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Article

Nitronyl Nitroxide Biradical-Based Binuclear Lanthanide Complexes: Structure and Magnetic Properties

by
Lu Xi
,
Jing Han
,
Xiaohui Huang
and
Licun Li
*
Department of Chemistry, Key Laboratory of Advanced Energy Materials Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China
*
Author to whom correspondence should be addressed.
Magnetochemistry 2020, 6(4), 48; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry6040048
Submission received: 7 September 2020 / Revised: 30 September 2020 / Accepted: 1 October 2020 / Published: 3 October 2020
(This article belongs to the Special Issue From Magnetic Anisotropy to Molecular Magnets: Theory and Experiments)
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Abstract

:
Employing a new nitronyl nitroxide biradical NITPhPzbis(NITPhPzbis = 5-(1-pyrazolyl)-1,3-bis(1’-oxyl-3’-oxido-4’,4’,5’,5’-tetramethyl-4,5-hydro-1H-imidazol-2-yl)benzene), a series of 2p-4f complexes [Ln2(hfac)6(H2O)(NITPhPzbis)] (LnIII = Gd1, Tb2, Dy3; hfac = hexafluoroacetylacetonate) were successfully synthesized. In complexes 1–3, the designed biradical NITPhPzbis coordinates with two LnIII ions in chelating and bridging modes to form a four-spin binuclear structure. Direct-current magnetic study of Gd analogue indicates that ferromagnetic exchange exists between the Gd ion and the radical while antiferromagnetic coupling dominates between two mono-radicals. Dynamic magnetic data show that the χ” signals of complex 3 exhibit frequency dependence under zero field, demonstrating slow magnetic relaxation behavior in complex 3. And the estimated values of Ueff and τ0 are about 8.4 K and 9.1 × 10−8 s, respectively.

Graphical Abstract

1. Introduction

In recent years, radical-lanthanide architectures have been appealing candidates for molecular nanomagnets (i.e., single-molecule magnets (SMMs) and single-chain magnets (SCMs)) due to a beneficial combination of strong magnetic anisotropy originated from lanthanide ion and effective magnetic exchange between 4f ion and radical [1,2,3,4,5,6,7,8,9,10,11,12]. Using this intriguing strategy, some remarkable results have been obtained, e.g., a N23- radical-bridged binuclear Tb-SMM with a blocking temperature of 20 K [13]; the radical-bridged trinuclear Dy SMMs Cp*6Dy3(μ3-HAN)(HAN = hexaazatrinaphthylene; Cp* = pentamethylcyclopentadienyl) displaying obvious hysteresis loop below 3.5 K [14]. In 2018, K. R. Dunbar et al., reported the first metallacycle [Dy3(hfac)6(bptz−•)3](bptz = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine; hfac = hexafluoroacetylacetonate) exhibiting temperature-dependent out-of-phase (χ”) signals in the high-frequency range [15]. Noticeable, most of radical-Ln based molecular nanomagnets are constructed using mono-radicals [3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22], and the employments of biradicals are less common [23,24,25,26,27,28]. Nitronyl nitroxide biradical-Ln approach, one hand, can result in interesting spin topology in which the unique magnetic behavior could be observed. On the other hand, intramolecular magnetic coupling may be tuned through the choice of the suitable conjugated spacer of the biradical [29]. Nitronyl nitroxide biradical-Ln strategy provides new chances for designing molecular nanomagnets. Until now, only a handful of nitronyl nitroxide biradical-Ln compounds with slow relaxation of magnetization have been reported [25,26,27,28] due to the inherent difficulties encountered during the biradical preparation [30,31]. Very recently, we reported a series of nitronyl nitroxide biradical bridged tetranuclear lanthanide complexes by means of a nitronyl nitroxide biradical with one flexible pyridine group [28], some of which are SMMs. Following this work, herein we designed a new nitronyl nitroxide biradical, namely, 5-(1-pyrazolyl)-1,3-bis(1’-oxyl-3’-oxido-4’,4’,5’,5’-tetramethyl-4,5-hydro-1H-imidazol-2-yl)benzene (NITPhPzbis, Scheme 1). Utilizing this biradical, a family of nitronyl nitroxide biradical bridged binuclear lanthanide complexes [Ln2(hfac)6(H2O) (NITPhPzbis)] (LnIII = Gd 1, Tb 2, Dy 3) were fabricated. The magnetic investigations show that the exchange coupling between GdIII ion and the coordinated NO group is ferromagnetic. Moreover, the slow magnetic relaxation was found in Dy analogue.

