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Article

A New Family of Heterometallic LnIII[12-MCFeIIIN(shi)-4] Complexes: Syntheses, Structures and Magnetic Properties

by
Tingting Lou
,
Hua Yang
,
Suyuan Zeng
,
Dacheng Li
and
Jianmin Dou
*
Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell Technology, School of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng 252059, China
*
Author to whom correspondence should be addressed.
Crystals 2018, 8(5), 229; https://doi.org/10.3390/cryst8050229
Submission received: 21 April 2018 / Revised: 13 May 2018 / Accepted: 17 May 2018 / Published: 19 May 2018
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Abstract

:
A new family of LnIII [12-Metallacrown-4] compounds of formulas (C5H6N) [LnFe4(shi)4(C6H5COO)4(Py)4]·3.5Py [Ln = EuIII (1); GdIII (2); TbIII (3); DyIII (4); and, H3shi = salicylhydroxamic acid] were obtained through one-pot reactions with H3shi, Fe(NO3)3·9H2O, and, Ln(NO3)3·6H2O as reagents. Single-crystal X-ray analyses show that they are isostructural and have the similar [12-MCFeIII N(shi)-4] core, with four benzoate molecules bridging the central LnIII ion to the ring FeIII ions. The negative charge of the 12-MC-4 metallacrown is balanced by one pyridinium cation, which forms the hydrogen bond with an adjacent solvent pyridine molecule. Magnetic measurements demonstrate antiferromagnetic coupling interactions and field-induced slow magnetic relaxation in complex 4.

1. Introduction

With the rapid development of information technology, it is essential to produce information storage materials with higher storage density and faster response speed. Single molecule magnet (SMM), acting as a separate magnetic domain, behaves potential applications in information storage and quantum computation [1,2,3,4]. The first SMM was reported in 1993 [5], then, such cases have attracted considerable attention from chemists and physicists due to their unique magnetic properties [6,7,8,9]. As we all know, the involved metallic ions for the studies of SMMs mainly consist of paramagnetic three-dimensional (3d) ions, heterometallic 3d-4f ions and homometallic 4f ions. With the high magnetic anisotropy of 3d ions and large spin-orbital coupling of 4f ions, the heterometallic 3d–4f complexes have represented extreme properties in magnetic investigations. So far, the most studied 3d–4f complexes include heterometallic Mn-Ln, Cu-Ln [10,11], Zn-Ln [12], and Co-Ln [13,14], SMMs, and a few Fe-Ln SMMs. Furthermore, the survey of heterometallic Fe-Ln complexes only shows Fe2Ln2 and Fe3LnO2 butterfly core [15,16], Fe2Ln triangular system [17], and Fe4Dy2 S-shape [18] structural frameworks. Few cyclic Fe-Ln compounds have been documented [19,20]. Therefore, it is interesting to investigate the heterometallic Fe-Ln complexes with cyclic structures and to explore their magnetic properties.
Metallacrowns (MCs), which are a type of metallic macrocyclic polynuclear complexes, are usually regarded as metal ions and nitrogen atoms instead of methylene carbons of organic crowns [21,22]. The first MC with the formula represented by {[VO (shi) (MeOH)]3(9-MC-3) shi = salicylhydroxamic acid} was reported in 1989 [23], since then, a great deal of metallacrowns with different structural types from 9-MC-3 to 60-MC-20 have been explored [24,25,26,27,28]. The ring metal ions for these MCs contain homogeneous 3d ions or heterometallic 3d-4f ions. For 3d-4f MCs, they embody Mn-LnIII [12-MC-4], Mn-LnIII [14-MC-5], and Cu-LnIII [15-MC-5] structural types [29,30]. Recently, a series of Zn-Ln MCs also have been documented with two [12-MCZn-4] MC units capping a LnIII [24-MCZn-8] unit to form a sandwich motif and possess near-infrared luminescent [31]. Nevertheless, few MCs consisting of Fe-Ln ions have been found, except that several homometallic [9-MCFeIII-3], [18-MCFeIII-6] MCs, and a family of 18-MC-6 azametallacrowns have exhibited charming structures and magnetic properties [24,32,33,34]. Due to the high magnetic anisotropy and large spin-orbital coupling of LnIII ions, as well as high-spin FeIII with S = 5/2 spin state presenting Spin Crossover (SCO) [35,36,37,38], it is meaningful to explore macrocyclic polynuclear complexes with Fe-Ln MCs structures and magnetic properties.
In the previous research, only a family of FeIII-Ln [18-MC-6] MCs [34] have been published. In order to further expand Fe-Ln MCs structural types and to study their magnetic properties, we synthesized a series of new LnIII [12-MCFeIIIN(shi)-4] [Ln = EuIII (1), GdIII (2), TbIII (3), DyIII (4)] complexes through the reactions of salicylhydroxamic acid (H3shi) and the corresponding metal salts. Their structures were characterized by X-ray single diffraction and the magnetic properties were also explored in detail.

