Magnetic Dynamics of a Neodymium(III) Single-Ion Magnet - Inorganic

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Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX

Magnetic Dynamics of a Neodymium(III) Single-Ion Magnet Yan-Cong Chen,* Xin-Shuo Huang, Jun-Liang Liu, and Ming-Liang Tong* Key Lab of Bioinorganic and Synthetic Chemistry of Ministry of Education, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, P. R. China

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S Supporting Information *

ABSTRACT: Slow relaxation of magnetization is observed in a neodymium(III) single-ion magnet based on phosphine oxide, which successfully extends our pentagonal bipyramidal family to light lanthanides. Comprehensive magnetic characterizations reveal that the magnetic dynamics follow the power law that corresponds to a Raman process, despite an energy splitting of 207 cm−1 evidenced by the ab initio calculation. Compared with a similar complex, the magnetic dynamics and magneto-structural correlations are clarified, providing deeper insight into the pursuit of promising light lanthanide single-molecule magnets.

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INTRODUCTION Single-molecule magnets (SMMs) are bistable systems in which the magnetic moment can be trapped in either one of the magnetic states.1 As one of the most characteristic properties of SMMs, slow relaxation of magnetization makes them possible to play a promising role in high-density information storage. On the other hand, quantum tunneling of magnetization (QTM) opens up the possibility for quantum processing and spintronics.2−6 From the discovery of {Mn12} until now, a lot of SMMs with a large energy barrier and high blocking temperature are reported.7−12 The recent progress in SMMs is focused on lanthanide ions,13 especially the heavy lanthanides such as Tb(III),14−17 Dy(III),11,12,18−25 Ho(III),26−28 and Er(III).29−32 Thanks to the large spin−orbit interaction and crystal field splitting, huge energy barriers are possible in lanthanide SMMs, such as 1025 K for [Dy(bbpen)Br],23 1815 K for [Dy(OtBu)2(py)5]+,25 and 1837 K for [Dy(Cpttt)2]+.11,12 This cannot be achieved by the ongoing understanding of the magneto-structural correlations, which have been guiding researchers to design, synthesize, and optimize these SMMs based on the crystal field theory.33 In addition, the QTM that is usually fast can be effectively suppressed by magnetic interactions8,9 and/or symmetry designs,34 so that the relaxation time and magnetic blocking temperature can be greatly boosted. On the contrary, the development of light lanthanide SMMs falls far behind, with only numbered cases based on Ce(III) and Nd(III)35−40 that can exhibit slow relaxation of magnetization. In the majority of these complexes, the QTM is usually too fast at a zero field, so the slow relaxation of magnetization can only be observed in the presence of a dc field, which highly limits their possibility as competing candidates compared with the heavy lanthanide SMMs. In addition, although some complexes process relatively large energy barriers (as evidenced by the ab initio calculation), their magnetic © XXXX American Chemical Society

relaxation does not go through the thermally activated Orbach process, but through a direct/Raman process instead.39 Therefore, it is still a question how to understand and tailor the magnetic dynamics of light lanthanide SMMs. On the basis of our successful SMM family incorporating phosphine oxides, here we report the synthesis, structure, and magnetic properties of a neodymium(III) single-ion magnet (SIM), namely, [Nd(CyPh2PO)2(H2O)5]I3·2(CyPh2PO)· 3EtOH (1, CyPh2PO = cyclohexyl(diphenyl)phosphine oxide). Combined with the ab initio calculation, it is evidenced that the compressed pseudo-D5h coordination environment of Nd(III) in 1 results in a quite large energy splitting exceeding 200 cm−1 between the ground state and the first excited state. However, the magnetic dynamics for 1 deviates much from the Arrhenius law, but instead follows the power law that corresponds to a Raman mechanism. Therefore, we also reinvestigate a similar complex, the first reported zero-field NdSIM based on phosphonic diamide,40 and compare their magneto-structural correlations and magnetic dynamics.

