Chiral Erbium(III) Complexes: Single-Molecule Magnet Behavior

7 days ago - Thus, the nuclearity could be controlled by the reaction temperature. Their chirality was studied with circular dichroism (CD) spectra...
1 downloads 0 Views 4MB Size
Download PDF
Article Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX

pubs.acs.org/IC

Chiral Erbium(III) Complexes: Single-Molecule Magnet Behavior, Chirality, and Nuclearity Control Min Feng,*,† Bang-Heng Lyu,† Ming-Hui Wang,† Wei-Wei Wu,† Yan-Cong Chen,† Guo-Zhang Huang,† Wei-Quan Lin,‡ Si-Guo Wu,† Jun-Liang Liu,† and Ming-Liang Tong*,† †

Downloaded via UNIV AUTONOMA DE COAHUILA on August 8, 2019 at 03:21:56 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

Key Laboratory of Bioinorganic and Synthetic Chemistry of the Ministry of Education, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, P. R. China ‡ School of Chemistry and Chemical Engineering, Guangzhou University, Guangzhou 510006, P. R. China S Supporting Information *

ABSTRACT: The reactions of chiral ligand (R)/(S)-1,1′-binaphthyl2,2′-diyl phosphate (R-HL/S-HL) and ErCl3·6H2O afford two pairs of diand tetranuclear enantiomers [Er2(R/S-L)4(EtOH)6]Cl2·6.5EtOH (R-1, S-1) and [Er4(PO4)(R/S-L)8(EtOH)3(H2O)]2Cl(OH)·15EtOH·11H2O (R-2, S-2). The nuclearity of these complexes is controllable and depends on the reaction temperature with a template effect. Their chirality was evidenced by circular dichroism (CD) spectra. R-1 exhibits two magnetic relaxation pathways under a zero field, with an apparent barrier of 40 K. Ab initio calculations revealed a ferromagnetic dipolar interaction between these two Er(III) ions, the equatorial nature of the ligand field, and the probable origin of the two relaxations.

■

INTRODUCTION Single-molecule magnets (SMMs) exhibit magnetic bistability, which are valued for the applications in high-density data storage, quantum computation, and molecular spintronics.1−5 Recently, a record blocking temperature of 80 K was reported for a Dy metallocene SMM, opening the access for the practical applications above liquid nitrogen temperatures.6−9 Indeed, lanthanide ions are, so far, the best spin source for the construction of high-performance SMMs, owning to their large magnetic moments and high anisotropy. Er(III) is also highly anisotropic and possesses large magnetic moments as Dy(III). In fact, the anisotropy of Er(III) and Dy(III) is different, which is prolate and oblate, respectively. As a result, they require different ligand field to maximize their magnetic anisotropy. Unlike oblate Dy(III) ion, the ideal coordination environment for prolate Er(III) ion to possess high anisotropy is equatorial coordination (Figure 1a).10,11 For example, to minimize the axial ligand field effect, some Er-SMMs are without axial ligands.12−14 Some Er-SMMs contain an eight-member ring, COT (cyclooctatetraene dianion) as the sandwiched ligand, taking the advantage of its big size to achieve larger zenith angle and thus the equatorial ligand field,15−20 with the energy barrier up to 300 cm−119 and blocking temperature up to 10 K.16 Given above, Er(III) is also suitable to form promising SMMs. However, the reported Er-SMMs are much less than Dy-SMMs, thus they are worth exploring. Apart from the research of different metal-based SMMs, multifunctional molecular magnet is another developing © XXXX American Chemical Society

Figure 1. (a) Two kinds of coordination environments for Ln(III): equatorial coordination (yellow) with large zenith angle θ for prolate Ln(III) ions, and axial coordination (red) with small θ for oblate Ln(III) ions. The black arrow represents the main magnetic axis. (b) Enantiomeric ligands R-HL and S-HL.

branch in this field. These multifunctional molecular magnets are usually formed by combining the metal ions with SMM properties and functional organic moieties as ligands. SMMs with chirality might possess additional properties such as magnetochiral dichroism,21 second harmonic generation,22 and ferroelectricity.23 To construct chiral SMMs, the following types of ligands were reported: chiral {N2} bidentate ligands,24−32 chiral {O2} β-diketonate ligands,33 and helical ligands28,29,31,34 for single-ion magnets (SIMs)35 and chiral bridging ligands36−40 for polynuclear SMMs. Given above, we intend to design SMMs with a chiral ligand (R)/(S)-1,1′-binaphthyl-2,2′-diyl phosphate41,42 (R-L/S-L, Received: March 2, 2019