2. Materials and Methods

2.1. Materials

Salicylhydroxamic acid, Fe(NO3)3·9H2O, Ln(NO3)3·6H2O, sodium benzoate, CH3OH, and pyridine. All of the reagents were commercially available without further purification.

2.2. Physical Methods

Elemental analyses for carbon, hydrogen, and nitrogen were tested by Elementar Vario EL analyzer (Elementar, Langenselbold, Germany). The IR spectra were measured on a Perkin-Elmer Spectrum (ThermoNicolet Corporation, Madison, WI, USA) with samples being prepared as KBr pellets. The XRD patterns were recorded using a XD-3 system with a CuKa radiation (General Analysis Corporation, Beijing, China) source (λ = 1.54 Å) at 36 keV and 20 mA in the 2θ range between 5° and 50°, at 0.04 steps every 4 s. Magnetic measurements on crystalline samples were carried out in the temperature range of 1.8–300 K under an applied field of 1000 Oe by using a Quantum Design MPMS-XL7 SQUID magnetometer (Quantum Design, San Diego, CA, USA). AC susceptibilities were investigated in a zero-applied dc field and 2000 Oe dc field for 1–3 and 1000 Oe dc field for 4, with oscillating frequencies of 1–999 Hz.

2.3. Syntheses

2.3.1. (C5H6N)[EuFe4(shi)4(C6H5COO)4(Py)4]·3.5Py (1)

Salicylhydroxamic acid (H3shi) (0.2 mmol), Fe(NO3)3·9H2O (0.2 mmol), Eu(NO3)3·6H2O (0.05 mmol), and sodium benzoate (0.6 mmol) were dissolved in a mixed solution of 20 mL MeOH and 2 mL pyridine, resulting in a clear, black-red solution and then stirred for six hours. The solution was then filtered and the filtrate was placed in a dark cupboard for crystal growth. The black-red single crystals were yielded after 12 days through the slow evaporation of the black-red solution. The yield was 35.0 mg (32.8%, based on Eu). Elemental analysis (%) calcd for C98.5H79.5Fe4EuN12.5O20: C, 55.45; H, 3.76; N, 8.21. Found: C, 55.06; H, 3.36; N, 8.58. IR (KBr), cm−1: 3456 [ν(O-H)], 1597 [ν(C=N)shi], 1564 [asym(CO2)benzoate], 1446 [sym(CO2)benzoato], and 1262 [(N–Oox)shi]. The purity of the single-crystal samples was determined by the powder X-ray diffraction analyses (Figure S1).

2.3.2. (C5H6N)[GdFe4(shi)4(C6H5COO)4(Py)4]·3.5Py (2)

The complex 2 was obtained by the same way for 1 with Gd(NO3)3·6H2O (0.05 mmol) instead of Eu(NO3)3·6H2O. The black-red single crystals were yielded after 10 days through the slow evaporation of the black-red solution. The yield was 37.8 mg (35.4%, based on Gd). Elemental analysis (%) calcd for C98.5H79.5Fe4GdN12.5O20: C, 55.31; H, 3.75; N, 8.19. Found: C, 55.04; H, 3.35; N, 8.52. IR (KBr), cm−1: 3460 [ν(O-H)], 1597 [ν(C=N)shi], 1563 [asym(CO2)benzoate], 1446 [sym(CO2)benzoato], and 1262 [(N–Oox)shi]. The purity of the single-crystal samples was determined by the powder X-ray diffraction analyses (Figure S1).

