·(NO3)2 (M = NiII, Ln = DyIII (1), GdIII (2), and YIII (3); M = CoII, Ln = DyIII (4), GdIII (5), and YIII (6)) have been prepared with a compartmental Schiff-base ligand, 1-(2-hydroxy-3-methoxybenzylidene)-semicarbazide (H2hms), featuring a zigzag-shaped MII-LnIII-LnIII-MII metallic core arrangement. In complexes 1-6, a unique monophenoxo/diacetate asymmetric bridging connects MII ion with LnIII ion, and four acetates bridge two LnIII ions where acetates play essential roles as coligand in generating the tetranuclear units. Magnetic studies reveal the presence of predominant ferromagnetic coupling in DyIII and GdIII derivatives, and slow relaxation of magnetization is observed for {Ni2IIDy2III} and {CoII2DyIII2} with an energy barrier of 16.0 K for {Ni2IIDy2III} and 6.7 K for {CoII2DyIII2} under zero static field. Compared with the analogue {CoII2DyIII2}, the {Ni2IIDy2III} shows longer relaxation time and an absence of the quantum tunnelling of the magnetization (QTM) at low temperatures. Ab initio calculations suggest that the zero-field QTM of {Ni2IIDy2III} is effectively interrupted thanks to the ferromagnetic exchange coupling generated between NiII and DyIII ions. The presence of ferromagnetic exchange between NiII and DyIII ions is more conducive to zero-field single-molecule magnet behaviors than in isomorphic {CoII2DyIII2} where the exchange is antiferromagnetic.

Unusual undecanuclear heterobimetallic Zn4Ln7 (Ln = Gd, Dy) nano-sized clusters encapsulating two peroxide anions through spontaneous intake of dioxygen.

The synthesis, characterization and properties of two unprecedented undecanuclear heterobimetallic Zn4Ln7 complexes of formula [Zn4Ln7(L)8(O2)2(OH)4(Cl)4(H2O)4]·Cl·4H2O·4CH3CN (Ln = Gd (1), Dy (2)) encapsulating two peroxide anions are presented, representing a very rare example of a 3d-peroxo-Ln system and expanding the realm of metal-peroxo complexes. These eleven metal ions are arranged in a peculiar structural motif, where Zn4 is located at the peripheral shell wrapping Ln7 in the inner core. The Zn ions are penta-coordinate in all cases, linked to the NO2 donor atoms from the L2- ligand and to a hydroxyl group, and the apical position is occupied by a chloride anion. All LnIII ions in these systems are octa-coordinate with LnO8 and LnNO7 coordination spheres. Magnetocaloric effect (MCE) behavior has been found in the Gd analogue due to multiple low lying excited states arising from antiferromagnetic Gd-Gd exchange interactions. The Dy derivative shows frequency dependent out-of-phase signals indicating the presence of slow relaxation of magnetization below 8 K under zero applied direct current (dc) field, but without reaching a maximum, which is due to a faster quantum tunneling relaxation. The effective barrier extracted from the frequency dependent data is Ueff = 11.2 K and a τ0 of 4.18 × 10-6 s.

Low temperature heat capacity, standard entropy, standard enthalpy and magnetic property: a new 1D CuII coordination polymer incorporating tetrazole-1-acetic acid and p-nitrobenzoic acid.

A new 1D CuII coordination polymer, formulated as {[Cu(TZA)(PNA)]·H2O}n (1) (HTZA = tetrazole-1-acetic acid, HPNA = p-nitrobenzoic acid), was synthesized and structurally characterized. Thermogravimetric analysis demonstrated that the main frame of 1 exhibited good thermostability up to 473 K. The non-isothermal kinetics for the first exothermic process of 1 were studied by Kissinger and Ozawa methods. The magnetic study revealed that 1 possessed antiferromagnetic exchange interactions between CuII ions through the carboxyl-bridge. The low-temperature (1.9 to 300 K) heat capacity of 1 was measured using the heat-capacity option of a Quantum Design Physical Property Measurement System (PPMS). In addition, the thermodynamic functions in the experimental temperature range were derived by fitting the heat-capacity data to a series of theoretical and empirical models. The standard entropy and standard enthalpy of 1 were respectively calculated to be 411.37 ± 4.11 J mol-1 K-1 and 60.21 ± 0.60 kJ mol-1.

Magnetization Dynamics Changes of Dysprosium(III) Single-Ion Magnets Associated with Guest Molecules.

Two Dy(III) single-ion magnets with a trigonal dodecahedron (D2d) for 1 and an approximately square-antiprismatic (SAP, D4d) N2O6 coordination environment for 2, formulated as [Dy(Phen)(tfmb)3] (1) and [Dy(Phen)(tfmb)3]·0.5(1,4-dioxane) (2) (tfmb = 4,4,4-trifluoro-1-(4-methylphenyl)-1,3-butanedione, Phen = 1,10-phenanthroline), were obtained. Therein, complex 1 was transformed to 2 in 1,4-dioxane solution. Structural analysis shows that complexes 1 and 2 have differing local symmetry of Dy(III) ions. Magnetic studies indicate that the barrier heights (ΔE/kB) of 1 and 2 are 63.56 and 102.82 K under zero dc field as well as 118.50 and 164.55 K under 1200 Oe dc field, respectively. Based on the frequency dependencies of the ac susceptibilities, the effective barriers (ΔE/kB) and the pre-exponential factors (τ0) are 67.05 K and 4.57 × 10(-6) s for 1 and 95.88 K and 2.39 × 10(-7) s for 2 under zero dc field. The present work illustrates that guest-determined notable structure change results in different barrier heights.