A

DOI: 10.1021/acs.inorgchem.9b00616 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

well as the magnetizations using the SINGLE_ANISO routine.59 Dipolar magnetic interactions are included within POLY_ANISO program.60−62 Synthesis. [Er2(R-L)4(EtOH)6]Cl2·6.5EtOH (R-1). To the mixture of ErCl3··6H2O (38 mg, 0.1 mmol) and R-HL (70 mg, 0.2 mmol), 8 mL of ethanol was added without agitation. Pale-pink plate like crystals were obtained after 2 days and were washed with ethanol (yield 56%). Elemental analysis was performed on a freshly filtered crystalline sample which lost crystallinity quickly in air. The result of elemental analysis, calcd (%) for [Er 2 (R-L) 4 (EtOH) 6 ]Cl 2 ·8H 2 O (C92H100Cl2Er2O30P4): C 49.89, H 4.55. Found: C 49.67, H 4.72, indicates the lattice ethanol molecules are replaced by water molecules in air. TGA shows a weight loss of 18.98%, which agrees with the loss of eight water and six ethanol molecules (SI, Figure S8), confirming the composition and purity of the sample in air. IR (KBr, cm−1): 3340br, 3068m, 2974m, 1925w, 1830w, 1770w, 1622m, 1591m, 1508m, 1464m, 1431w, 1402w, 1365w, 1329m, 1238s, 1211s, 1111s, 1070s, 1043m, 991m, 966s, 947m, 872s, 818m, 750s, 719m, 696m, 658m, 633w, 590m, 567m, 538m, 484m, 465m, 442w, 415w. [Er2(S-L)4(EtOH)6]Cl2·6.5EtOH (S-1). S-1 was obtained as pale-pink plate like crystals by a method similar to that of R-1, except that S-HL was applied instead of R-HL. Yield: 60%. Elemental Analysis Calcd (%) for [Er2(S-L)4(EtOH)6]Cl2·8H2O (C92H100Cl2Er2O30P4): C 49.89, H 4.55. Found: C 49.94, H 4.65. IR (KBr, cm−1): 3332br, 3068m, 2974m, 1925w, 1832w, 1774w, 1620m, 1591m, 1508m, 1466m, 1433w, 1402w, 1369w, 1360w, 1329m, 1236s, 1209s, 1113s, 1070s, 1041m, 993m, 966s, 947m, 874s, 841w, 818m, 795w, 773w, 750s, 721m, 698m, 658m, 633w, 598m, 586m, 567m, 538m, 494m, 482m, 465m, 440w, 415w. [Er4(PO4)(R-L)8(EtOH)3(H2O)]2Cl(OH)·15EtOH·11H2O (R-2). The mixture of ErCl3·6H2O (38 mg, 0.1 mmol), R-HL (70 mg, 0.2 mmol), and 8 mL of ethanol was sealed in a Teflon-lined stainless container and kept at 100 °C for 48 h and then cooled to ambient temperature at a rate of 3.5 °C/h to form pale-pink prismatic crystals which were washed with ethanol (yield ca. 65%). Elemental Analysis Calcd: C, 52.14; H, 4.17. Found: C, 52.27; H, 4.23. IR (KBr, cm−1): 3621m, 3554m, 3311br, 3057m, 3010m, 2972m, 2926m, 2899m, 1913w, 1832w, 1767w, 1620m, 1591m, 1508m, 1466m, 1433w, 1402w, 1371w, 1360w, 1329m, 1257s, 1238s, 1209s, 1157m, 1113s, 1068s, 993m, 966s, 947m, 877m, 843w, 816m, 795w, 773w, 748m, 721m, 698m, 658m, 631w, 598m, 567m, 540m, 515w, 496m, 480m, 467m, 438w, 415w. [Er4(PO4)(S-L)8(EtOH)3(H2O)]2Cl(OH)·15EtOH·11H2O (S-2). S-2 was obtained as pale-pink prismatic crystals by a method similar to that of R-2, except that S-HL was applied instead of R-HL. Yield: 60%. Elemental Analysis Calcd: C, 52.14; H, 4.17. Found: C, 52.12; H, 4.13. IR (KBr, cm−1): 3620m, 3554m, 3300br, 3055m, 3012m, 2972m, 2933m, 2899m, 1911w, 1871w, 1830w, 1770w, 1620m, 1591m, 1508m, 1466m, 1433w, 1402w, 1369w, 1362w, 1329m, 1257s, 1238s, 1209s, 1157m, 1113s, 1068s, 993m, 966s, 947m, 877m, 843w, 816m, 795w, 773w, 748m, 721m, 698m, 658m, 631w, 598m, 567m, 540m, 515w, 496m, 480m, 467m, 438w, 415w.