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EXPERIMENTAL SECTION

Materials. All reagents were commercially available and used as received without further purification unless otherwise noted. Hydrated NdI3 stock solution was obtained from mixing hydrated NdCl3 and NaI (1:3.1) in EtOH and removing the deposited NaCl by filtration. Synthesis. [Nd(CyPh2PO)2(H2O)5]I3·2(CyPh2PO)·3EtOH (1) was synthesized by mixing hydrate NdI3 (0.4 mmol) and CyPh2PO (0.8 mmol) in a H2O/EtOH (1:19, 4 mL) mixed solution, followed by slow evaporation in ambient conditions to almost dryness and then recrystallize in EtOH. Colorless crystals suitable for X-ray analysis and other characterizations were collected via filtration, washed with cold EtOH, and dried in air (yield ca. 40%). Analysis (calculated, Received: July 13, 2018

A

DOI: 10.1021/acs.inorgchem.8b01957 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry experimental) for C78H112P4I3NdO12: C (49.55, 49.85) and H (5.97, 5.77). IR (cm−1): 3166br, 2923s, 2851m, 1438m, 1138s, 1117s, 1073s, 1045w, 1026w, 998m, 919m, 888w, 824w, 763w, 723s, 697s, 688s, 593m, 557s, 530s, 507m. Characterization. The elemental analyses were performed with an Elementar Vario-EL CHN elemental analyzer. The IR spectra were recorded using a PerkinElmer Frontier FT-IR spectrometer. The powder XRD patterns were recorded on a Bruker D8 X-ray diffractometer (CuKα). Single-crystal diffraction data were recorded at 120(2) K on a Bruker D8 QUEST diffractometer with MoKα radiation, and solved using direct methods and refined using the SHELXTL program (Table S1).41 The disordered solvent molecules in the voids could not be solved from the crystal structure, and they were determined via elemental analysis. The magnetic measurements were performed on the polycrystalline samples using a Quantum Design MPMS XL-7 SQUID and a MPMS3 SQUID-VSM magnetometer. Diamagnetic correction was performed based on Pascal’s coefficients. Computational Details. All multiconfigurational ab initio calculations were carried out with OpenMOLCAS42 and are of the CASSCF/RASSI type. The Cholesky decomposition threshold was set to 1 × 10−8 to save disk space. An entire molecule and its second coordination sphere (same as Figure 1) are included, and the

Nd(III) ions are located in a compressed pentagonal bipyramidal coordination environment, with the axial Nd− O(PR3) bond lengths of 2.279 Å and the average equatorial Ho−O(H2) bond length of 2.437 Å (Table 1). Continuous Table 1. Selected Bond Lengths and Bond Angles for 1a bond length (Å) Nd−O1 Nd−O1A Nd−O1W Nd−O2W Nd−O2WA Nd−O3W Nd−O3WA a

bond angle (deg)

2.279(6) 2.279(6) 2.411(7) 2.452(7) 2.452(7) 2.436(6) 2.436(6)

O1−Nd−O1A O1W−Nd−O2W O2W−Nd−O3W O3W−Nd−O3WA O3WA−Nd−O2WA O2WA−Nd−O1W

177.3(3) 71.06(16) 72.6(2) 72.8(3) 72.6(2) 71.06(16)

Symmetry code (A): 1 − x, y, 0.5 − z.

Shape Measures (CShM) calculation47 reveals that complex 1 only deviates from ideal D5h by a little value of 0.159 (Table 2), which is the most regular pentagonal bipyramidal Nd(III) complex to the best of our knowledge. Table 2. Continuous Shape Measures Calculations for 1a PBPY-7 (D5h)

COC-7 (C3v)

CTPR-7 (C2v)

JPBPY-7 (D5h)

0.159

7.627

5.712

2.658

a

PBPY-7 = pentagonal bipyramid; COC-7 = capped octahedron; CTPR-7 = capped trigonal prism; JPBPY-7 = Johnson pentagonal bipyramid J13. The others with CShM values > 10 are omitted.