Dysprosium(III) complexes with a square-antiprism configuration featuring mononuclear single-molecule magnetic behaviours based on different ß-diketonate ligands and auxiliary ligands.

Three mononuclear dysprosium(III) complexes derived from three ß-diketonate ligands, 4,4,4-trifluoro-1-(4-methylphenyl)-1,3-butanedione (tfmb), 4,4,4-trifluoro-1-(4-fluorophenyl)-1,3-butanedione (tffb) and 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione (tfnb) as well as auxiliary ligands, 5-nitro-1,10-phenanthroline (5-NO2-Phen), DMF and 2,2'-bipyridine (bpy) have been synthesized and structurally characterized, namely [Dy(5-NO2-Phen)(tfmb)3] (1), [Dy(DMF)2(tffb)3] (2) and [Dy(bpy)2(tfnb)3]·0.5(1,4-dioxane) (3). The metal ions in 1-3 adopt an approximately square-antiprismatic (SAP) coordination environment with D4d axial symmetry. The magnetic properties of 1-3 have been investigated, displaying weak out-of-phase AC signals under a zero-DC field. With an applied DC field of 1200 Oe, the quantum tunnelling of the magnetization was suppressed in 1-3 with the pre-exponential factor τ0 = 5.3 × 10(-7) s and the effective barrier ΔE/kB = 83 K for 1 as well as the pre-exponential factor τ0 = 3.09 × 10(-7) s and the effective barrier ΔE/kB = 39 K for 3. Interestingly, for the frequency dependence of the out-of-phase (χ'') of the AC susceptibility of 2, two slow relaxation of the magnetization processes occurred under the applied magnetic field of 1200 Oe, corresponding to the fast relaxation (FR) phase and slow relaxation (SR) phase, respectively. Arrhenius analysis gave the effective energy barrier (ΔE/kB) of 55 K and the pre-exponential factor (τ0) of 8.23 × 10(-12) for the SR. It is thus very likely that the FR process in complex 2 results from QTM enhanced by dipolar interactions between the Dy ions or the presence of the applied field. The structure-property relationship of some Dy(III) based mononuclear SMMs with the SAP configuration was further discussed.

High-Performance Energetic Characteristics and Magnetic Properties of a Three-Dimensional Cobalt(II) Metal-Organic Framework Assembled with Azido and Triazole.

A three-dimensional metal-organic framework based, high-energy-density compound, [Co5(3-atrz)7(N3)3] (3-atrz = 3-amine-1H-1,2,4-triazole), features superior detonation properties, insensitivity, and thermostability. Magnetic studies show that the compound characterizes the coexistence of remarkable coercivity, metamagnetism, long-range ordering, and relaxation dynamics. The heat-capacity measurement confirms the typical long-range antiferromagnetic ordering below 16 K. This difunctional system exemplifies an effective attempt at developing advanced magnetoenergetic materials.

A Dy2 single-molecule magnet with benzoate anions and phenol-O(-) bridging groups.

A Dy2 single-molecule magnet, namely [Dy2(H3L)2(PhCOO)4]·4H2O (1), was obtained from the reaction of Dy(PhCOO)3 with 1,5-bis(2-hydroxy-3-methoxybenzylidene)carbonohydrazide (H4L). Each Dy(III) ion is located in the chelating pocket [DyO8N] formed by the carboxyl-O, phenol-O, carbohydrazide-O and carbohydrazide-N, forming a tricapped trigonal prism configuration. The Dy(III) centers are bridged by the benzoate anions with µ2:η(1),η(2) coordination mode and the phenol-O(-) groups in the form of µ1:η(2), respectively. The appearance of frequency-dependent out-of-phase (χ''M) signals indicates that 1 displays single-molecule magnet (SMM) behaviour. Fits of the ac data gave an energy barrier (Ueff) of 42.7 K with a pre-exponential factor (τ0) of 1.31 × 10(-7) s. The structure-property relationship of some selected Dy2 paradigmatic compounds was further discussed.

A nine-coordinated dysprosium(III) compound with an oxalate-bridged dysprosium(III) layer exhibiting two slow magnetic relaxation processes.

A 2D oxalate-bridged dysprosium(III) compound, formulated as [Dy(C2O4)1.5(H2O)3]n·2nH2O (1), has been hydrothermally isolated. As for compound 1, structural analysis reveals that the nine-coordinated Dy(III) ions reside in a slightly distorted tricapped trigonal prism. Under an applied magnetic field of 700 Oe, the compound was magnetically characterized as a new example that two slow relaxations of the magnetization processes can be observed in a 2D oxalate-bridged dysprosium(III) layer.