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Article

Two Dy2 Zero-Field Single-Molecule Magnets Derived from Hydrazone Schiff Base-Bridging Ligands and 1,3-Di(2-pyridyl)-1,3-propanedione †

by
Cai-Ming Liu
Beijing National Laboratory for Molecular Sciences, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China
†
Dedicated to Prof. Dai-Zheng Liao on the occasion of his 85th birthday.
Magnetochemistry 2025, 11(7), 58; https://doi.org/10.3390/magnetochemistry11070058
Submission received: 27 May 2025 / Revised: 25 June 2025 / Accepted: 30 June 2025 / Published: 2 July 2025
(This article belongs to the Special Issue Molecular Magnetism: A Themed Issue in Honor of Professor Dai-Zheng Liao on the Occasion of His 85th Birthday)
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Abstract

Two hydrazone Schiff base-bridging ligands with different heterocycles {2-[(E)-(5-chloro-2-hydroxyphenyl)methylidene]diazanyl}(pyrazine-2-yl)methanone (H2LSchiff-1) and (E)-N′-(2-hydroxy-3-methoxybenzylidene)nicotinohydrazide (H2LSchiff-2) together with 1,3-di(2-pyridyl)-1,3-propanedione (Hdpp) were chosen to construct two new Dy2 complexes, [Dy2(LSchiff-1)2(DMF)2(dpp)2]·0.5DMF (1) and [Dy2(LSchiff-2)2(DMF)2(dpp)2]·2DMF (2). Although the [N2O6] coordination spheres are observed for the Dy3+ ions in 1 and 2, their coordination configurations have some differences (both the biaugmented trigonal prism and the Snub diphenoid J84 in 1 and only the biaugmented trigonal prism in 2). Magnetic research revealed that both 1 and 2 possess ferromagnetic interactions between two Dy3+ ions and perform as zero-field single-molecule magnets, with Ueff/k values of 49.7 K at 0 Oe for 1 and 151.8 K at 0 Oe for 2. This work suggests that the heterocycle groups (pyrazine vs. pyridine) on the hydrazone Schiff base-bridging ligands have effects on the SMM properties of 1 and 2.

1. Introduction

Single-molecule magnets (SMMs) are an important branch of molecular magnets, and their magnetic bistable properties at the nanoscale have potential applications in high-density information storage, quantum computing, and other related fields [1]. Since lanthanide ions, especially the dysprosium (III) ion, naturally have significant magnetic anisotropy and multiple unpaired electrons (corresponding to large ground-state spin values), lanthanide SMMs have become the most developed SMMs in recent years [2]. Among them, the energy barrier (Ueff) value and magnetic blocking temperature (TB) of the SMM containing a single lanthanide ion, that is, the single-ion magnet (SIM), can reach a high level [3,4,5,6,7,8], but the sensitivity of metal–organic compounds to air will affect the application of this type of SMMs; while the SMM containing multiple lanthanide ions, requires consideration of the consistency of the magnetic axis orientation of each lanthanide ion [9], its Ueff value and TB value are more difficult to make a big breakthrough. There is no doubt that the magnetic axis orientation consistency of the Ln(III) binuclear SMM is the easiest to achieve among the SMMs with multiple lanthanide (III) ions, which can be achieved through the ferromagnetic interaction between two lanthanide (III) ions [10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29]. Notably, the ferromagnetic interaction can partially or completely quench quantum tunneling of magnetization (QTM), activating SMM behavior at zero dc field [11]. However, the magnetic interactions between 4f and 4f electrons are usually difficult; even if magnetic exchange occurs, it often exhibits weak antiferromagnetic coupling.
Hydrazone Schiff base-bridging ligands are commonly used to construct Ln SMMs [30,31]; they have been used to construct some ferromagnetically coupled Dy2 SMMs [10,11,12,13,14,32,33,34,35,36,37,38], the magnetic properties of which may be affected by several factors. For example, the coordination anion [32], and the substituent on the terminal ligands [33] are the most common influencing factors. From the perspective of molecular engineering, heterocycles on hydrazone Schiff base-bridging ligands are also important influencing factors. Recently, we used two hydrazone Schiff bases (Scheme 1) with different heterocycles (pyrazine vs. pyridine) as bridging ligands and both 1,3-di(2-pyridyl)-1,3-propanedione (Hdpp) (Scheme 1) and DMF as terminal ligands to construct two new Dy2 complexes: [Dy2(LSchiff-1)2(DMF)2(dpp)2]·0.5DMF {H2LSchiff-1 = {2-[(E)-(5-chloro-2-hydroxyphenyl)methylidene]diazanyl}(pyrazine-2-yl)methanone} (1) and [Dy2(LSchiff-2)2(DMF)2(dpp)2]·2DMF {H2LSchiff-2 = (E)-N’-(2-hydroxy-3-methoxybenzylidene)nicotinohydrazide} (2), which exhibit ferromagnetic interactions and perform zero-field SMM properties, with Ueff/k values of 49.7 K and 151.8 K at 0 Oe for 1 and 2, respectively, suggesting that the heterocycles on hydrazone Schiff base-bridging ligands have an effect on the magnetic properties of Dy2 SMMs.