2. Results and Discussion

2.1. Synthetic Aspect and Crystal Structures

The specific synthesis process of NITPhPzbis is shown in Scheme S1. Three binuclear Ln-based complexes were successfully prepared by using NITPhPzbis. The elemental analysis results of complexes 1–3 match well with their theoretical values. To further determine the phase purity of the crystal samples, PXRD tests on complexes 1–3 were conducted (Figure S1). It can be seen that the experimental spectra are consistent with the simulated spectrum of complex 3, which provides an important guarantee for the next study of magnetic property. Figure S2 presents the IR spectra of 1–3. The peaks observed at about 1605 cm−1, 1506 cm−1, and 1353 cm−1 are severally attributed to the C=C, C=N, and N−O stretching in the NITPhPzbis ligand while the absorption peaks at about 1648 cm–1 (νC=O), 800 cm−1 (δC-O), 1247 cm−1, 1131 cm−1 (νC-F), and 658 cm−1 (δC-F) originate from the co-ligand hfac−. The weak absorption bands at about 3575cm−1 are due to the coordinated H2O molecules.
Crystallographic study proves that complexes 1–3 are isomorphous (Figure 1 and Figures S3 and S4) and all belong to the triclinic Pī system. The crystallographic data and refinement parameters for 1–3 are included in Table 1, and the important parameters are presented in Table 2. Here, the structure of complex 1 will be a representative for description. As shown in Figure 1a, the NITPhPzbis ligand chelates one Gd(hfac)3 unit through its two adjacent NO groups, and coordinates with another Gd(hfac)3 unit through another NO group to form a four-spin binuclear structure. Both Gd1 and Gd2 are in eight-coordinated environment, and the eighth coordination sphere of Gd2 is completed with a H2O molecule. There is weak hydrogen bond interaction between the pyrazolyl-N (N6) and the coordinated water molecule in which the distance of O17water(H-donor)⋅⋅⋅N6pyrazol(H-acceptor) is 2.811 Å and the angle of O17water-H⋅⋅⋅N6pyrazolis 148.91°. According to SHAPE analysis [32,33], the coordination geometry of Gd1 is C2v symmetry while that of Gd2 is D2d (Figure 1b, Table S2). In complex 1, the bond lengths of the two Gd1–Orad bonds are 2.383(8) Å and 2.472(7) Å, respectively, and the distance of Gd2–Orad is 2.454(7) Å. The bond lengths here are consistent with those existed in other nitronyl nitroxide biradical-GdIII complexes [26,27,28]. The length of the Gd–Ohfac bond ranges from 2.343(9) to 2.412(7) Å. The bond distance of Gd2–OH2O is 2.378(7) Å. The Gd1–O–N–C torsion angles are 61.3(16)° and −58.5(17)°, respectively, while the Gd2–O–N–C torsion angle is −64.8(14)°. The two dihedral angles between benzene ring and the ON–C–NO of mono-radicals are 37.7(5)° and 31.4(4)° while the dihedral angle formed by pyrazole ring and benzene ring is 30.5(4)°. In the binuclear structure of 1, the distance between the adjacent Gd1 and Gd2 is 8.351 Å. Figure 2 shows the crystal packing diagram of 1. The closest separation between intermolecular GdIII ions is 6.265 Å, and the shortest distance between uncoordinated NO∙∙∙NO is 11.976 Å.