Figure 1b). Two pairs of di- and tetranuclear enantiomers [Er 2 (R/S-L) 4 (EtOH) 6 ]Cl 2 ·6.5EtOH (R-1, S-1) and [Er 4 (PO 4 )(R/S-L) 8 (EtOH) 3 (H 2 O)] 2 Cl(OH)·15EtOH· 11H2O (R-2, S-2) were obtained at different temperature. The tetranuclear complexes R-2 and S-2 were formed with a PO4− template, which is probably degraded from the phosphate ligand at high temperature. Thus, the nuclearity could be controlled by the reaction temperature. Their chirality was studied with circular dichroism (CD) spectra.

■

EXPERIMENTAL SECTION

Materials and General Methods. The chiral ligands R-HL (98%) and S-HL (97%) were purchased from Macklin. All commercially available chemicals were used as received without further purification. The elemental analyses were performed with an Elementar Vario-EL CHN elemental analyzer. The IR spectra were recorded using a Bruker EQUINOX 55 FT-IR spectrometer. The CD spectra were recorded on a JASCO J1700 spectropolarimeter at room temperature, in the condition of: pitch 0.5 nm, DIT 1 s, bandwidth 8 nm, and speed 500 nm/min. Thermogravimetric analyses (TGA) were carried out on a NETZSCH TG209F1 thermogravimetric analyzer with freshly filtered crystalline samples. UV−vis-NIR absorptions were performed on a Shimadzu UV-3600Plus spectrometer. PXRD data were recorded on a Rigaku SmartLab X-ray diffractometer (Cu Kα) at room temperature, with the powder samples soaked with mother liquor. The magnetic measurements were performed using a Quantum Design MPMS XL-7 SQUID and an MPMS3 SQUID-VSM magnetometer. Polycrystalline samples were embedded in Vaseline to prevent torquing and soaked with mother liquor for the direct (dc) and alternating (ac) current susceptibility measurements, respectively. Diamagnetic correction was performed based on Pascal’s coefficients. X-ray Crystallography. Single-crystal diffraction data were recorded at 120 K on a Bruker D8 QUEST diffractometer with Mo Kα radiation for R-1. For S-1, R-2, and S-2, the data were recorded at 100 K on a Rigaku XtaLAB Synergy-DW diffractometer with Cu Kα radiation. The structures were solved by SHELXT methods with Olex2 program,43 and all non-hydrogen atoms were refined anisotropically by least-squares on F2 using the SHELXL.44−46 For R-2 and S-2, the contribution from the disordered solvent molecules in the voids was removed by SQUEEZE.47 For 2, the disordered solvent molecules were determined via elemental analysis and thermogravimetric analyses. Data has been deposited at the Cambridge Crystallographic Data Centre with the following CCDC numbers: 1900543, 1900544, 1900545, 1900546. The crystal data and structural refinement are listed in Supporting Information (SI, Table S1. Computational Details. The positions of hydrogen atoms are first optimized at DFT level using the pure GGA PBE exchange correlation functional,48,49 while those of the heavier atoms remain unchanged according to the crystal structure except that the Dy(III) are replaced by Y(III) to avoid convergence problems. Ahlrichs’ def2SVP basis sets are used in all DFT calculations. The core electrons of Y(III) are treated with an effective core potential (ECP).50,51 The DFT calculations were carried out using the Orca 4.0.1.2 code,52,53 and then all multiconfigurational ab initio calculations were carried out with OpenMOLCAS version 18.0954 and are of the CASSCF/ RASSI type. The Cholesky decomposition threshold was set to 1 × 10−8 to save disk space. An entire molecule is included, and the coordinates of atoms are extracted from the experimentally determined crystal structure. The neighboring lanthanide site is computationally replaced by the diamagnetic Lu(III). Three ANORCC basis set approximations have been employed: VTZP for Er(III) and Lu(III),55 VDZP for O and P,56 and VDZ for C and H.56,57 Active space of the CASSCF method included 11 electrons in seven 4f orbitals of Er(III). All 35 quartets were optimized in state-averaged calculations and then mixed by spin−orbit coupling using RASSI approach58 to obtain the g-tensors, energies, main magnetic axis as