2. Results

2.1. Crystal Structures

Dy2 complexes 1 and 2 are crystallized in P-1 space group and P21/c space group, respectively. As shown in Figure 1, there are two crystallographically independent molecules in 1, each consisting of two Dy3+ ions, two LSchiff-12− bridging ligands, two dpp− terminal ligands, and two coordinated DMF molecules. In addition, the lattice of 1 contains DMF solvent molecules. Notably, both independent molecules are centrosymmetric; consequently, the anisotropy axes of the two ferromagnetic Dy3+ ions in 1 have to be parallel to each other, which may be beneficial to its SMM properties. The asymmetric unit is composed of one Dy3+ ion, one LSchiff-12− bridging ligand, one dpp− terminal ligand, and one coordinated DMF molecule. In each molecule the two LSchiff-12− bridging ligands chelate two Dy3+ ions from opposite positions to form a rough plane; a dpp− terminal ligand and a DMF molecule then coordinate each dysprosium (III) ion from the upper and lower directions of the plane, and a [N2O6] coordination sphere is formed, which is coordinated by one Npyrazine atom and Oacyl atom from one LSchiff-12− ligand, one Nimine atom, one Oacyl atom and one Ophenol atom from the other LSchiff-12− ligand, two O atoms from the dpp− terminal ligand, and one ODMF atom. Further analysis with the SHAPE 2.1 software [39] revealed that the coordination configurations of Dy1 and Dy2 are the biaugmented trigonal prism and Snub diphenoid J84, respectively, with CShM values of 1.818 for the C2v symmetry and 20.565 for the D2d symmetry (Table S1). Notably, the pyridine N atom in the dpp− terminal ligand does not participate in the coordination, unlike some SMMs containing lanthanide (III) ions [40,41]. The Dy1–Dy1#1 (#1 1 − x, 2 − y, 1 − z) distance (3.942 Å) is a little longer than the Dy1-Dy1#2 (#2 −x, 1 − y, 2 − z) distance (3.932 Å). The mean distance of Dy1–O (2.324 Å) is comparable with that of Dy2–O (2.321 Å), and the average distance of Dy1–N (2.541 Å) is comparable with that of Dy2–N (2.541 Å) (Table 1). Notably, the latest CCDC retrieval revealed that 1 represents the first complex derived from the new H2LSchiff-1 ligand.
As shown in Figure 2, the main structure of 2 is composed of two Dy3+ ions, two LSchiff-22− bridging ligands, two dpp− anions, and two coordinated DMF molecules. Additionally, 2 contains some DMF solvent molecules in its lattice as well. Different from 1, only one crystallographically independent molecule exists in 2; there is a symmetry center in this molecule as well, and the asymmetric unit is composed of one Dy3+ ion, one LSchiff-22− bridging ligand, one dpp− anion, and one coordinated DMF molecule. Similar to 1, the two LSchiff-22− bridging ligands in 2 coordinate two Dy3+ ions to form a rough plane; and a dpp− anion and a DMF molecule then finish the coordination of the Dy3+ ion, generating a [N2O6] coordination sphere. Each Dy3+ cation is coordinated by one Npydine atom and Oacyl atom of one LSchiff-22− ligand, one Nimine atom, one Oacyl atom and one Ophenol atom of the other LSchiff-22− ligand, two O atoms of the dpp− anion, and one ODMF atom. The coordination configuration of Dy1 in 2 is the biaugmented trigonal prism, with a CShM value of 2.247 for the C2v symmetry (Table S2). The Dy1–Dy1#3 (#3 1 − x, 1 − y, 1 − z) distance in 2 (3.885 Å) is slightly shorter than the Dy–Dy distance in 1 (3.942 Å and 3.932 Å) (Table 1 and Table 2). The mean distance of Dy1–O in 2 (2.315 Å) is slightly shorter than those of Dy–O in 1 (2.324 Å and 2.321 Å), and the average distance of Dy1–N in 2 (2.525 Å) is a little smaller than those of Dy–N in 1 (2.541 Å and 2.541 Å) (Table 1 and Table 2). However, the Dy1–O3–Dy1#3 bond angle in 2 {113.95(8)°} is slightly larger than the corresponding Dy–O–Dy bond angles in 1 {112.7(2)° and 112.6(2)°} (Table 1 and Table 2).