2.2. Magnetic Properties

The dc magnetic susceptibility data of three complexes measured in 1000 Oe magnetic field are shown in Figure 3 and Figure 4. For complex 1, the room temperature value of χMT is 16.99 cm3Kmol−1(Figure 3), slightly higher than the value (16.51 cm3Kmol−1) expected for two GdIII ions (GdIII: 8S7/2, g = 2, C = 7.88 cm3Kmol−1) and two mono-radicals (radical: S = 1/2, g = 2, C = 0.375 cm3Kmol−1) which are magnetically uncorrelated. On lowering the temperature, the χMT value increases steadily to a maximum of 21.35 cm3Kmol−1 at 2K, indicating that ferromagnetic exchange is dominant in the system. The field dependent magnetization curves shown in Figure 3 (inset, 2K). The observed M value of 16.15 Nβ at 7T is in agreement with the theoretical saturation value of 16 Nβ. Based on the molecular structure, magnetic exchange pathway in 1 is shown in Scheme 2, in which J1 is the exchange coupling between the GdIII ion and the ligated NO group and J2 represents the magnetic coupling between two mono-radicals through the GdIII ion and/or m-phenylene ring.
A quantitative analysis has been performed using PHI software [34,35]. The spin Hamiltonian of this system is H = − 2 J 1 ( S ^ G d 2 S ^ r a d 1 + S ^ r a d 1 S ^ G d 1 + S ^ G d 1 S ^ r a d 2 ) − 2 J 2 ( S ^ r a d 1 S ^ r a d 2 ) . The experimental dc susceptibility and magnetization data can be well reproduced and the best fitting parameters are grad = 2.00 (fixed), gGd = 2.02, J1 = 0.74 cm−1, and J2 = −3.24 cm−1. The observed Gd-NO ferromagnetic exchange is expected, which can be ascribed to the electron transfer from π* orbital of the nitronyl nitroxide radical to 6s/5d empty orbitals of GdIII ion [36,37]. The obtained magnitude of J1 is comparable with those in other Gd-nitronyl nitroxide complexes [38]. For J2, two kinds of magnetic pathways are active: one is via the GdIII ion, in which antiferromagnetic coupling is usually generated [39]; the other is through m—phenylene ring, which results in ferromagnetic interaction based on spin polarization mechanism [29] (Scheme 3). Consequently, the observed negative J2 value is the competitive result of these two kinds of magnetic exchange, implying that antiferromagnetic exchange dominates here; this phenomenon has been observed in the similar biradical-Gd compounds [40]. It should be noted that the Gd-NO and NO-NO magnetic interactions observed here are weaker than those in the tetranuclear [Gd4(hfac)12(NITPhO-3Pybis)2] (NITPhO-3Pybis = 5-(3-pyridinyloxy)-1,3-bis(1’-oxyl-3’-oxido-4’,4’,5’,5’-tetramethyl-4,5-hydro-1H-imidazol-2-yl) [28] that contains similar NIT bridged Ln dimer and these can be attributed the differences of Gd–O–N–C torsion angles (61.3(16)°, −58.5(17)° and −64.8(14)° for 1 and −60.2(15)°, 59.5(14)°, and −135.0(13)° for Gd4) in these two complexes which can affect the magnetic exchange between the Gd ion and NO unit [41].