■

RESULTS AND DISCUSSION Synthesis. The dinuclear complexes R-1 and S-1 were prepared by direct mixing of ErCl3·6H2O with the corresponding chiral ligand R-L/S-L in ethanol under ambient conditions, while the tetranuclear complexes R-2 and S-2 were isolated by solvothermal synthesis (Scheme 1). The PO43− anion in R-2 and S-2 is probably a decomposition product of the ligand under the solvothermal condition and acts as a template bridging ligand for the four Er(III) ions leading to the tetranuclear complexes. Crystal Structure. R-1/S-1 and R-2/S-2 are enantiomeric pairs, crystallize in orthorhombic P212121 and monoclinic P21 chiral space groups, respectively. The crystallinity of R-1 and S1 are poor when exposed in air due to the rapid desolvation and substitution of the lattice solvents, according to the B

DOI: 10.1021/acs.inorgchem.9b00616 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

three from ethanol molecules. SHAPE63 analyses reveal that the ligand arrangement leads to distorted capped trigonal prism (C2v) and capped octahedron (C3v) as coordination polyhedra for Er1 and Er2, respectively (Figure 3 and SI, Table

Scheme 1. Synthesis Routes for the Dinuclear and Tetranuclear Complexes R-1/S-1 and R-2/S-2

elemental and TG analysis (vide supra). Because R-1/S-1 and R-2/S-2 are enantiomeric, the structural description is performed only for R-1 and R-2. The asymmetric unit of dinuclear R-1 is composed of two Er(III) ions, four R-L ligands, six coordinating ethanol molecules, two chloride counterions, and six and a half ethanol molecules of crystallization (Figure 2). Two Er(III) ions are bridged via four μ−η1:η1 O−P−O moieties from four R-L ligands with an intramolecular Er1···Er2 distance of 4.5662(9) Å. The shortest intermolecular Er···Er distance was found to be 11.5487(16) Å. Two Er(III) ions are both seven-coordinated. Each of them is surrounded by seven O atoms, four from R-L ligands, and

Figure 3. (a) Coordination environment of R-1. (b) Coordination polyhedra in R-1, illustrating the distorted capped trigonal prismatic geometry for Er1 and capped octahedral geometry for Er2. Color code: Er, green; O, red; P, violet.

S2). The average angle of O atoms from the anionic chiral ligands and the metal centers, O1−Er1−O9, O5−Er1−O13, O2−Er2−O10, and O6−Er2−O14 is relatively large (124.6(2)°, Figure 3a and SI, Table S6). On the other side, the average angle of O atoms (O17−O22) from the neutral ethanol ligands and the metal centers is smaller (77.7(2)°, SI, Table S6). The average Er−O bond length is 2.287(6) Å, where the average bond length between Er and O atoms from the anionic R-L ligands (2.261(6) Å) is slightly shorter than the one from neutral ethanol ligands (2.321(7) Å) (SI, Table S5). Given the relatively large O−Er−O angles of the chiral ligands, these anionic ligands are located more equatorially than axially, which might lead to SMM behaviors for the prolate Er(III) ions (see more discussions in the ab initio calculations part). All the ligands maintain their R form as the starting free ligands. We found the crystal struct of the free ligand S-HL from CCDC (182411).64 Comparing the ligands before and after coordination in this dinuclear complex, the torsion angle and dihedral angles of two benzene or two naphthalene of the complex are slightly smaller (2−3°) than the free ligand (SI, Figure S7 and Table S10). To analyze the chirality, continuous chirality measures (CCM)65 were performed on the Er ions with their first (ErO7) and second (ErO7P4C3) coordination spheres. The resulting CCM values are close to zero (average 0.243, SI, Table S2) for the first coordination sphere, while the second coordination spheres give larger CCM values (average 1.03, SI, Table S2) because the second coordination spheres are closer to the chiral center of the binaphthyl groups. However, they are both much smaller than the chiral ligands RL− (average 6.29, SI, Table S4). These suggest the chirality is mainly located on the chiral ligands. In an asymmetric unit of R-2, two crystallographically independent tetranuclear [Er4(PO4)(R-L)8(EtOH)3(H2O)]+ cations (SI, Figure S4), one chloride, and one hydroxide counterion were found (Figure 4). In one tetranuclear cation,