2.3.3. (C5H6N)[TbFe4(shi)4(C6H5COO)4(Py)4]·3.5Py (3)

The complex 3 was obtained by the same way for 1 with Tb(NO3)3·6H2O (0.05 mmol) instead of Eu(NO3)3·6H2O. The black-red single crystals were yielded after 13 days through the slow evaporation of the black-red solution. The yield was 45.4 mg (42.4%, based on Tb). Elemental analysis (%) calcd for C98.5H79.5Fe4TbN12.5O20: C, 55.27; H, 3.74; N, 8.18. Found: C, 55.63; H, 3.43; N, 8.45. IR (KBr), cm−1: 3448 [ν(O-H)], 1597 [ν(C=N)shi], 1564 [asym(CO2)benzoate], 1447 [sym(CO2)benzoato], and 1262 [(N–Oox)shi]. The purity of the single-crystal samples was determined by the powder X-ray diffraction analyses (Figure S1).

2.3.4. (C5H6N)[DyFe4(shi)4(C6H5COO)4(Py)4]·3.5Py (4)

The complex 2 was obtained by the same way for 1 with Dy(NO3)3·6H2O (0.05 mmol) instead of Eu(NO3)3·6H2O. The black-red single crystals were yielded after 15 days through the slow evaporation of the black-red solution. The yield was 40.3 mg (37.6%, based on Dy). Elemental analysis (%) calcd for C98.5H79.5Fe4DyN12.5O20: C, 55.18; H, 3.74; N, 8.17. Found: C, 55.56; H, 3.42; N, 8.52. IR (KBr), cm−1: 3456 [ν(O–H)], 1597 [ν(C=N)shi], 1564 [asym(CO2)benzoate], 1446 [sym(CO2)benzoato], and 1262 [(N–Oox)shi]. The purity of the single-crystal samples was determined by the powder X-ray diffraction analyses (Figure S1).

2.4. X-ray Crystallography

Single-crystal X-ray diffraction data for compounds 1–4 were collected on a Bruker Smart CCD area-detector diffractometer (Bruker AXS Inc., Madison, WI, USA, MoKα, λ = 0.71073 Å) by ω-scan mode operating at 298 K. The program SAINT (version 2014/7) was used for the integration of the diffraction profiles and semiempirical absorption corrections were applied using SADABS (version 2.03). All of the structures were solved by direct methods using the SHELXS (version 2014/7) program of the SHELXTL (version 2014/7) package, and were refined by full-matrix least-squares methods with SHELXL [39]. Further details for crystallography are listed in Table 1.
CCDC 1582199, 1582197, 1582195 and 1582194 contain the supplementary crystallographic data for 1–4. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44-1223-336-033; or e-mail: [email protected].