For complexes 2 and 3, the found χMT values at 300K is 24.37 and 28.81 cm3Kmol−1(Figure 4), respectively, which is close to the theoretical values (24.39 cm3Kmol−1 for 2 and 29.09 cm3Kmol−1 for 3) reckoned from an uncoupled system consisting of two LnIII ions (TbIII: 7F6, g = 3/2, C = 11.82 cm3Kmol−1; DyIII: 6H15/2, g = 4/3, C = 14.17 cm3Kmol−1) and two mono-radicals (one radical: S = 1/2, g = 2, C = 0.375 cm3Kmol−1). For both complexes, the value of χMT gradually declines when the temperature is lowered, reaching the minimum values of 22.23 cm3Kmol−1 at 9K for 2 and 27.22 cm3Kmol−1 at 24K for 3, which is most probably governed by the depopulation of the TbIII or DyIII ions Stark levels. Then upon further cooling, the χMT value rapidly increases to the maxima of 22.91 cm3Kmol−1 at 3K for 2 and 30.20 cm3Kmol−1 at 2K for 3, which can be attributed to the ferromagnetic NO-Tb/Dy interaction. For 2, below 3K, the χMT value decreases rapidly and reaches a value of 22.28 cm3Kmol−1 at 2 K. The M versus H curves in the 0–8 T field range at 2K for complexes 2 and 3 are depicted in Figures S7 and S8. The M value is 12.72 Nβ and 12.57 Nβ at 8T for 2 and 3, respectively, which is lower than expected saturation value, suggesting the presence of a significant magnetic anisotropy in the systems [42,43].
Due to the presence of magnetic anisotropic TbIII or DyIII ions in complexes 2 and 3, spin dynamic properties were studied using ac susceptibility measurements under zero dc field. As displayed in Figure S9 and Figure 5, there is no non-zero out-of-phase signal for complex 2 while complex 3 exhibits clear temperature-dependent χ” components, indicating slow relaxation of magnetization behavior in 3. However, no visible peaks of the χ” signals are found for complex 3, which can be attributed to the fast quantum tunneling of magnetization (QTM) [44,45]. Accordingly, frequency-dependent ac magnetic susceptibilities for 3 were investigated at 2 K under dc field range of 200–4900 Oe to determine the optimized external field for suppressing the QTM. As seen, no maxima of χ”(v) components can be observed in the measurement window of our apparatus (Figure S11), suggesting that the QTM cannot be effectively suppressed in the applied dc field, thus the optimum dc field cannot be achieved. To obtain the estimation of reversal barrier (Ueff) and characteristic relaxation time (τ0), the equation l n ( χ ′ ′ / χ ′ ) = l n ( ω τ 0 ) + U e f f / k B T proposed by J. Bartolomé et al. [46,47] was employed. The best fitting afforded Ueff ≈ 8.4 K and τ0 ≈ 9.1 × 10−8 s (Figure 5b) which is in line with the expected characteristic relaxation time 10−6–10−11 s for SMMs [48]. In order to explain the dynamic magnetic behavior of complex 3, magnetic axis directions of Dy1 and Dy2 centers in the binuclear structure were analyzed using the Magellan program [49]. Easy axes on the two DyIII ions are obviously unparallel (Figure 6); an angle of 87.65° is formed between them. This angle is not conducive to the formation of large anisotropy in the system, which may be the reason for the poor magnetic relaxation behavior of 3 [50,51]. As seen, the previously reported tetranuclear [Dy4(hfac)12(NITPhO-3Pybis)2] complex presents superior slow magnetic relaxation behavior than the present [Dy2(hfac)6(H2O)(NITPhPzbis)] complex, which should be attributed to the different coordination environments of Dy ions in the two compounds. The coordination geometries of Dy ions are ascertained as C2v and D2d in [Dy2(hfac)6(H2O)(NITPhPzbis)] while those as C2v and D4d in [Dy4(hfac)12(NITPhO-3Pybis)2]. As known, D4d symmetry is in favor of suppressing QTM effect, thus resulting in different magnetic relaxation [52].