The second coordination sphere of 1 is formed by fivepointed-star-like hydrogen bonds between the coordinated water molecules and the free ligands/anions, which further stabilize the pseudo-D5h local symmetry of Nd(III). In the crystal structure, complex 1 is packed in an orthorhombic C2221 space group with intermolecular π−π stacking between the ligands, and the nearest Nd···Nd distance is 14.09 Å (Figure S1). The ab initio calculations based on the crystal structure of 1 show that the main anisotropy axis of the ground Kramers doublet lies around 2.9° from the pseudo-D5h axis, as expected for such compressed coordination environment accommodating the Nd(III) ion (yellow arrow in Figure 1). Magnetic Properties. Direct-current (dc) magnetic susceptibilities were measured on polycrystalline samples of 1 under 0.1 T, showing steady decrease from 1.52 cm3 K mol−1 at room temperature to 1.15 cm3 K mol−1 at 2 K (Figure 2). These values are slightly lower than that of a free Nd(III) ion (4I9/2, 1.64 cm3 K mol−1) mainly because of the significant crystal field splitting under an anisotropic coordination environment. At low temperature, the magnetization approaches a saturation of ∼1.5 Nβ, with overlapping M vs H/ T curves (inset of Figure 2), indicating large anisotropy and far-separated energy levels for Nd(III). To probe the magnetic dynamics of 1, alternating-current (ac) magnetic susceptibilities were measured in a zero dc field (Figure 3) and in an optimized 0.2 T dc field (Figure 4), both of which show typical patterns for lanthanide SIMs. From the temperature-dependent out-of-phase susceptibilities (χM′′), the peaks for 1488 Hz are located at 7.5 K in a zero dc field, and 8.5 K in a 0.2 T dc field, respectively. When the temperature decreases, the peaks of the frequency-dependent χM′′ move to lower frequencies as ∼30 Hz in a zero dc field, while those in a 0.2 T dc field move to as low as ∼0.1 Hz at 2 K. Such behavior

Figure 1. Coordination environment of Nd(III) in 1. The yellow arrow represents the orientation of the main magnetic axis of the ground Kramers doublet obtained from the ab initio calculation. The free CyPh2PO ligands are simplified, and the H atoms are omitted in the figure for clarity. Color codes: Nd, cyan; P, purple; I, brown; O, red; C, gray; H, light gray. coordinates of atoms are extracted from the experimentally determined crystal structure without further optimization. Two ANO-RCC basis set approximations have been employed:43−45 a larger one for the following discussion uses a triple-ζ basis with polarization functions (VTZP) for Nd(III), while a smaller one uses a double-ζ basis with polarization functions (VDZP) for comparison and verifies each other. Active space of the CASSCF method included three electrons in seven 4f orbitals of Nd(III). All 35 quartets were optimized in state-averaged calculations and then mixed by spin−orbit coupling using RASSI approach to obtain the g-tensors, energies, main magnetic axis as well as the magnetizations.46

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RESULTS AND DISCUSSION Crystal Structure. Complex 1 is synthesized from NdI3 and CyPh2PO in a H2O/EtOH mixed solution in ambient condition (see the Experimental Section for details). Similar to its Ho(III) derivative,28 the molecular structure consists of a [Nd(CyPh2PO)2(H2O)5]3+ core surrounded by two CyPh2PO ligands, three I− ions, and lattice solvents (Figure 1). The B

DOI: 10.1021/acs.inorgchem.8b01957 Inorg. Chem. XXXX, XXX, XXX−XXX

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Figure 2. Temperature dependence of the molar magnetic susceptibility χMT products for 1 under a 0.1 T dc field. The solid line corresponds to the ab initio calculations (scaled down by 0.957). Inset: magnetization (M) versus H/T for 1.

Figure 4. Temperature dependence (a) and frequency dependence (b) of the in-phase χM′T product and out-of-phase χM′′ for 1 in a 0.2 T dc field with an AC frequency of 0.1−1488 Hz (logarithm interval).

magnetic dynamics, the temperature dependency of τ is plotted in Figure 5. In a zero dc field, τ rises slowly with the decrease

Figure 3. Temperature dependence (a) and frequency dependence (b) of the in-phase χM′T product and out-of-phase χM′′ for 1 in a zero dc field with an AC frequency of 1−1488 Hz (logarithm interval).