2.2. Magnetic Properties

The thermal variation of χMT in the range of 2–300 K for 1 and 2 at 1000 Oe is shown in Figure 3. The χMT values at 300 K are 28.36 cm3 K mol−1 for 1 and 28.37 cm3 K mol−1 for 2, both are very close to the theoretical value of the two separated Dy3+ ions (28.34 cm3 K mol−1). Their χMT values all decrease slowly with the decrease in temperature, reaching minimums of 27.04 cm3 K mol−1 at 42 K for 1 and 28.12 cm3 K mol−1 at 55 K for 2, and then increasing sharply to 40.32 cm3 K mol−1 for 1 and 41.67 cm3 K mol−1 for 2 at 2 K. Such a trend of the χMT–T curve is caused by two factors, the depopulation of Mj levels of the Dy3+ ion and the intramolecular ferromagnetic interaction between the two Dy3+ ions [10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28]. More and more ferromagnetic Dy2 SMMs based on hydrazine Schiff base ligands have been explored (Table 3), in which the Dy···Dy distance, the Dy–O bond distance and the Dy–O–Dy angle of the Dy2O2 core are important parameters that determine whether a ferromagnetic interaction is formed or not, because these three factors have a subtle regulation of the overlap between the magnetic orbitals of the two Dy3+ ions, thus affecting their magnetic interactions. As can be seen from Table 3, the ferromagnetic interaction can be formed in the range of 3.864–3.992 Å of the Dy···Dy distance, 2.317–2.380 Å of the average Dy–O bond distance, and 108.9–115.1° of the Dy–O–Dy angle for the eight-coordinate sphere. However, in the case of a nine-coordinate sphere [42], the ferromagnetic interaction may not be formed when the average Dy–O bond length is greater than 2.400 Å (Table 3). The field-variable magnetization of 1 and 2 at different low temperatures was then determined, and their M–H/T curves at 2–6 K do not coincide together (Figures S1 and S2), suggesting possible magnetic anisotropy.
The measurement of ac magnetic susceptibility revealed that both 1 and 2 are zero-field SMMs. As shown in Figure 4a, at 0 Oe the χ” versus T curves at 50–1399 Hz of 1 show clear frequency dependence, and peaks can be observed in the range of 250–1399 Hz. On the other hand, the χ” versus ν curves at 0 Oe of 1 also display frequency dependence, and peaks can be observed in the range of 2.0–6.5 K (Figure 4b). The ln(τ)–1/T plot based on these χ” versus ν curves is a curve rather than a straight line (Figure 4c), suggesting that the magnetic relaxation of 1 includes other processes such as the quantum tunneling of magnetization (QTM), the Raman process in addition to the Orbach process; therefore, this curve was fitted with τ−1 = τQTM−1 + CTn + τ0−1exp(−Ueff/kT), giving τQTM = 0.0145 s, n = 2.46, C = 1.33 s−1 K−2.46, Ueff/k = 49.7 K and τ0 = 7.9 × 10−6 s. The τ0 value of 1 (7.9 × 10−6 s) is normal for the Dy(III) SMMs (10−6 s–10−11 s) [2], and its n value of 2.46 is also within the normal range (2 < n < 9). Since the crystal structure of 1 contains two types of coordination configurations of the Dy3+ ions, its Cole–Cole curves at 0 Oe could be fitted with the sum of two modified Debye functions [43,44,45,46] (Figure 4d), giving α1 values of 0.276–0.385, and α2 values of 0.001–0.108. Moreover, no hysteresis loop can be formed at 1.9 K for 1 (Figure S3). The magnetic axes of 1 could be calculated with the electrostatic model implemented in the Magellan program [47]; as expected, the two magnetic axes in each independent molecule are arranged in perfect parallel (Figure S4).