3. Results and Dissucion

3.1. Description of Crystal Structures

Single-crystal X-ray structural analyses indicate that 1–4 are isostructural heterometallic compounds. The molecular structure of complexes 1–4 are shown in Figure 1a–d. The complex 4 is described as a representative example in detail. It crystallizes in the monoclinic space group P21/n. The asymmetrical unit includes a representative 12-MCFeIIIshi-4 structural framework, which is composed of four FeІІІ ions, four deprotonated shi3- ligands, four benzoate ligands, four dative pyridine molecules, and one DyІІІ ion. The oxidation states of four Fe ions were determined through the bond lengths, charge balance, and the BVS calculations with the values, as shown in Table S1. The Fe 2p XP spectras of a monolayer of complexes 1–4 further prove the the oxydation state of Fe ions [40] (Figure S3, Table S5). Each FeІІІ ion is six-coordinated with N2O4 atoms from carbonyl oxygen, oxime oxygen, hydroxyl oxygen, oxime nitrogen, pyridyl nitrogen, and benzoate oxygen, respectively. Further, each fully deprotonated shi3- ligand links two adjacent FeIII ions through their oxime oxygen and oxime nitrogen to form the N-O bridgings between these FeIII ions. Thus, four FeIII ions and four shi3- ligands are held together to form a 12-MC-4 MC core with the ring presenting Fe–N–O repeat unit. For these four shi3- ligands, an obvious difference is that three ligands are located in the MC plane, and the fourth ligand is nearly perpendicular to the MC plane. It may be attributed to the steric hindrance to make the fourth ligand distortion. The dihedral angle between the twisted ligand and the MC plane is 81.8(9)°.
Interestingly, one DyІІІ ion that is encapsulated in the cavity of 12-MC-4 ring. DyIII ion is located in eight coordination environment with the coordination atoms from MC ring four oxygen atoms and four –Obz carbonyl oxygen atoms (Figure S2a). For the coordination configuration of DyIII ions, the parameter α is usually used to depict the elongation or the flatness in a square antiprism. α is calculated through the S8 axis of the square antiprism, and the central atom ligand bond, in the meantime, it is also can be defined as γ/2, where γ is the angle between opposite ligands within one hemisphere. For complex 4, the values of γ angles for Dy1 are 119.701(195)° (O14-Dy1-O11), 117.036(199)° (O16-Dy1-O13), 108.037(189)° (O5-Dy1-O20), and 111.726(196)° (O3-Dy1-O8), respectively. The α angles of 59.851° (O14, O11) and 58.518° (O16, O13) in the hemisphere (O14, O13, O11, and O16), as well as 54.019° (O5, O20) and 55.863° (O3, O8) in the hemisphere (O8, O5, O3, and O20) are slightly deviated from the theoretical value (57.16°) by 2.691, 1.358, 3.141, and 1.297°, respectively. Complexes 1–3 also possess eight-coordination with a distorted square antiprism geometry (Figure S2b–d), and the angles are shown in Table S2. The encapsulated DyIII ion and ring FeIII ions are further bridged through two oxygen atoms of –Obz groups with the bond lengths of Fe–O and Dy–O in the ranges 2.361(6)–2.475(5) and 1.901(6)–2.041(6) Å, and the angles of Fe−O−Dy in the range 119.2(2)–123.2(2)°, respectively.
It is worthily noted that the 12-MC-4 MC unit displays the negative valence with its charge balanced by one pyridinium cation, where the pyridine nitrogen is protonated. The angle of C–N–C is 138.748(254)°, which is larger than that of the parent pyridine complex, which results in the occurrence of the protonation on this site [41,42,43]. Meanwhile, the hydrogen bond interaction is formed between the pyridinium cation and an adjacent pyridine molecule, which is also reported in [12-MCGaIIIN(shi)-4] [44].
Complexes 1–3 have the similar structural configuration with 4 and the difference is discussed. The deviation distances of LnIII ions to the oxime oxygen mean plane (OoxMP) and to the FeIII mean plane (FeMP) are shown in Table 2. From the data, we can see that, as the radius of LnIII ions decrease, the LnIII are approach the plane much more. The similar tendency was also observed in the reported 12-MCMnIII(N)shi-4 [45]. The distances between Ln-O and the distortion angles of benzoate for these four complexes are slightly different, further details are shown in Tables S3 and S4.