Figure 5. Temperature dependence of the relaxation time τ in a zero dc field (blue) and 0.2 T dc field (red) for 1. The solid lines are the best fit to the respective relaxation equation.

is indicative of a faster relaxation process and/or QTM a zero field, which is common in lanthanide SIMs. These processes can be suppressed by applying an external dc field and/or diluting the molecule into a diamagnetic matrix, and then a longer relaxation time can be obtained. Here, such behavior is clearly evidenced by the frequency-dependent ac susceptibilities in various dc fields (Figure S4), where the peak at high frequencies is suppressed by an external dc field, and the slow relaxation process gradually emerges at low frequencies. The relaxation times (τ) for 1 are obtained by fitting the ac magnetic susceptibilities based on the generalized Debye law (Figures S5 and S6). In a zero dc field, the distribution of τ is moderate (α = 0.13−0.29), but in a 0.2 T dc field, the distribution is narrower (α = 0.02−0.13). To determine the

of T, and generally tends to become temperature-independent below ∼3 K due to QTM and finally reads 5.0(3) ms at 2 K. In a 0.2 T dc field, τ keeps rising and goes to as long as 1.46(7) s at 2 K. Fitting these data with common Arrhenius law does not generate satisfactory results; instead, the fittings are fairly well by using the combination of a Raman term and a QTM term, namely, τ−1 = CTn + τQTM−1, yielding n = 5.12(6) and τQTM = 5.1(2) ms in a zero dc field (blue line in Figure 5). Moreover, the magnetic dynamic in a 0.2 T dc field shows almost perfect linear dependency in a log−log scale, which can be fitted by solely one Raman term with n = 6.54(12) (red line in Figure C

DOI: 10.1021/acs.inorgchem.8b01957 Inorg. Chem. XXXX, XXX, XXX−XXX

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strategy, a perfect D5h coordination environment shall eliminate the QTM from the crystal field aspect, and indeed the main anisotropy axis for 1 lies very close to the pseudo-D5h rotational axis by only 2.9° (Figure 1). Therefore, with 1, we successfully extend our Ln(R3PO)5(H2O)5 family to the light lanthanides, where the strongly electronegative phosphine oxide dominates the axial anisotropy, while the transverse anisotropy is minimized with the pseudo five-fold symmetry of the equatorial water molecules. The five lowest Kramers doublets that split from the 4I9/2 ground term of Nd(III) span across a large energy range of 362 cm−1 (Table 2). The first excited Kramers doublet is located at 207 cm−1 above the ground Kramers doublet and shows significantly larger transverse anisotropy (gx = 0.5319 and gy = 0.6672). A parallel calculation is also performed using a smaller basis set, and the results are consistent and prove the convergence and robustness of the methodology (Tables S2 and S3). However, fitting the experimental temperature dependence of the relaxation time according to the Arrhenius law only gives a tiny apparent Uapp = ∼ 30 cm−1, which is almost an order of magnitude smaller than the calculated energy barrier. Such large disagreement rules out the possibility that 1 relaxes through the common Orbach process. Instead, judging from the linear τ−T dependency in a log−log scale, the relaxation dynamics must be dominated by another process that obeys the power law, such as the Raman process. Further Discussion. At this point, it is somewhat surprising that 1 seems to exhibit much different magnetic dynamics than the first zero-field Nd-SIM, (2),40 which is reported to possess Ueff = 24.69 K in a zero dc field and Ueff = 39.21 K in a 0.2 T dc field. These values are also far lower than their calculated energy barrier of 302 K, and it could hardly be explained by QTM, which should be effectively suppressed by an external dc field. Comparing 1 with 2, we find that, although their ligands are chemically different (phosphine oxide vs phosphonic diamide), the core structure is generally quite similar as a compressed pentagonal bipyramidal [Nd(R3PO)2(H2O)]3+ motif. The CShM value for 2 is 0.286 regarding a perfect D5h symmetry, which is similar to but larger than that of 1 due to the slightly distorted coordination geometry. Although the crystal fields can be impacted by the distribution of the effective charges of the coordinated oxygen atoms, ab initio calculation for 2 also suggests comparative g-tensors of gx = 0.02, gy = 0.02, and gz = 6.30), which are also only a little different from those of 1. So, it becomes an issue of magnetostructural correlations that lies in the way of understanding and developing these Nd-SIMs. To clarify such confusion, we managed to prepare complex 2 according to the literature and reanalyzed the magnetic dynamics (Figures S7−S9). Here we focus on the ac susceptibilities in a 0.2 T dc field, because, in a zero field, there are both QTM and TA-QTM as reported, which results in multiple peaks and makes it difficult and tricky to identify the relaxation dynamics. After a careful evaluation, it is clear that the relaxation time for 2 also follows the power law (Figure 7), and the best fit with only one Raman process yields a similar n = 6.29(5) as that of 1. Therefore, the magnetic dynamics for 1 and 2 are in fact consistent and shall verify each other, while the tiny difference may originate from the structure, size, and rigidity of the ligands, which alters the lattice vibrations that play an important role in the spin− phonon coupling.