We also investigated the effect of 1500 Oe, a commonly used dc magnetic field, on the magnetic relaxation of 1. As shown in Figure 5a, at 1500 Oe the χ” versus T curves of 1 show more clear frequency dependence, and peaks can be observed in a wider range of 10–1399 Hz with respect to 0 Oe. The χ” versus ν curves at 1500 Oe of 1 are also frequency-dependent, but peaks can be observed in a narrower range of 3.0–6.5 K with respect to 0 Oe (Figure 5b). The ln(τ)–1/T plot at 1500 Oe of 1 is still a curve (Figure S5), which was fitted using τ−1 = AT + CTn + τ0−1exp(−Ueff/kT), giving A = 0.892, n = 5.91, C = 0.00352 s−1 K−5.91, Ueff/k = 87.6 K and τ0 = 2.4 × 10−9 s. Similar to other zero-field Dy2 SMMs [30,32,33,34], the dc magnetic field (here is 1500 Oe) can partially or completely inhibit QTM, resulting in an increase in the Ueff/k value of 1 (from 49.7 K to 87.6 K) and a decrease in the τ0 value (from 7.9 × 10−6 s to 2.4 × 10−9 s).
The χ” versus T curves at 0 Oe of 2 show obvious frequency dependence (Figure 6a), and peaks appear in the range of 10–1399 Hz, which is larger than that of 1 (250–1399 Hz). On the other hand, the χ” versus ν curves at 0 Oe of 2 are also frequency-dependent (Figure 6b), and peaks appear in the range of 5–15 K; the peak temperatures of 2 are obviously higher than those of 1 at 0 Oe. The ln(τ)–1/T plot derived from the χ” versus ν curves of 2 is a curve as well (Figure 6c), which could be fitted with τ−1 = CTn + τ0−1exp(−Ueff/kT), yielding n = 5.56, C = 0.00014 s−1K−5.56, Ueff/k = 151.8 K, and τ0 = 5.2 × 10−8 s. The τ0 value at 0 Oe of 2 (5.2 × 10−8 s) is smaller than that of 1 (7.9 × 10−6 s); the Ueff/k value at 0 Oe of 2 (151.8 K) is comparable with those of other ferromagnetic Dy2 SMMs based on hydrazine Schiff base ligands and achiral β-diketonate ligands [33] or homochial β-diketonate ligands [36], which is about three times that of 1 (49.7 K). The Cole–Cole curves at 0 Oe of 2 could be fitted by a generalized Debye model [48,49] (Figure 6d), giving small α values in the range of   0.00051–0.01061, suggesting narrow relaxation time distribution. In addition, at 1.9 K no hysteresis loop may be observed for 2 (Figure S6). Due to the presence of a center of symmetry in the molecule, the two magnetic axes of 2 are also perfectly parallel (Figure S7).
Similarly, we also studied the effect of 1500 Oe dc field on the magnetic relaxation of 2. As shown in Figure 7a, at 1500 Oe the χ” versus T curves of 2 possess obvious frequency dependence, and peaks may be observed in the same range of 10–1399 Hz as at 0 Oe. The χ” versus ν curves at 1500 Oe of 2 are frequency-dependent as well, but peaks appear in a narrower range of 6–15 K with respect to 0 Oe (Figure 7b). The ln(τ)–1/T plot at 1500 Oe of 2 is also a curve (Figure S8), which could also be fitted with τ−1 = AT + CTn + τ0−1exp(−Ueff/kT), calculating A = 0.211, n = 5.95, C = 0.00006 s−1 K−5.95, Ueff/k = 157.9 K, and τ0 = 5.1 × 10−8 s. Similar to 1, the dc magnetic field of 1500 Oe may partially or completely inhibit QTM, which results in an increase in the Ueff/k value of 2 (from 151.8 K to 157.9 K) and a decrease in the τ0 value (from 5.2 × 10−8 s to 5.1 × 10−8 s). However, the variation amplitude of 2 is smaller than that of 1, indicating that the QTM effect of 2 is much weaker than that of 1.
It can be seen that although both 1 and 2 have a [N2O6] coordination sphere, the change in heterocyclic groups (pyrazine vs. pyridine) on the hydrazone Schiff base-bridging ligand can lead to significant changes in the SMM properties of 1 and 2 (e.g., magnetic relaxation, QTM, energy barrier value, etc.). This is related to the difference in their coordination configurations.

