Oe Dc Field Research Articles

Field-induced slow magnetic relaxation in a mononuclear Dy(III) complex with octahedral geometry

We have synthesized a mononuclear Dy(III)-based complex, [Dy(CyPh2PO)3Cl3)] (1) (CyPh2PO = cyclohexylbisphenylphosphine oxide), constructed from a phosphine oxide ligand and a light halogen Cl donor. The Dy(III) ion presents an octahedral geometry where two O atoms from two phosphine ligands locate at two vertexes, while the equatorial positions are completed by three Cl anions and a O atom from another phosphine ligand. Magnetism results reveal that slow relaxation of the magnetizations exists in 1 under an extra dc field because of the significant quantum tunnelling of magnetization (QTM) at 0 Oe dc field. The lighter Cl ions in equatorial plane result in a larger effect to QTM, and thus smaller contribution to slow magnetic relaxation.

Spin glass state in Co doped NdMnO3

The temperature-dependent ac susceptibility studies of in-phase component (χ′ac) and out of phase component (χac″) was done on a single phase polycrystalline NdMn0.6Co0.4O3 sample. The measurements were conducted in 4 Oe ac field and 0 Oe dc field at frequencies of 111, 311, 1011, and 1311 Hz. As the frequency increases, the magnitude of χ′ac decreases, and its peak position, corresponding to Tf, moves towards higher temperatures. This strongly suggests the presence of a spin glass (SG) state and the absence of long-range ferromagnetic ordering. The value of relative shift in freezing temperature (δTf) is found to be δTf = 0.0089, which suggests the existence of canonical SG state in NdMn0.6Co0.4O3 sample. To confirm it the ac susceptibility data was further analyzed using Arrhenius, Vogel Fulcher, and Power–law.

Construction of porous 2D Dy3+ metal organic frameworks: solvent responsive magnetic dynamics under 0 Oe dc field and luminescent sensors for Fe3+ ions

The main distinctions between the crystal structures of 1 and 2 arise from the differing solvent molecules residing within the pores interact with the surrounding frameworks.

Slow magnetic relaxation of a {MnIIINaI}n zig-zag chain based single ion magnet

The synthesis using organic Schiff base ligands H2valen, and organic sulfonate ligands Na(4-HBS) in conjunction with Mn(Ac)3⋅2H2O, produces a one-dimensional coordination polymer with the formula {[Mn(valen)Na(4-HBS)2]⋅2CH3OH}n(1) [H2valen=6,6′-((1E,1′E)-(ethane-1,2-diylbis(azaneylylidene))bis(methaneylylidene))bis(2-methoxyphenol); Na(4-HBS)= Sodium 4-hydroxybenzenesulfonate]. Single crystal X-ray diffraction analysis reveals that complex 1 consist of neutral chains with one [Mn(valen)Na]2+ and two 4-HBS−moieties, in which the Mn(III) adopts an elongated octahedral geometry and Na(I) adopts a distorted pentagonal pyramid geometry, respectively. Magnetic investigations indicate the important magnetic anisotropy in the six-coordinated Mn(III) with the zero-field splitting parameter D = -3.2 cm−1. AC measurements suggest that complex 1 displays characteristics of slow magnetic relaxation under a 2000 Oe DC field, indicative of single ion magnet (SIM) behaviour. The effective energy barriers and the pre-exponential factor for complex 1 are determined to be 10.5 cm−1, and 1.36 × 10−7 s, respectively. This research reports not only a rare Mn(III) SIM molecular complex but also provide a potential approach to construct SIM chains.

Synthesis, luminescence and magnetic properties of dinuclear complexes based on a “pincer” Schiff base and different β-diketonate ligands