3.2. Magnetic Properties

The variable temperature magnetic susceptibilities of the complexes 1–4 were determined in the temperature range of 1.8–300 K and an applied field of 0.1 T. The χMT versus T plots are shown in Figure 2. The values of χMT for complexes 1–4 are 16.20 (1), 21.27 (2), 26.01 (3), and 29.22 (4) cm3 mol−1 K at 300 K, respectively, which are lower than expected values of non-interacting four FeІІІ ions (d5, S = 5/2, g = 2) and one LnІІІ [EuIII, 7F0; GdIII, 8S7/2, g = 2; TbIII, 7F6, g = 3/2; DyIII, 6H15/2, g = 4/3] ion of 19.00 (1), 25.21 (2), 29.15 (3), and 31.50 (4) cm3 mol−1 K. With the temperature reducing, the χMT values decrease gradually to 0.18 (1), 7.90 (2), 8.62 (3), and 11.01 (4) cm3 mol−1 K at 1.8 K, respectively (Table 3), manifesting the antiferromagnetic coupling in the complexes. The fitting of the Curie-Weiss law for the high-temperature χMT values resulted in different θ values, with −131.96 K, −59.83 K, −43.72 K, and −40.00 K for complexes 1–4, respectively.
Similar to other reported Fe-Ln complexes, the magnetic behavior of this series of compounds is also related to the FeIII–FeIII, FeIII–LnIII, and the intrinsic magnetic properties of the LnIII ions. For complex 1, including the EuIII ion, we may try to explore the magnetic interaction mode between metal ions, while for other complexes it is difficult to define. The ground state of EuIII ion is 7F0 and the configuration is 4f6 (7F0, S = 3, L = 3, J = 0). At a low temperature, only the infinitesimal excited states mixing into 7F0 [46] occupied the nonmagnetic ground level. Thus, the magnetic properties of complex 1 at a low temperature are mainly caused by the exchange interaction between FeIII ions. This indicates that the EuIII ion can be deemed to be the diamagnetic ion at low temperature. The extrapolation of χMT value to 0 K is approaching zero, suggesting that the ground state spin of 1 can be recognized to be S = 0. Therefore, we can come to a conclusion that the FeIII–FeIII interaction mainly lead to the antiferromagnetic behavior of 1. Complexes 2–4 also present antiferromagnetic behavior, but the nonzero ground-state spins may attributed to uncanceled spins between the Fe4 unit and LnIII ion. However, owing to the complexity magnetic coupling interactions between FeІІІ-LnІІІ (GdIII, TbIII, DyIII) and the intrinsic magnetism of LnIII ions, it is very difficult to obtain the appropriate coupling constants for complexes 2–4.
The magnetization of the complexes 1–4 was measured in the 1–7 T magnetic fields and 1.8–8 K temperature range. As shown in Figures S11–S14, the magnetization increases rapidly in the low magnetic field, and then a linear increase without clear saturation at 7 T, with values of 2.52 μB for 1, 6.42 μB for 2, 5.96 μB for 3, and 6.92 μB for 4 at 1.8 K. The reduced magnetization (M/NμB−H/T) curves show the non-superposition, suggesting the magnetic anisotropy of metal ions in the molecules and the lack of a well-defined ground state.
In order to further study the magnetic relaxation dynamics of 1–4, the ac susceptibilities were carried out at frequencies in the range of 1–999 Hz and in the temperature range of 1.8–15 K under zero-applied dc field and 2000 Oe dc field for complexes 1–3 and 1000 Oe dc field for complex 4, with a 2.0 Oe ac field oscillating. Complexes 1–4 exhibit similar curves for the in-phase (χ′M) and out-of-phase (χ″M) under zero-applied dc field, showing the absence of SMM behavior (Figures S4, S6, S8, and S10). When a 2000 Oe dc field was applied for 1–3 and a 1000 Oe dc field was used for 4, the out-of-phase (χ″M) signals of complexes 1–3 represent absence of frequency-dependent (Figures S5, S7 and S9), however, complex 4 demonstrates obvious frequency-dependent, revealing the field-induced slow magnetic relaxation (Figure 3). Owing to the absence of maximum value of χ″M for 4, the energy barrier (∆Eeff) and preexponential factor (τ0) can only be calculated by the Debye equation: ln (χ″/χ′) = ln (ωτ0) + ∆Eeff/kB T [16,47] (Figure 4). The perfect fitting data are shown in Table 4. The characteristic times is 10−6 s for complex 4, values that are in agreement with the observed preexponential factors and effective energy barriers for LnIII-containing SMMs [34]. In our Fe4Ln analogues, however, only the Fe4Dy complex represented the magnetic dependence upon the frequencies at 1000 Oe dc field. May be the intrinsic properties of trivalent LnIII ions can account for the phenomenon. In most of the coordination environment, DyIII, as the Kramers ion, could always keep the doubly degenerate ground state under the magnetic field. Nevertheless, the non-Kramers ion, TbIII, needs strict axial crystal-field symmetry. Furthermore, the EuIII ion has a ground state of J = 0, while the GdIII ion is isotropic.

4. Conclusions

We prepared a new family of heterometallic LnІІІ [12-MCFeIIIN(shi)-4] (Ln = EuIII, GdIII, TbIII, DyIII) MCs through the one-pot reactions of H3Shi ligand with the corresponding iron and lanthanide metal salts. The 12-MC-4 structural unit exhibits a monovalent negative ion with the charge being balanced by one pyridinium cation. The arched structure of the 12-MCFeIIIN(shi)-4 is related to the radius of LnIII ions, as the LnIII ions’ radius decrease, the complex has a less domed structure. The magnetic behavior of the family of compounds was discussed in detail, including the FeIII–FeIII and FeIII–LnIII interactions. FeIII–FeIII interaction within all of the compounds may be antiferromagnetic. The nonzero ground-state spins may attributed to uncanceled spins between the LnIII and FeIII ions. All of the compounds reveal antiferromagnetic behavior and the Fe4Dy analogue with high anisotropy and large spin shows slow magnetization relaxation at a dc field of 1000 Oe. From the experiment, we can draw a conclusion that the choice of LnIII is important for the SMM properties.