3. Conclusions

In summary, two new Dy2 zero-field SMMs have been assembled using two hydrazone Schiff base-bridging ligands with different heterocycles (pyrazine vs. pyridine) as the bridging ligand and 1,3-di(2-pyridyl)-1,3-propanedione as the terminal ligand. The ferromagnetic interactions between two Dy3+ ions exist in both complexes. As expected, they have different Ueff/k values (49.7 K and 151.8 K at 0 Oe for 1 and 2, respectively). This work demonstrates that the Dy2 SMMs’ magnetic properties can be adjusted by the change in the heterocycle groups (pyrazine vs. pyridine) on the hydrazone Schiff base-bridging ligands. Such molecular engineering provides a good way to design lanthanide SMMs with better performance.

4. Materials and Methods

4.1. General Remarks

The C, H, N elemental analyses were carried out on a Thermo Flash EA1112 elemental analyzer (Thermo Fisher Scientific, Waltham, MA, USA). The infrared spectra were performed on a Bruker VERTEX 70v spectrophotometer (Bruker, Karlsruhe, Germany) with pressed KBr disk. The magnetic susceptibility measurements were measured on a Quantum Design MPMS-XL5 SQUID magnetometer (Quantum Design, San Diego, CA, USA). Diamagnetic corrections were estimated using Pascal’s constants for all constituent atoms of 1 and 2.