Twelve new dinuclear rare earth complexes in three series were successfully synthesized with a “pincer” Schiff base H2L and different β-diketonate ligands: Ln2(acac)2(L)2·2C2H5OH (Ln = Eu (1), Tb (2), Dy (3), Er (4)), Ln2(dbm)2(L)2·2C3H7NO (Ln = Eu (5), Tb (6), Dy (7), Er (8), Yb (9)), Ln2(TTA)2(L)2·2H2O (Ln = Eu (10), Tb (11), Dy(12)). (H2L = 3-aminopyrazine-2-carboxylic acid [(2-hydroxybenzylidene)] hydrazide; Hacac = acetylacetone; Hdbm = dibenzoylmethane; HTTA = 2-thiophene trifluoroacetone). These complexes are centrosymmetric dinuclear structures and RE3+ ions are bridged by oxygen atoms in carbonyl of Schiff base to form the core unit of Ln2O2. The characteristic emission peaks of Er3+ and Yb3+ in 4, 8 and 9 can be observed in Near-infrared luminescence spectra, that is confirmed the central ions were sensitized effectively via ligands. Moreover, 1, 5, 6 and 10 were sensitized in various degrees. The dynamic magnetization curves indicate that 3, 7 and 12 are typical SMMs with slow magnetic relaxation behaviors. Their effective energy barriers are 48.20 K (3) and 42.30 K (12) under 3000 Oe dc field and 81.89 K (7) under zero dc field. The pre-exponential factors (τ0) are 1.35 × 10−6 s (3), 1.38 × 10−10 s (7) and 4.93 × 10−6 s (12), respectively. It is confirmed that the magnetic properties of SMMs can be regulated by different β-diketonate ligands.

The Assembly of Grid-type Lanthanide Cluster

A dicompartmental Schiff base ligand was synthesized and used for the assembly of a lanthanide grid-like complex. Dinuclear Dy2 and tetranuclear Dy4 complexes were isolated from the reaction of the ligand with different dysprosium salt. Single crystal X-ray diffractions show that the two DyIII ions in Dy2 are adopted in the N3O coordination pockets of the ligand and further coordinated by water molecules, whereas, for Dy4, the four DyIII ions are clamped by four ligands through their terminal N3O coordination pockets, forming a grid-type assembly. Magnetic studies reveal that complex Dy2 shows field-induced single-molecule magnetic behavior under 1000 Oe dc field, complex Dy4 shows fast relaxation under zero field and field-induced single-molecule magnet (SMM) behavior under 500 Oe. The difference in the magnetic relaxation is related to the various deprotonation of the ligand and distinct topology of the assemblies.

A nonsymmetric Dy2 single-molecule magnet with two relaxation processes triggered by an external magnetic field: a theoretical and integrated EPR study of the role of magnetic-site dilution.

The 1 : 2 reaction between Dy(O2CMe)3·4H2O and 1-acetyl-2-napthol (LH) in MeOH has provided access to the complex [Dy2L6(MeOH)]·MeOH (1·MeOH) in a good yield. The structures of the isomorphous complex 1·MeOH and its doped diamagnetic yttrium analogue [Dy0.14Y1.86L6(MeOH)]·MeOH (Dy@Y2) have been determined by single-crystal X-ray crystallography and characterized based on elemental analyses, IR spectra, and powder X-ray patterns. Combined dc and ac magnetic susceptibility and the magnetization data for 1 suggest that this complex shows slow magnetic relaxation. Under a 0 Oe dc field, a single relaxation mechanism is seen while two magnetization relaxation processes are evident under a 1500 G external magnetic field. The fit to the Arrhenius law has been performed using the 1.8-10 K ac data, affording an effective barrier for the magnetization reversal of 13 K and 7 K under the external dc field. Theoretical studies have been performed using ab initio and density functional methodologies to understand the electronic structure and the magnetic relaxation dynamics resulting from the single DyIII ion as well as from the dinuclear exchange-coupled states. Rich powder EPR spectra at the X-band and Q-band were obtained from Dy@Y2, as well as from the 1·MeOH dimer, while simulation studies revealed the ferromagnetic nature of the interaction between the DyIII ions in accordance with theoretical studies.

Near-infrared luminescence and magnetism of dinuclear lanthanide complexes constructed from a schiff-base and different β-diketonate coligands