3. Experimental Section

3.1. Materials and Characterizations

The nitronyl nitroxide biradical NITPhPzbis and Ln(hfac)3·2H2O were obtained according to literature methods [53,54,55,56]. The C, N, H content analyses for complexes 1–3 were completed on a Perkin-Elmer 240 elemental analyzer. A Bruker-Vector 22 Spectrometer was employed to collect the IR spectra of all complexes between 4000–400 cm−1. The PAN alytical X’Pert Powder X-ray diffractometer(Cu/Kα radiation, 40 kV × 30 mA) was used to record the PXRD data of 1–3 at room temperature. Magnetic studies of all complexes were conducted on a Quantum Design SQUID VSM and a PPMS magnetometer. Diamagnetic contributions were estimated using Pascal’s constants [57].

3.2. Preparation of [Ln2(hfac)6(H2O)(NITPhPzbis)]

The specific process was as follows: a solution of Ln(hfac)3·2H2O (0.02 mmol) in n—heptane (20 mL) was refluxed with stirring for 6 h. Subsequently, 10 mL CH2Cl2 solution containing 0.0045 g (0.01 mmol) NITPhPzbis ligand was slowly added. After refluxing for 25 min, the mixture was cooled and filtered, and the filtrate was left to evaporate at room temperature. About 5–6 days later, dark-purple block-like crystals were isolated.
[Gd2(hfac)6(H2O)(NITPhPzbis)] (1): C53H38F36Gd2N6O17; Yield 51%; Elem. Anal. (%) found (calcd): C, 31.32 (31.37); N, 4.06 (4.14); H, 1.59 (1.89). FT-IR (cm−1): 3575(w), 1648 (s), 1605 (m), 1506 (m), 1353 (m), 1247 (s), 1131 (s), 952 (m), 896 (m), 870 (m), 800 (s), 761 (m), 658 (s), 583 (s), 544 (m) (Figure S2).
[Tb2(hfac)6(H2O)(NITPhPzbis)] (2): C53H38F36Tb2N6O17; Yield 52%; Elem. Anal. (%) found (calcd): C, 31.30 (31.32); N, 4.07 (4.13); H, 1.49 (1.88). FT-IR (cm−1): 3575(w), 1647 (s), 1605 (m), 1506 (m), 1354 (m), 1249 (s), 1131 (s), 954 (m), 897 (m), 872 (m), 802 (s), 762 (m), 659 (s), 583 (s), 546 (m) (Figure S2).
[Dy2(hfac)6(H2O)(NITPhPzbis)] (3): C53H38F36Dy2N6O17; Yield 54%; Elem. Anal. (%) found (calcd): C, 31.37 (31.21); N, 4.01 (4.12); H, 2.21 (1.88). FT-IR(cm−1): 3575(w), 1648 (s), 1606 (m), 1505 (m), 1354 (m), 1248 (s), 1130 (s), 952 (m), 896 (m), 871 (m), 800 (s), 761 (m), 658 (s), 584 (s), 545 (m) (Figure S2).

3.3. X-ray Crystallography

Crystal diffraction data of 1–3 were collected on a Rigaku Saturn CCD X-ray diffractometer (Mo-Kα, λ = 0.71073 Å) with a scanning mode of ω-φ and a test temperature of 113(2) K. Direct methods were utilized to solve crystal structures of 1–3 using SHELXS-2014 and SHELXL-2014 [58,59]. All non-H atoms were refined anisotropically, and the H atom positions were given geometrically. To rationalize some disordered F and C atoms on the hfac− co-ligand, commands of ISOR, SIMU, and DELU were used.

4. Conclusions

In this contribution, three novel biradical Ln-based complexes have been successfully prepared by utilizing the 5-(1-pyrazolyl) phenyl modified nitronyl nitroxide biradical NITPhPzbis. Complexes 1–3 feature a four-spin binuclear structure in which the NITPhPzbis serves as a bridging and chelating ligand. Magnetic studies show that complex 3 exhibits obvious slow magnetic relaxation behavior. The nitronyl nitroxide radical-Ln complex has long been an attractive strategy for constructing molecular nanomagnets. But research on nitronyl nitroxide biradical-Ln chemistry is still limited. This work discloses that nitronyl nitroxide biradical is effective building block for constructing Ln-based complexes. In the follow-up work, we will try to develop novel molecular magnetic materials presenting intriguing topologies and magnetic properties by changing the functional group in biradical and/or introducing 3d spin.