4.2. Preparation of H2LSchiff-1

A mixture of 5-chlorosalicylaldehyde (1565.7 mg, 10 mmol) and pyrazinoic acid hydrazide (1381.3 mg, 10 mmol) was added into 60 mL of MeOH; the mixture was refluxed for 3 h to form a light yellow precipitate, which was naturally cooled and then collected by filtration. Yield: 90%. Anal. Calcd. (%) for C12H9ClN4O2 (H2LSchiff-1): C, 52.09; H, 3.28; N, 20.25%. Found: C, 52.01; H, 3.32; N, 20.17%.

4.3. Preparation of 1

H2LSchiff-1 (66.9 mg, 0.25 mmol), 1,3-di(2-pyridyl)-1,3-propanedione (56.6 mg, 0.25 mmol), LiOH·H2O (31.5 mg, 0.75 mmol), and Dy(ClO4)3·6H2O (142.2 mg, 0.25 mmol) were added into 15 mL of DMF, this mixture was stirred for 10 h to form yellow precipitates, which were dissolved after adding 20 mL of methanol and 20 mL of CH2Cl2 to obtain a yellow solution, and yellow single crystals were grown after slowly volatilizing the solvent. Yield: 55% based on Dy. Anal. Calcd. (%) for C57.5H47.5Cl2Dy2N14.5O10.5 (1): C, 45.87; H, 3.18; N, 13.49%. Found: C, 45.81; H, 3.22; N, 13.43%. IR (KBr): ν = 3422(b,w), 3052(w), 3000(w), 2929(w), 2889(w), 1659(s), 1606(s), 1553(s), 1524(s), 1507(s), 1470(s), 1399(s), 1365(m), 1340(m), 1311(w), 1284(w), 1255(w), 1240(w), 1171(w), 1156(w), 1112(w), 1088(w), 1050(w), 1032(w), 1007(w), 994(w), 973(w), 948(w), 906(w), 875(w), 861(w), 828(w), 808(w), 774(w), 752(m), 716(m), 684(w), 653(w), 610(w), 553(w), 534(w), 506(w), 474(w), 451(w), 429(w) cm−1.

4.4. Preparation of 2

H2LSchiff-2 (64.8 mg, 0.25 mmol), 1,3-di(2-pyridyl)-1,3-propanedione (56.6 mg, 0.25 mmol), LiOH·H2O (31.5 mg, 0.75 mmol), and Dy(ClO4)3·6H2O (142.2 mg, 0.25 mmol) were added into 5 mL of DMF; this mixture was stirred for 10 h to form yellow precipitates, which were dissolved after adding 15 mL of methanol and 20 mL of CH2Cl2 to obtain a yellow solution, and yellow single crystals were grown after slowly volatilizing the solvent. Yield: 45% based on Dy. Anal. Calcd. (%) for C66H68Dy2N14O14 (2): C, 49.35; H, 4.27; N, 12.21%. Found: C, 49.25; H, 4.31; N, 12.15%. IR (KBr): ν = 3415(b,w), 3131(w), 3045(w), 2998(w), 2930(w), 2898(w), 2826(w), 1656(s), 1603(s), 1555(s), 1521(s), 1505(s), 1473(s), 1453(s), 1402(s), 1343(m), 1315(w), 1286(w), 1235(m), 1212(m), 1163(w), 1102(w), 1082(w), 1045(w), 1015(w), 993(w), 968(w), 949(w), 919(w), 861(w), 806(w), 740(m), 718(w), 694(w), 668(w), 635(w), 610(w), 587(w), 536(w), 493(w), 475(w), 456(w), 426(w) cm−1.