Supplementary Materials

The following are available online at https://www.mdpi.com/2073-4352/8/5/229/s1, Figure S1: The experimental XRD pattern of samples and the simulated XRD pattern of single crystal X-ray diffraction data for complexes 1–4, Figure S2: Distorted square-antiprismatic geometries around Dy1(a), Eu1(b), Gd1(c), Tb1(d), Figure S3: Fe 2p XP spectras of complexes 1 (a), 2 (b), 3 (c), 4 (d) in monolayers, Figure S4: Temperature dependence of the in-phase (χ'M) and out-of phase (χ''M) ac susceptibility signals of complex 1 measured under 2.0 Oe field with a 0 dc field, Figure S5: Temperature dependence of the in-phase (χ'M) and out-of phase (χ''M) ac susceptibility signals of complex 1 measured under 2.0 Oe field with a 2000 Oe dc field, Figure S6: Temperature dependence of the in-phase (χ'M) and out-of phase (χ''M) ac susceptibility signals of complex 2 measured under 2.0 Oe field with a 0 dc field, Figure S7: Temperature dependence of the in-phase (χ'M) and out-of phase (χ''M) ac susceptibility signals of complex 2 measured under 2.0 Oe field with a 2000 Oe dc field, Figure S8: Temperature dependence of the in-phase (χ'M) and out-of phase (χ''M) ac susceptibility signals of complex 3 measured under 2.0 Oe field with a 0 Oe dc field, Figure S9: Temperature dependence of the in-phase (χ'M) and out-of phase (χ''M) ac susceptibility signals of complex 3 measured under 2.0 Oe field with a 2000 Oe dc field, Figure S10: Temperature dependence of the in-phase (χ'M) and out-of phase (χ''M) ac susceptibility signals of complex 4 measured under 2.0 Oe field with a 0 Oe dc field, Figure S11: Plots of isothermal magnetization M vs. H for complex 1 at 1.8–8 K (left). Plots of magnetization M vs. H/T for complex 1 at 1–7 T (right), Figure S12: Plots of isothermal magnetization M vs. H for complex 2 at 1.8–8 K (left). Plots of magnetization M vs. H/T for complex 2 at 1–7 T (right), Figure S13: Plots of isothermal magnetization M vs. H for complex 3 at 1.8–8 K (left). Plots of magnetization M vs. H/T for complex 3 at 1–7 T (right), Figure S14: Plots of isothermal magnetization M vs. H for complex 4 at 1.8–8 K (left). Plots of magnetization M vs. H/T for complex 4 at 1–7 T (right), Table S1: The BVS calculations for complexes 1–4, Table S2: Selected bond angles for complexes 1−3, Table S3: The distances between Ln-O for complexes 1−4, Table S4: The distortion angles of benzoate for complexes 1−4, Table S5: Fit parameters for the Fe 2p XP spectra of complexes 1–4.

Author Contributions

T.L., J.D. and D.L. conceived and designed the experiments; T.L. performed the experiments; S.Z. measured properties; T.L. and H.Y. analyzed the data; T.L. wrote the manuscript.

Funding

This work was financially supported from the National Natural Science Foundation of China (Grants 21671093 and 21271097).

Conflicts of Interest

The authors declare no conflict of interest.