Seven new dinuclear lanthanide complexes based on a schiff-base ligand H2L and β-diketonate coligands have been synthesized and characterized: [Eu2(acac)4(HL)2]·3C2H5OH (1), [Ln2(acac)2(HL)4]·6C2H5OH (Ln = Tb(2), Dy(3), Er(4), Yb(5)), [Dy2(bfa)4(HL)2]·2H2O (6), [Dy2(tmhd)2(HL)4] (7) (H2L = 5-methylsalicylaldehyde-2-aminobenzoylhydrazone; Hacac = acetylacetone; Hbfa = benzoyltrifluoroacetylacetone; Htmhd = 2,2,6,6-tetramethylheptane-3,5-dione). These complexes are all centrosymmetric and bridged by phenoxo-O, offered with Ln2O2 cores. Meanwhile, the near-infrared luminescence measurements show that the characteristic emission peaks of ErIII (4) and YbIII (5) ions can be observed, which means the effective sensitization of the ligands. Subsequently, the dynamic magnetization properties studies show that 3, 6 and 7 exhibit slow magnetic relaxation behavior, typical SMM behavior, resulting in an effective barrier of 48.42 K (3) and 54.82 K (6) under an applied 800 Oe dc field, and 60.59 K for 7 under 3000 Oe dc field. In particular, this work demonstrates that the magnetic properties can be modulated by regulating the electron effects of terminal substituents on the coligands.

Multifunctional Binuclear Ln(III) Complexes Obtained viaIn SituTandem Reactions: Multiple Photoresponses to Volatile Organic Solvents and Anticounterfeiting and Magnetic Properties

The design and synthesis of simple lanthanide complexes with multiple functions have been widely studied and have faced certain challenges. Herein, we successfully synthesized the series of binuclear lanthanide complexes [Ln2(L1)2(NO3)4] (HL1 = 2-amino-1,2-bis(pyridin-2-yl)ethanol; Ln = Dy (Dy2), Tb (Tb2), Ho (Ho2) Er (Er2)) via the in situ self-condensation of Ln(NO3)3·6H2O-catalyzed 2-aminomethylpyridine (16 steps) under solvothermal conditions. Dy2 was mixed with different volatile organic solvents, and photoluminescence tests demonstrated that it showed an excellent selective photoresponse to chloroform (CHCl3). Sensing Tb2 on different organic solvents under the same conditions showed that it exhibited excellent selective photoresponse to methanol (CH3OH). Even under EtOH conditions, Tb2 could selectively respond to small amounts of CH3OH. To the best of our knowledge, achieving a selective photoresponse to various volatile organic compounds by changing the metal center of the complex is difficult. Furthermore, we performed anticounterfeiting tests on Tb2, and the results showed significant differences between the anticounterfeiting marks under white light and ultraviolet light conditions. The alternating current susceptibilities of Dy2 suggested that it was a typical single-molecule magnet (SMM) (Ueff = 93.62 K, τ0 = 1.19 × 10-5 s) under a 0 Oe dc field. Ab initio calculations on Dy2 indicated that the high degrees of axiality of the constituent mononuclear Dy fragments are the main reasons for the existence of SMM behavior.

Synthesis, structure and magnetic property of a linear trinuclear Dy(III) single molecular magnet

The Dy(III)-based complexes have garnered intense attention in the past decades due to their fascinating structures and varied magnetic properties. Herein a linear trinuclear Dy(III) complex [Dy3(picO)4(Phen)3(H2O)2]·HpicO·H2O (1) (H2picO = 6-Hydroxypicolinic acid; Phen = 1,10-Phenanthroline) was synthesized by hydrothermal reaction, and characterized by elemental analyses, IR spectroscopy, single-crystal X-ray diffraction analyses, PXRD and magnetic properties. The three Dy(III) ions are coordinated to three different coordination pockets, leading to different magnetic anisotropy. Magnetic studies reveal that it is a single molecular magnet with slow magnetic relaxation under zero dc field at low temperature dominated by Raman and QTM processes. The energy barriers are 30 K and 39 K for the two relaxation processes under 2000 Oe dc field.

Substitution Effects Regulate the Formation of Butterfly-Shaped Tetranuclear Dy(III) Cluster and Dy-Based Hydrogen-Bonded Helix Frameworks: Structure and Magnetic Properties.