5). These values agree well with those of our previously reported hexagonal bipyramidal Ce(III) and Nd(III) SIMs,39 which exhibit Raman relaxation with n = 6.9 and 6.4, respectively. It should be noted that the common n = 7 or 9 are based on a series of hypothesis such as the Debye model with the long wavelength approximations for the lattice phonons. However, the exact n value for the Raman process depends on the structure of magnetic states and phonon spectrum, which is much more complicated and varies with magnetic field.48 Since the relaxation times for 1 at low temperature are quite long, especially in the presence of a dc field, butterfly-shaped magnetic hysteresis loops can be observed at 2 K (Figure 6).

Figure 6. Normalized magnetic hysteresis loops for 1 at a field sweep rate of 0.02 T/s at the indicated temperatures.

The loops are basically closed near zero field, but show a narrow, but reproducible, opening between 0 and 0.5 T. Such a pattern is consistent with the result of ac magnetism, where the relaxation time at a zero field is much faster than that in a 0.2 T dc field. A larger opening of the magnetic hysteresis loops can be expected in lower temperature, as the relaxation time in a 0.2 T dc field is still highly temperature-dependent down to 2 K (Figure 5). Ab Initio Calculation. For the deeper understanding of the magneto-structural correlations in such a system, quantum chemistry calculations were performed at the CASSCF level based on the crystal structure for 1 (see the Experimental Section for details). The 4I9/2 ground term of Nd(III) in 1 splits into five Kramers doublets with significant anisotropy (Table 3). The calculated g-tensors of the ground doublet are highly axial, as evidenced by a prominent gz = 6.2876 along with much smaller gx = 0.0109 and gy = 0.0172. Such large axial anisotropy with small transverse terms is the key to the SMM properties for 1 even in a zero field, because the QTM between ground states can be reduced. As predicted by the symmetry Table 3. Ab Initio Calculated g-Tensors and Energies of the Lowest Five Kramers Doublets for 1 KD

gx

gy

gz

E/cm−1

1 2 3 4 5

0.0109 0.5319 3.5146 0.1786 0.6705

0.0172 0.6672 2.9659 1.1805 0.823

6.2876 6.0065 0.4407 3.0281 4.9465

0 207 267 289 362 D

DOI: 10.1021/acs.inorgchem.8b01957 Inorg. Chem. XXXX, XXX, XXX−XXX

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via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (Y.-C.C.). *E-mail: [email protected] (M.-L.T.). ORCID

Yan-Cong Chen: 0000-0001-5047-3445 Jun-Liang Liu: 0000-0002-5811-6300 Ming-Liang Tong: 0000-0003-4725-0798 Figure 7. Temperature dependence of the relaxation time τ in a 0.2 T dc field (red) for 2. The solid lines are the best fit to the Raman relaxation equation.

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the National Key Research and Development Program of China (2018YFA0306001), the NSFC (Grant nos. 21620102002 and 21701198), China Postdoctoral Science Foundation (National Postdoctoral Program for Innovative Talents, Grant BX201700295 and 2017M620396), and Pearl River S&T Nova Program of Guangzhou (201806010192).

Indeed, in a system with multiple relaxation pathways, the total relaxation rate is obtained by the sum of all possible processes, namely, τ−1 = τOrbach−1 + τRaman−1 + τDirect−1 + τQTM−1 + ···. As a result, the faster a process is, the stronger it dominates the relaxation dynamics. It should be noted that the presence of larger gx and gy also represents stronger mixing of different states, no matter if they are ground states or excited states. Such mixing not only facilitates the QTM but also speeds up the other relaxation processes. If a system can go through several relaxation pathways whose relaxation rates differ by several orders of magnitude, only the fastest process can be observed.