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Crystals 08 00229 g001 550
Figure 1. Overall molecular structure for complex 1 (a), complex 2 (b), complex 3 (c), and complex 4 (d) (Some hydrogen atoms have been omitted for clarity).
Figure 1. Overall molecular structure for complex 1 (a), complex 2 (b), complex 3 (c), and complex 4 (d) (Some hydrogen atoms have been omitted for clarity).
Crystals 08 00229 g001
Crystals 08 00229 g002 550
Figure 2. χMT vs. T plots for complexes 1–4 in an applied 1000 Oe dc field.
Figure 2. χMT vs. T plots for complexes 1–4 in an applied 1000 Oe dc field.
Crystals 08 00229 g002
Crystals 08 00229 g003 550
Figure 3. (a) Temperature dependence of the in-phase (χ′M) of ac susceptibility signals for complex 4 measured under a 1000 Oe dc field. (b) Temperature dependence of the out-of phase (χ′′M) of ac susceptibility signals for complex 4 measured under a 1000 Oe dc field.
Figure 3. (a) Temperature dependence of the in-phase (χ′M) of ac susceptibility signals for complex 4 measured under a 1000 Oe dc field. (b) Temperature dependence of the out-of phase (χ′′M) of ac susceptibility signals for complex 4 measured under a 1000 Oe dc field.
Crystals 08 00229 g003
Crystals 08 00229 g004 550
Figure 4. Magnetization relaxation time ln(χ′′/χ′) vs T −1 plots for complex 4.
Figure 4. Magnetization relaxation time ln(χ′′/χ′) vs T −1 plots for complex 4.
Crystals 08 00229 g004
Table
Table 1. Crystal data and structure refinement for complexes 1–4.
Table 1. Crystal data and structure refinement for complexes 1–4.
1234
Empirical formulaC98.5H79.5Fe4
N12.5O20Eu		C98.5H79.5Fe4
N12.5O20Gd		C98.5H79.5Fe4
N12.5O20Tb		C98.5H79.5Fe4
N12.5O20Dy
Formula weight2133.602138.892140.572144.15
T(K)298(2)298(2)298(2)298(2)
Crystal systemMonoclinicMonoclinicMonoclinicMonoclinic
Space groupP2(1)/nP2(1)/nP2(1)/nP2(1)/n
a(Å)14.3022(13)14.2222(13)14.2903(13)14.3011(13)
b(Å)34.152(3) 33.248(3)34.258(3)34.231(3)
c(Å)19.4743(17)19.3213(17)19.4615(16)19.5141(17)
α(°)90909090
β(°)106.772(2) 105.913(3)106.756(3)106.873(3)
γ(°)90909090
V(Å3)9107.6(14)8786.0(13)9123.1(14)9141.7(14)
Z4444
Dc (Mg·m−3)1.5561.6171.5581.558
μ (mm−1)1.3811.4721.4661.507
Data/parameters16,024/10,07415,469/10,47616,064/10,25616,090/10,256
Rint0.06470.06640.06750.0724
GOOF (F2)1.0201.0821.0671.047
R1 [I > 2σ(I)]0.05940.06810.06770.0706
wR2 (all data)0.10460.15140.15130.1846
Table
Table 2. The deviation distance from LnIII ions to OoxMP and FeMP.
Table 2. The deviation distance from LnIII ions to OoxMP and FeMP.
CompoundLnIII-OoxMP distance (Å)LnIII-FeMP distance (Å)
Fe4Eu (1)1.3943 (3)1.7826 (3)
Fe4Gd (2)1.3875 (4)1.7728 (4)
Fe4Tb (3)1.3867 (4)1.7589 (4)
Fe4Dy (4)1.3864 (4)1.7505 (4)
Table
Table 3. Expected and measured χMT values for 1–4.
Table 3. Expected and measured χMT values for 1–4.
CompoundExpectedMeasuredMeasured
spin onlyvaluevalue
valueat 300 Kat 1.8 K
(cm3 mol−1 K)(cm3 mol−1 K)(cm3 mol−1 K)
Fe4Eu (1)1916.20.18
Fe4Gd (2)25.2121.277.9
Fe4Tb (3)29.1526.018.62
Fe4Dy (4)31.529.2211.01
Table
Table 4. Measured ∆Eeff/kB and τ0 values for complex 4.
Table 4. Measured ∆Eeff/kB and τ0 values for complex 4.
Complex 4
Frequency∆Eeff/kBτ0
(Hz)(k)(s)
1004.5417.4 × 10−6
3204.499.10 × 10−6
7704.554.64 × 10−6

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Lou, T.; Yang, H.; Zeng, S.; Li, D.; Dou, J. A New Family of Heterometallic LnIII[12-MCFeIIIN(shi)-4] Complexes: Syntheses, Structures and Magnetic Properties. Crystals 2018, 8, 229. https://doi.org/10.3390/cryst8050229

AMA Style

Lou T, Yang H, Zeng S, Li D, Dou J. A New Family of Heterometallic LnIII[12-MCFeIIIN(shi)-4] Complexes: Syntheses, Structures and Magnetic Properties. Crystals. 2018; 8(5):229. https://doi.org/10.3390/cryst8050229

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Lou, Tingting, Hua Yang, Suyuan Zeng, Dacheng Li, and Jianmin Dou. 2018. "A New Family of Heterometallic LnIII[12-MCFeIIIN(shi)-4] Complexes: Syntheses, Structures and Magnetic Properties" Crystals 8, no. 5: 229. https://doi.org/10.3390/cryst8050229

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