Supplementary Materials

The following are available online at https://0-www-mdpi-com.brum.beds.ac.uk/2312-7481/6/4/48/s1, Tables S1 and S2: Selected bond lengths [Å], bond angles [°] and SHAPE analyses for LnIII ions in complexes 1–3; Scheme S1: Synthesis of NITPhPzbis ligand; Figure S1: PXRD patterns for 1–3 at room temperature; Figure S2: IR spectra for 1–3; Figures S3 and S4: Binuclear structure of 2–3 and coordination polyhedra of LnIII in 2–3; Figures S5 and S6: Crystal packing diagram of 2–3; Figures S7 and S8: M vs. H plots for 2–3 at 2 K; Figure S9: Temperature dependencies of χ’ and χ” for 2 in zero dc field; Figure S10: Temperature dependency of χ’ for 3 in zero dc field; Figure S11: Frequency dependencies of χ’ and χ” for 3 in the dc fields of 200–4900 Oe. Crystallographic data for 1–3 (CIF); CCDC 2027496-2027498 include the complementary crystallographic data and relevant data can be obtained by www.ccdc.cam.ac.uk/data_request/cif.

Author Contributions

L.L. and L.X. designed the study. L.X. performed the experiments and wrote the paper. L.X., J.H., X.H. and L.L. performed the magnetic data analysis and revised the paper. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the National Natural Science Foundation of China (Nos. 21773122 and 21471083).

Acknowledgments

L.C. Li thanks the National Natural Science Foundation of China.

Conflicts of Interest

There are no conflicts to declare.