The generation of two types of complexes with different topological connections and completely different structural types merely via the substitution effect is extremely rare, especially for -CH3 and -C2H5 substituents with similar physical and chemical properties. Herein, we used 3-methoxysalicylaldehyde, 1,2-cyclohexanediamine, and Dy(NO3)3·6H2O to react under solvothermal conditions (CH3OH:CH3CN = 1:1) at 80 °C to obtain the butterfly-shaped tetranuclear DyIII cluster [Dy4(L1)4(μ3-O)2(NO3)2] (Dy4, H2L1 = 6,6'-((1E,1'E)-(cyclohexane-1,3-diylbis(azanylylidene))bis(methanylylidene))bis(2-methoxyphenol)). The ligand H2L1 was obtained by the Schiff base in situ reaction of 3-methoxysalicylaldehyde and 1,2-cyclohexanediamine. In the Dy4 structure, (L1)2- has two different coordination modes: μ2-η1:η2:η1:η1 and μ4-η1:η2:η1:η1:η2:η1. The four DyIII ions are in two coordination environments: N2O6 (Dy1) and O9 (Dy2). The magnetic testing of cluster Dy4 without the addition of an external field revealed that it exhibited a clear frequency-dependent behavior. We changed 3-methoxysalicylaldehyde to 3-ethoxysalicylaldehyde and obtained one case of a hydrogen-bonded helix framework, [DyL2(NO3)3]n·2CH3CN (Dy-HHFs, H2L2 = 6,6'-((1E,1'E)-(cyclohexane-1,3-diylbis(azanylylidene))bis(methanylylidene))bis(2-ethoxyphenol)), under the same reaction conditions. The ligand H2L2 was formed by the Schiff base in situ reaction of 3-ethoxysalicylaldehyde and 1,2-cyclohexanediamine. All DyIII ions in the Dy-HHFs structure are in the same coordination environment (O9). The twisted S-shaped (L2)2- ligand is linked by a Dy(III) ion to form a spiral chain. The spiral chain is one of the independent units that is interconnected to form Dy-HHFs through three strong hydrogen-bonding interactions. Magnetic studies show that Dy-HHFs exhibits single-ion-magnet behavior (Ueff = 68.59 K and τ0 = 1.10 × 10-7 s, 0 Oe DC field; Ueff = 131.5 K and τ0 = 1.22 × 10-7 s, 800 Oe DC field). Ab initio calculations were performed to interpret the dynamic magnetic performance of Dy-HHFs, and a satisfactory consistency between theory and experiment exists.

Solvent-Induced Structural Diversity and Magnetic Research of Two Cobalt(II) Complexes.

The solvent-induced topological and structural diversities of two Co(II) complexes, namely, [Co(L)2(SCN)2] (Co1) and [Co2(L)2(SCN)(OAc)3] (Co2) (L = 8-methoxyquinoline), were comparatively analyzed. Certain proportions of L, Co(OAc)2·4H2O, and NaSCN were mixed and dissolved in CH3OH at 60 °C to obtain complex Co1. Complex Co2, an asymmetric dinuclear compound, was obtained by simply replacing CH3OH with CH3CN as the solvent. The Co(II) ion in complex Co1 was coordinated by the N4O2 mode provided by two L ligands and two SCN– anions. The two Co(II) ions in Co2 were in the N2O4 and NO5 coordination environment and were linked by two μ2-OAc– bridges and one rare μ3-OAc– bridge. Weak interaction analysis revealed that complexes Co1 and Co2 exhibited 6-connected shp and 14-connected fcu nets, respectively. Magnetic studies showed that Co1 demonstrated single-ion magnet behavior under 2000 Oe. These behaviors are indicative of clearly field-induced single-ion magnetic behavior with Ueff = 34.7(2) K and τ0 = 2.7(2) × 10–7 s under 2000 Oe dc field, respectively. By contrast, Co2 lacked frequency dependence under zero-field conditions. Electrospray ionization mass spectrometry indicated that two complexes were stable in N,N-dimethylformamide.

Field-induced single molecule magnet behavior of a three-dimensional Dy(III)-based complex

A novel three-dimensional Dy(III)-based complex [Dy(H2-DHBDC)0.5(DHBDC)0.5(C2H5OH)(H2O)]n·H2O (H4-DHBDC = 2,5-dihydroxy-1,4-terephthalic acid) (1) was fabricated using a hydrothermal method. Such complex was examined by single-crystal X-ray diffraction analysis and then characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, powder X-ray diffraction as well as magnetic properties. The results of single-crystal structure analysis suggested that complex 1 consisted of three-dimensional framework structure and crystallized in the monoclinic system, space group P21/c. The DyIII ion in 1 adopted eight-coordination mode with a triangular dodecahedron. The results of magnetic property investigations suggested that the coordination polymer exhibited slow magnetic relaxation behaviors under 1500 Oe dc field. Furthermore, the frequency dependence of out-of phase (χ″) ac signals for complex 1 displayed two maxima at low temperature, indicating the presence of two relaxation processes.