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(1) Gatteschi, D.; Sessoli, R.; Villain, J. Molecular nanomagnets; Oxford University Press: Oxford, U.K., 2006. (2) Leuenberger, M. N.; Loss, D. Quantum computing in molecular magnets. Nature 2001, 410, 789−793. (3) Bogani, L.; Wernsdorfer, W. Molecular spintronics using singlemolecule magnets. Nat. Mater. 2008, 7, 179−186. (4) Mannini, M.; Pineider, F.; Sainctavit, P.; Danieli, C.; Otero, E.; Sciancalepore, C.; Talarico, A. M.; Arrio, M.-A.; Cornia, A.; Gatteschi, D.; Sessoli, R. Magnetic memory of a single-molecule quantum magnet wired to a gold surface. Nat. Mater. 2009, 8, 194−197. (5) Thiele, S.; Balestro, F.; Ballou, R.; Klyatskaya, S.; Ruben, M.; Wernsdorfer, W. Electrically driven nuclear spin resonance in singlemolecule magnets. Science 2014, 344, 1135−1138. (6) Shiddiq, M.; Komijani, D.; Duan, Y.; Gaita-Ariño, A.; Coronado, E.; Hill, S. Enhancing coherence in molecular spin qubits via atomic clock transitions. Nature 2016, 531, 348−351. (7) Sessoli, R.; Gatteschi, D.; Caneschi, A.; Novak, M. A. Magnetic bistability in a metal-ion cluster. Nature 1993, 365, 141−143. (8) Rinehart, J. D.; Fang, M.; Evans, W. J.; Long, J. R. Strong exchange and magnetic blocking in N23−-radical-bridged lanthanide complexes. Nat. Chem. 2011, 3, 538−542. (9) Rinehart, J. D.; Fang, M.; Evans, W. J.; Long, J. R. A N23− Radical-Bridged Terbium Complex Exhibiting Magnetic Hysteresis at 14 K. J. Am. Chem. Soc. 2011, 133, 14236−14239. (10) Zadrozny, J. M.; Xiao, D. J.; Atanasov, M.; Long, G. J.; Grandjean, F.; Neese, F.; Long, J. R. Magnetic blocking in a linear iron(I) complex. Nat. Chem. 2013, 5, 577−581. (11) Guo, F.-S; Day, B. M.; Chen, Y.-C.; Tong, M.-L.; Mansikkamaki, A.; Layfield, R. A. A Dysprosium Metallocene Single-Molecule Magnet Functioning at the Axial Limit. Angew. Chem., Int. Ed. 2017, 56, 11445−11449. (12) Goodwin, C. A. P.; Ortu, F.; Reta, D.; Chilton, N. F.; Mills, D. P. Molecular magnetic hysteresis at 60 K in dysprosocenium. Nature 2017, 548, 439−442. (13) Woodruff, D. N.; Winpenny, R. E. P.; Layfield, R. A. Lanthanide Single-Molecule Magnets. Chem. Rev. 2013, 113, 5110− 5148.

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CONCLUSION In conclusion, we investigated the magnetic dynamics of a pentagonal bipyramidal neodymium(III) SIM based on phosphine oxide, which exhibits slow relaxation of magnetization both at a zero dc field and in an optimized 0.2 T dc field. However, the relaxation dynamics follows the power law corresponding to the Raman process. Through the ab initio calculation and the comparison with a similar complex, the magneto-structural correlations as well as the impact on relaxation pathways are discussed, and we emphasize the importance of the careful determination of relaxation process in the evaluation. Finally, we also expected that the further investigation of light lanthanide SMMs should pay more attention to the origin of the Raman process, especially from the aspect of lattice vibration. Once we manage to slow it down, the magnetic relaxation times for light lanthanide SMMs may be largely increased, and their awkward role as short slabs in molecular magnets will become history.

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REFERENCES

ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.8b01957. Crystallographic table and packing structure, powder Xray diffraction patterns, additional figures of magnetic characterizations, details of ab initio calculations (PDF) Accession Codes

CCDC 1843383 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge E

DOI: 10.1021/acs.inorgchem.8b01957 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

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DOI: 10.1021/acs.inorgchem.8b01957 Inorg. Chem. XXXX, XXX, XXX−XXX