4.5. X-Ray Crystallography

The intensity data collection of 1 and 2 was curried on a Rigaku MM007HF diffractometer (Rigaku, Tokyo, Japan) with Mo-Kα radiation (λ = 0.71073 Å) at 170 K. The structures were solved using the olex2.solve structure solution program and refined using the ShelXL-2018 refinement package. All non-hydrogen atoms were refined anisotropically, and the hydrogen atoms were refined as riding atoms. Selected crystal data and structural refinement parameters for 1 and 2 are listed in Table 4.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/magnetochemistry11070058/s1, Table S1, Dy (III) ion geometry analysis by SHAPE 2.1 software for 1; Table S2, Dy (III) ion geometry analysis by SHAPE 2.1 software for 2; Figure S1, M versus H/T plots at 2–6 K of 1; Figure S2, M versus H/T plots at 2–6 K of 2; Figure S3, Hysteresis loop for 1 at 1.9 K; Figure S4, Magnetic axes of the Dy3+ ions in 1 calculated using an electrostatic model; Figure S5, Plot of lnτ versus 1/T for 1 (Hdc = 1500 Oe); Figure S6, Hysteresis loop for 2 at 1.9 K; Figure S7, Magnetic axes of the Dy3+ ions in 2 calculated using an electrostatic model; Figure S8, plot of lnτ versus 1/T for 2 (Hdc = 1500 Oe). CCDC 2454030-2454031 contain the supplementary crystallographic data for 1 and 2. These data can be obtained free of charge via https://www.ccdc.cam.ac.uk/, or from the Cambridge Crystallographic Data Center, 12 Union Road, Cambridge CB2 1EZ, UK; e-mail: deposit@ccdc.cam.ac.uk.

Funding

This research was funded by the National Natural Science Foundation of China (22271289 and 21871274).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in this study are included in the article/Supplementary Materials. Further inquiries can be directed to the corresponding author.

Conflicts of Interest

The author declares no conflicts of interest.

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Magnetochemistry 11 00058 sch001
Scheme 1. Hydrazone Schiff bases (H2LSchiff-1 and H2LSchiff-2) and 1,3-di(2-pyridyl)-1,3-propanedione (Hdpp).
Scheme 1. Hydrazone Schiff bases (H2LSchiff-1 and H2LSchiff-2) and 1,3-di(2-pyridyl)-1,3-propanedione (Hdpp).
Magnetochemistry 11 00058 sch001
Magnetochemistry 11 00058 g001
Figure 1. Crystal structure of 1, all H atoms and solvent molecules are omitted for clarity. Symmetry code: #1 1 − x, 2 − y, 1 − z; #2 −x, 1 − y, 2 − z.
Figure 1. Crystal structure of 1, all H atoms and solvent molecules are omitted for clarity. Symmetry code: #1 1 − x, 2 − y, 1 − z; #2 −x, 1 − y, 2 − z.
Magnetochemistry 11 00058 g001
Magnetochemistry 11 00058 g002
Figure 2. Crystal structure of 2, all H atoms and solvent molecules are omitted for clarity. Symmetry code: #3 1 − x, 1 − y, 1 − z.
Figure 2. Crystal structure of 2, all H atoms and solvent molecules are omitted for clarity. Symmetry code: #3 1 − x, 1 − y, 1 − z.
Magnetochemistry 11 00058 g002
Magnetochemistry 11 00058 g003
Figure 3. Plots of χMT versus T of 1 and 2 measured under a 1000 Oe dc field.
Figure 3. Plots of χMT versus T of 1 and 2 measured under a 1000 Oe dc field.
Magnetochemistry 11 00058 g003
Magnetochemistry 11 00058 g004
Figure 4. χ” versus T curves for 1 (Hdc = 0 Oe) (a); χ” versus ν curves at 2.0 to 6.5 K for 1 (Hdc = 0 Oe) (b); plot of ln(τ) versus 1/T for 1 (Hdc = 0 Oe), the solid line represents the best fitting with QTM + Raman + Orbach (c); Cole–Cole curves at 2.0 to 6.5 K for 1 (Hdc = 0 Oe), the solid lines represent the best fitting with the sum of two modified Debye functions [43,44,45,46] (d).
Figure 4. χ” versus T curves for 1 (Hdc = 0 Oe) (a); χ” versus ν curves at 2.0 to 6.5 K for 1 (Hdc = 0 Oe) (b); plot of ln(τ) versus 1/T for 1 (Hdc = 0 Oe), the solid line represents the best fitting with QTM + Raman + Orbach (c); Cole–Cole curves at 2.0 to 6.5 K for 1 (Hdc = 0 Oe), the solid lines represent the best fitting with the sum of two modified Debye functions [43,44,45,46] (d).
Magnetochemistry 11 00058 g004
Magnetochemistry 11 00058 g005
Figure 5. χ” versus T curves for 1 (Hdc = 1500 Oe) (a); χ” versus ν curves at 2.0 to 6.5 K for 1 (Hdc = 1500 Oe) (b).
Figure 5. χ” versus T curves for 1 (Hdc = 1500 Oe) (a); χ” versus ν curves at 2.0 to 6.5 K for 1 (Hdc = 1500 Oe) (b).
Magnetochemistry 11 00058 g005
Magnetochemistry 11 00058 g006
Figure 6. χ” versus T curves for 2 (Hdc = 0 Oe) (a); χ” versus ν curves at 5 to 15 K for 2 (Hdc = 0 Oe) (b); plot of ln(τ) versus 1/T for 2 (Hdc = 0 Oe), the solid line represents the best fitting with Raman + Orbach (c); Cole–Cole curves at 5 to 15 K for 2 (Hdc = 0 Oe), the solid lines represent the best fitting with a generalized Debye model [48,49] (d).
Figure 6. χ” versus T curves for 2 (Hdc = 0 Oe) (a); χ” versus ν curves at 5 to 15 K for 2 (Hdc = 0 Oe) (b); plot of ln(τ) versus 1/T for 2 (Hdc = 0 Oe), the solid line represents the best fitting with Raman + Orbach (c); Cole–Cole curves at 5 to 15 K for 2 (Hdc = 0 Oe), the solid lines represent the best fitting with a generalized Debye model [48,49] (d).
Magnetochemistry 11 00058 g006
Magnetochemistry 11 00058 g007
Figure 7. χ” versus T curves for 2 (Hdc = 1500 Oe) (a); χ” versus ν curves at 5 to 15 K for 2 (Hdc = 1500 Oe) (b).
Figure 7. χ” versus T curves for 2 (Hdc = 1500 Oe) (a); χ” versus ν curves at 5 to 15 K for 2 (Hdc = 1500 Oe) (b).
Magnetochemistry 11 00058 g007
Table 1. Selected bond lengths (Å) and angles (°) of 1.
Table 1. Selected bond lengths (Å) and angles (°) of 1.
Dy1–O42.303(6)Dy1–O1 #12.191(6)
Dy1–O32.355(6)Dy1–O22.352(5)
Dy1–O2 #12.385(5)Dy1–O92.360(6)
Dy1–N32.579(7)Dy1–N1 #12.502(7)
Dy2–O52.197(6)Dy2–O82.302(6)
Dy2–O6 #22.340(6)Dy2–O62.387(5)
Dy2–O72.352(6)Dy2–O102.351(6)
Dy2–N102.584(7)Dy2–N82.497(7)
    