A New Family of 2D Coordination Polymers Based on 3d‐4f 15‐Metallacrown‐5 Units: Synthesis, Structure, and Single‐Molecule Magnet Behavior

A new family of 2D coordination polymers based on 3d‐4f 15‐metallacrown‐5 (MC) units were designed and characterized. The connection of the 15‐metallacrown‐5 subunits by the coordination of CuII and ligand led to the formation of 2D network of metallacrowns. Analysis of the magnetic properties of these coordination polymers reveals that the GdIII (1), TbIII (2), and DyIII (3) complexes exhibit slow magnetic relaxation and under 1000 Oe dc field, and the DyIII (3) complex exhibits single‐molecule magnet behavior.

Trinuclear and Hexanuclear Lanthanide(III) Complexes of the Chiral 3+3 Macrocycle: X-ray Crystal Structures and Magnetic Properties

A new triphenolic hexaaza chiral macrocyclic amine L forms trinuclear complexes 1-3 with rare earth metal lanthanide(III) ions (Ln = Dy, Eu, and Y) with the general formula [Ln3L(μ3-OH)2(NO3)4(H2O)2]· xCH3OH. The crystal structures of the nitrate derivatives of this type reveal the presence of a {Ln3(μ3-OH)2} core within the macrocycle. For the chloride derivative of dysprosium(III) 4, a duplex of the trinuclear compound is formed to give the hexanuclear [Dy6L2(μ3-OH)3(μ3-O)(μ2-Cl)3Cl4(H2O)2] compound, in which two trinuclear macrocyclic units are linked by bridging chloride anions, supplemented by a hydrogen bond connecting the central oxo and hydroxo bridges as well as by weak interactions at the periphery of the macrocycle. The nuclear magnetic resonance spectra of these complexes reveal a dynamic behavior in solution related to exchange of axial ligands and hindered rotation of phenyl substituents. Magnetic studies of the nitrate (1-3) and chloride (4) dysprosium(III) complexes suggest the presence of weak ferromagnetic interactions between neighboring metal centers. The interaction is strongest for compound 1, and for the related duplex compound 4, it appears to be somewhat weaker. The ac susceptibility measurements for complexes 1 and 4 confirm their field-induced single-molecule magnet behavior with the following characteristics: Ueff = 10.6 cm-1 (15.2 K), τ0 = 2.05 × 10-4 s under 2500 Oe dc fields for 1; Ueff = 7.9 cm-1 (11.4 K), τ0 = 1.68 × 10-4 s under a 3000 Oe dc field for 4.

Mononuclear dysprosium complex with single-ion magnetic behavior and its highly selective detection of 1,4-dioxane

The organic ligand 5,7-dibromo-2-methyl-8-quinolinol (L) was used to react with Dy(NO3)3·6H2O at 60 °C to obtain the complex [Dy(L)3(CH3CH2OH)(H2O)]·CH3CN (1). Furthermore, the electrospray mass spectrometry (ESI–MS) data show that the main molecular fragment was [DyL2(DMF)2]+ under the condition of 0 eV voltage. When complex 1 was dissolved in DMF and stayed for half a month, and it also showed the main molecular fragment after measuring ESI–MS. So complex 1 was relatively stable in DMF. And magnetic susceptibilities showed that 1 exhibits a clear field-induced SIM behavior, and the energy barriers and extrapolated relaxation time was Ueff = 14.6 K and τ0 = 4.1 × 10−5 s under 1000 Oe dc field. The complex 1 was dissolved in various organic solvents and tested for fluorescence. It was found to have very high selectivity in 1,4-dioxane and the fluorescence intensity was more than 3 times that of other organic solvents.

Synthesis, Crystal Structures, and Magnetic Properties of New Hexanuclear MnIII2LnIII4 Complexes: SMM Behavior of the Terbium(III) Analogue