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Magnetochemistry 06 00048 sch001 550
Scheme 1. NITPhPzbis ligand.
Scheme 1. NITPhPzbis ligand.
Magnetochemistry 06 00048 sch001
Magnetochemistry 06 00048 g001 550
Figure 1. (a) The binuclear structure of 1(color code: violet-Gd, gray-C, red-O, blue-N, H and F atoms are omitted; There is weak hydrogen bond interaction between the pyrazolyl-N (N6 ) and the coordinated water molecule in which the distance of O17water(H-donor)⋅⋅⋅N6pyrazol(H-acceptor) is 2811 Å and the angle of O17water-H⋅⋅⋅N6pyrazol is 148.91°.). (b) Coordination polyhedra of Gd1 and Gd2 in 1.
Figure 1. (a) The binuclear structure of 1(color code: violet-Gd, gray-C, red-O, blue-N, H and F atoms are omitted; There is weak hydrogen bond interaction between the pyrazolyl-N (N6 ) and the coordinated water molecule in which the distance of O17water(H-donor)⋅⋅⋅N6pyrazol(H-acceptor) is 2811 Å and the angle of O17water-H⋅⋅⋅N6pyrazol is 148.91°.). (b) Coordination polyhedra of Gd1 and Gd2 in 1.
Magnetochemistry 06 00048 g001
Magnetochemistry 06 00048 g002 550
Figure 2. Crystal packing diagram of 1.
Figure 2. Crystal packing diagram of 1.
Magnetochemistry 06 00048 g002
Magnetochemistry 06 00048 g003 550
Figure 3. χMT vs. T curve for 1; Inset: M vs. H plot for 1 at 2 K (red-line and blue-line: best fitted curves by PHI).
Figure 3. χMT vs. T curve for 1; Inset: M vs. H plot for 1 at 2 K (red-line and blue-line: best fitted curves by PHI).
Magnetochemistry 06 00048 g003
Magnetochemistry 06 00048 g004 550
Figure 4. χMT vs. T curves for compounds 2 and 3.
Figure 4. χMT vs. T curves for compounds 2 and 3.
Magnetochemistry 06 00048 g004
Magnetochemistry 06 00048 sch002 550
Scheme 2. Scheme 2. Magnetic communications in complex 1.
Scheme 2. Scheme 2. Magnetic communications in complex 1.
Magnetochemistry 06 00048 sch002
Magnetochemistry 06 00048 sch003 550
Scheme 3. Spin polarization mechanism for the magnetic coupling mediated by m-phenylene ring between two mono-radicals.
Scheme 3. Spin polarization mechanism for the magnetic coupling mediated by m-phenylene ring between two mono-radicals.
Magnetochemistry 06 00048 sch003
Magnetochemistry 06 00048 g005 550
Figure 5. (a) Temperature-dependent χ” signals for 3 at zero dc field. (b) The ln(χ”/χ’) vs. 1/T graph for 3 (solid lines: fitting results).
Figure 5. (a) Temperature-dependent χ” signals for 3 at zero dc field. (b) The ln(χ”/χ’) vs. 1/T graph for 3 (solid lines: fitting results).
Magnetochemistry 06 00048 g005
Magnetochemistry 06 00048 g006 550
Figure 6. Magellan predicted magnetic anisotropy axes (green-rods) on DyIII centers in complex 3.
Figure 6. Magellan predicted magnetic anisotropy axes (green-rods) on DyIII centers in complex 3.
Magnetochemistry 06 00048 g006
Table
Table 1. Crystallographic data and structure refinement parameters for 1–3.
Table 1. Crystallographic data and structure refinement parameters for 1–3.
Complex1 Gd2 Tb3 Dy
FormulaC53H38F36Gd2N6O17C53H38F36Tb2N6O17C53H38F36Dy2N6O17
M, g·mol−12029.392032.732039.89
T/K113(2)113(2)113(2)
Crystal systemtriclinictriclinictriclinic
Space groupPīPīPī
a/Å11.976(2)11.997(2)11.997(2)
b/Å13.060(3)13.050(3)13.009(3)
c/Å26.438(5)26.470(5)26.471(5)
α/deg78.39(3)78.04(3)78.07(3)
β/deg77.93(3)77.70(3)77.76(3)
γ/deg64.89(3)64.80(3)64.83(3)
V/Å33632.1(16)3631.8(16)3622.2(16)
Z222
Dcalcd/g·cm–31.8561.8591.870
μ/mm−11.9692.0902.206
θ/deg1.588–25.0091.895–25.0091.588–25.009
F(000)197219761980
Reflns collected27,87130,36234,633
Unique reflns/Rint12,651/0.071712,514/0.051212,738/0.0711
GOF (F2)1.0781.0341.019
R1/wR2 (I > 2σ(I))0.0717/0.17820.0522/0.14160.0571/0.1538
R1/wR2 (all data)0.0921/0.22020.0632/0.15090.0737/0.1752
R1 = Σ(||Fo| − |Fc||)/Σ|Fo|, wR2 = [Σw(|Fo|2 − |Fc|2)2/Σw(|Fo|2)2]1/2.
Table
Table 2. The key bond lengths [Å] and bond angles [°] for 1–3.
Table 2. The key bond lengths [Å] and bond angles [°] for 1–3.
Complex1 Gd2 Tb3 Dy
Ln–Orad2.383(8)
2.472(7)
2.454(7)		2.365(5)
2.466(4)
2.437(4)		2.352(6)
2.460(5)
2.429(5)
Ln–Ohfac
Ln–OH2O		2.343(9)–2.412(7)
2.378(7)		2.323(5)–2.399(5)
2.373(4)		2.306(6)–2.390(5)
2.364(5)
Orad–Ln–Orad82.0(3)82.34(16)82.0(2)
Orad–Ln–OH2O77.7(2)77.91(15)77.69(17)

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Xi, L.; Han, J.; Huang, X.; Li, L. Nitronyl Nitroxide Biradical-Based Binuclear Lanthanide Complexes: Structure and Magnetic Properties. Magnetochemistry 2020, 6, 48. https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry6040048

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Xi L, Han J, Huang X, Li L. Nitronyl Nitroxide Biradical-Based Binuclear Lanthanide Complexes: Structure and Magnetic Properties. Magnetochemistry. 2020; 6(4):48. https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry6040048

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Xi, Lu, Jing Han, Xiaohui Huang, and Licun Li. 2020. "Nitronyl Nitroxide Biradical-Based Binuclear Lanthanide Complexes: Structure and Magnetic Properties" Magnetochemistry 6, no. 4: 48. https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry6040048

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