O4–Dy1–O371.4(2)O4–Dy1–O9147.9(2)
O3–Dy1–O9140.7(2)Dy1–O2–Dy1 #1112.7(2)
O8–Dy2–O771.4(2)O8–Dy2–O10148.5(2)
O10–Dy2–O7140.0(2)Dy2 #2–O6–Dy2112.6(2)
#1 1 − x, 2 − y, 1 − z; #2 −x, 1 − y, 2 − z.
Table 2. Selected bond lengths (Å) and angles (°) of 2.
Table 2. Selected bond lengths (Å) and angles (°) of 2.
Dy1–O42.326(2)Dy1–O22.176(2)
Dy1–O52.361(2)Dy1–O32.312(2)
Dy1–O3 #32.322(2)Dy1–O62.392(2)
Dy1–N12.509(2)Dy1–N3 #32.541(2)
    
O4–Dy1–O571.04(7)O4–Dy1–O6149.21(8)
O5–Dy1–O6139.50(8)Dy1–O3–Dy1#3113.95(8)
#3 1 − x, 1 − y, 1 − z.
Table 3. Main structural parameters in the Dy2O2 core and nature of the magnetic interactions for some Dy2 SMMs with hydrazine Schiff base ligands.
Table 3. Main structural parameters in the Dy2O2 core and nature of the magnetic interactions for some Dy2 SMMs with hydrazine Schiff base ligands.
ComplexMagnetic InteractionDy⋯Dy (Å)Dy⋯O (Å) aDy⋯Dy (°)Coordination SphereRef.
[Dy2(ovph)2Cl2(MeOH)3]·solferromagnetic3.8642.333112.3, 111.5N2O6, N2O3Cl2[11]
[Dy2(L1)2(NO3)2(CH3OH)2]·solferromagnetic3.9232.327114.9N2O6[12]
Dy2(L2)2(DMF)2(NO3)2ferromagnetic3.8692.319113.0N2O6[32]
Dy2(L2)2(DMF)2(AcO)2ferromagnetic3.9612.348115.1N2O6[32]
[Dy2(TTA)2(L3)2(CH3OH)2]·solferromagnetic3.9922.374114.5N2O6[33]
[Dy2(tfa)2(L3)2(CH3OH)2]ferromagnetic3.9112.363111.7N2O6[33]
[Dy2(R-L)2(L4)2(DMA)2]ferromagnetic3.8792.380109.4, 108.9N2O6[34]
[Dy2(S-L)2(L5)2(H2O)(MeOH)]·solferromagnetic3.9012.369111.3, 110.4N2O6[35]
[Dy2(D-tfc)2(L6)2(H2O)2]·solferromagnetic3.9022.357111.6, 111.9N2O6[36]
[Dy2(D-tfc)2(L7)2(H2O)2]·solferromagnetic3.8992.352111.9, 112.1N2O6[36]
[Dy2(D-pfc)2(L6)2(DMF)2]ferromagnetic3.9062.333113.4, 113.3N2O6[36]
[Dy2(D-pfc)2(L7)2(H2O)2]·solferromagnetic3.9182.353113.2, 112.2N2O6[36]
[Dy2(LSchiff-1)2(DMF)2(dpp)2]·solferromagnetic3.942, 3.9322.366112.7, 112.6N2O6this work
[Dy2(LSchiff-2)2(DMF)2(dpp)2]·solferromagnetic3.8852.317113.95N2O6this work
[Dy2(NO3)2(H2L8)2]·NO3·sol 3.9762.414110.5, 111.0N3O6[42]
a Average values. H2ovph: pyridine-2-carboxylic acid [(2-hydroxy-3-methoxyphenyl)methylene] hydrazide; H2L1: N′-((2-hydroxy-1-naphthyl)methylene) picolinohydrazide; H2L2: N’-(2-hydroxy-5-methylphenyl)-pyrazine-2-carbohydrazide; H2L3: N’-(2-hydroxy-5-methylphenyl)-pyrazine-2-carbohydrazide; HTTA: 2-thenoyltrifluoroacetone; Htfa: trifluoroacetylacetone; H2L4: (E)-N′-(2-hydroxybenzylidene)-3-aminopyrazine-2-carbohydrazide; R-HL: (R)-(+)-chlocyphos; H2L5: (E)-N′-(5-fluoro-2-hydroxybenzylidene)pyrazine-2-carbohydrazide; S-HL: (S)-5,5′,6,6′,7,7′,8,8′-octahydro-1,1′-bi-2-naphthyl phosphate; H2L6: (E)-N’-(2-hydroxy-3-methoxybenzylidene)pyrazine-2-carbohydrazide; D-Htfc: (+)-3-trifluoroacetyl camphor; H2L7: (E)-N’-(2-hydroxy-3-methoxybenzylidene)nicotinohydrazide; D-Hpfc: 3-(perfluorobutyryl)-(+)/(−)-camphor; H4L8: 6-((bis(2-hydroxyethyl)amino)-N′-(2hydroxybenzylidene)picolinohydrazide).
Table 4. Crystal data and structural refinement parameters for 1 and 2.
Table 4. Crystal data and structural refinement parameters for 1 and 2.
12
formulaC57.5H47.5Cl2Dy2N14.5O10.5C66H68Dy2N14O14
FW1505.501606.34
crystal systemtriclinicmonoclinic
space groupP-1P21/c
a [Å]13.6737(3)13.5044(2)
b [Å]15.5510(4)16.6323(2)
c [Å]17.1825(4)15.5855(2)
α [°]71.194(2)90
β [°]68.498(2)107.308(2)
γ [°]67.717(2)90
V [Å3]3073.36(14)3342.13(8)
Z22
ρcalc [g cm−3]1.6271.596
μ [mm−1]2.5692.294
T [K]170170
λ [Å]0.710730.71073
reflections collected73,96847,513
unique reflections10,1255572
observed reflections89495247
parameters808438
GoF1.1811.075
R1 [I ≥ 2σ (I)]0.06050.0242
WR2 [I ≥ 2σ (I)]0.19330.0639
CCDC24540312454030
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Liu, C.-M. Two Dy2 Zero-Field Single-Molecule Magnets Derived from Hydrazone Schiff Base-Bridging Ligands and 1,3-Di(2-pyridyl)-1,3-propanedione. Magnetochemistry 2025, 11, 58. https://doi.org/10.3390/magnetochemistry11070058

AMA Style

Liu C-M. Two Dy2 Zero-Field Single-Molecule Magnets Derived from Hydrazone Schiff Base-Bridging Ligands and 1,3-Di(2-pyridyl)-1,3-propanedione. Magnetochemistry. 2025; 11(7):58. https://doi.org/10.3390/magnetochemistry11070058

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Liu, Cai-Ming. 2025. "Two Dy2 Zero-Field Single-Molecule Magnets Derived from Hydrazone Schiff Base-Bridging Ligands and 1,3-Di(2-pyridyl)-1,3-propanedione" Magnetochemistry 11, no. 7: 58. https://doi.org/10.3390/magnetochemistry11070058

APA Style

Liu, C.-M. (2025). Two Dy2 Zero-Field Single-Molecule Magnets Derived from Hydrazone Schiff Base-Bridging Ligands and 1,3-Di(2-pyridyl)-1,3-propanedione. Magnetochemistry, 11(7), 58. https://doi.org/10.3390/magnetochemistry11070058

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