This investigation reports the syntheses, crystal structures, and magnetic properties of a series of isomorphous hexanuclear MnIII2LnIII4 compounds of composition [MnIII2LnIII4L12L22(µ3‐OH)4(µ1,3‐Pivalate)6(NO3)2]·2CH3CN {Ln = Tb (1), Dy (2), Ho (3), Er (4)}, where H2L1 is the Schiff base ligand that is obtained by [1+1] condensation of 3‐methoxysalicylaldehyde (HL2) with 2‐amino‐2‐methyl‐1‐propanol. While the O(phenoxo)N(imine)O(alkoxo) pocket of the ligand [L1]2– binds a MnIII ion, the other pocket, O(methoxy)O(phenoxo), remains noncoordinated. In contrast, each of the O(methoxy)O(phenoxo) and O(phenoxo)O(aldehyde) sites of [L2]– is occupied by a LnIII ion. Additionally, there are four µ3‐hydroxo, six µ1,3‐pivalate, and two chelating nitrate ligands, stabilizing the hexanuclear cores. Magnetic susceptibility (2–300 K) and magnetization (M) data reveal significant anisotropy in 1–4. Detailed ac susceptibility measurements have revealed single molecule magnet (SMM) behavior in the TbIII analogue with Ueff = 11.12 cm–1 and τ0 = 1.04 × 10–7 s under a 1000 Oe dc field and Ueff = 10.42 cm–1 and τ0 = 1.62 × 10–7 s under a 3500 Oe dc field, while the other three analogues do not show slow relaxation of magnetization.

Synthesis, structure and slow magnetic relaxation of a linear Ho4 cluster

A new Ho4 cluster, namely, [Ho4(tmhd)8(L)2(CH3OH)2]·CH3OH (1) (tmhd = 2,2,6,6‑tetramethyl‑3,5‑heptanedione, H3L = 2‑[(2‑(hydroxyimino)propanehydrazide)methyl]), has been successfully synthesized via using a multidentate Schiff base ligand, and further characterized by crystallography. Structural analysis shows that four HoIII ions in cluster 1 are linearly arranged. The magnetic study reveals that 1 exhibits slow magnetic relaxation under zero dc field. When under an external 3000 Oe dc field, we obtained the effective energy barrier ΔE/kB = 13.8 K and the pre-exponential factor τ0 = 2.8 × 10−6 s.

A new β-diketonate Dy(III) single‒ion magnet featuring multiple magnetic relaxation processes

A β-diketonate mononuclear dysprosium compound, [Dy(TFNB)3(bpy)] (1) (TFNB = 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione, bpy = 2,2′-bipyridine), has been prepared and structurally and magnetically characterized. X-ray crystallographic analysis reveals that 1 contains two crystallographically equivalent Dy(III) ions of which the eight-coordinate geometries uniformly behave as distorted square antiprismatic configurations (D4d). Magnetic investigations demonstrate that 1 displays dual relaxation processes of SMMs behavior with the effective barrier (ΔE/kB) of 23.44 K under 1200 Oe DC field, corresponding to the coexistence of two metal centers in the structure of the compound. The comparative studies of some Dy(III)-based SIMs with TFNB ligand have been conducted as well. Ab initio studies demonstrate that the Kramers doublet ground state is predominantly axial with the gz tensors of two Dy(III) fragments matching the Ising-limit factor (20) anticipated for the pure MJ = ±15/2 state.

Near-infrared luminescence and solvent modulation of the magnetic relaxation behavior of dinuclear lanthanide complexess

Seven new dinuclear centrosymmetric complexes, [Ln2(dbm)2L2(DMF)2]·2DMF (Ln = Nd (1), Eu (2), Tb (3), Dy (4), Er (5), Yb (6)) and [Dy2(dbm)2L2(CH3OH)2]·2CH3OH (7) (Hdbm = 1,3-diphenyl-1,3-propanedione, H2L = 2-[(2-(amino)benzhydrazide)-methyl]-8-hydroxylquinoline, DMF = dimethyl-formamide) have been synthesized and structurally characterized. Dynamic magnetic studies reveal the slow magnetic relaxation of complexes 4 and 7 are influenced by a fast quantum tunneling relaxation of the magnetization (QTM). However, the different magnetic relaxation behaviors were observed apparently in the two Dy2 complexes under a 3000 Oe dc field and modulated by the subtle change of solvents from DMF to CH3OH. For complex 7, the temperature dependence curves of in-phase (χ′) and out-of-phase (χ″) show better frequency-dependent signals, suggesting a slow relaxation of magnetization, typical of SMM behavior. Fitting the dynamic magnetic data of complex 7 to the Arrhenius law gives the energy barrier Ueff/kB = 44.06 K with the pre-exponential factor τ0 = 2.17 × 10−7 s under a 3000 Oe dc field.