Figure 2. Molecular structure of the dinuclear complex R-1. Ellipsoids are shown at the 30% probability. Hydrogen atoms, counterions, and crystallization molecules have been omitted for clarity. Color code: Er, green; O, red; P, violet; C, light yellow, light pink, light blue, and light green for different ligands; gray, ethanol. C

DOI: 10.1021/acs.inorgchem.9b00616 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

Figure 4. Molecular structure of the dinuclear complex R-2. Ellipsoids are shown at the 30% probability. Hydrogen atoms, counterions, and crystallization molecules have been omitted for clarity. Color code: Er, green; O, red; P, violet; C, light yellow for the four ligands on top, light blue for the four ligands at the bottom; gray, ethanol.

two neighbor Er ions are bridged through two μ−η1:η1 O−P− O moieties from two R-L ligands, leading to a head to tail arrangement of four Er(III) ions, forming a Er4 square core. In addition, four Er(III) ions are bridged via a μ4-η2:η2:η2:η2 PO43− anion, which also serves as a template anion (Figures 4, 5). The coordination sphere is completed by an ethanol (Er2− 4, Er6−8) or a water molecule (Er1, Er5). The Er4 square and the P atom of the template (P9, P18) locate on a plane (SI, Figure S5). The average intramolecular Er···Er distance for the neighbor Er(III) ions is 4.317(1) Å, and the one for the diagonal Er(III) ions is 6.104(1) Å (SI, Table S9). The packing of the crystal structure indicates that the shortest intermolecular Er···Er distance is 11.760(1) Å. Each Er ion is surrounded by seven O atoms, two from the PO43− anion, four from R-L ligands, and one from a coordination solvent ethanol/water molecule. SHAPE63 analyses reveal that the ligand arrangement leads to a distorted pentagonal bipyramid (D5h) as coordination polyhedron (Figure 5b and SI, Table S3). The average Er−O bond length is 2.304(18) Å, where the average bond length between Er and O atoms from the anionic R-L ligands (2.240(14) Å) is slightly shorter than the one from neutral ethanol/water ligands (2.304(18) Å), and the template anion PO43− (2.430 (12) Å) (SI, Table S8). For one pentagonal bipyramid, the pentagon plane contains two short bonds with R-L ligands and three long bonds with ethanol/water and PO43− template, while the apical bonds are both short with R-L ligands. Thus, the pentagonal bipyramid is not simply compressed or elongated along the axis but irregularly distorted. In this case, although the average apical bond length (2.220(13)) is slightly shorter than the equilateral one (2.337(18)), it could not conclude that the equilateral ligand field is weaker than the axial one because the number of short bonds on the pentagonal plane is the same as for the axial one. The ligands also maintain their R form as the starting free ligands. The torsion angle and dihedral angles of two benzenes or two naphthalenes of the complex R-2 are similar as the free ligand,and slightly larger (2−3°) than the ones for R-1 (SI, Figure S7 and Table S10). From the CCM calculations, the chirality of the metal centers is even more unobvious than R-1.

Figure 5. (a) Coordination environment of R-2. Color code: Er, green; O, red; P, violet. (b) Coordination polyhedra in R-2, illustrating four distorted pentagonal bipyramids.

The average CCM value for the first coordination sphere is 0.0776, and the one for the second coordination sphere is 0.895. While for the chiral ligands, the average CCM value is 6.08. These also indicate the chirality is mainly located on the chiral ligands. Magnetic Properties. Variable temperature direct-current (dc) magnetic susceptibility of R-1 (Figure 6) and R-2 (Figure 7) were measured on polycrystalline samples under a 0.1 T applied field. The χMT values of R-1 and R-2 at 300 K are

Figure 6. Temperature dependence of the χMT products for R-1 under a 0.1 T dc field. Inset: M vs H plot for R-1. The solid lines correspond to the ab initio calculations (scaled up by 1.0963). D

DOI: 10.1021/acs.inorgchem.9b00616 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

Figure 7. Temperature dependence of the χMT products for R-2 under a 0.1 T dc field. Inset: M vs H plot for R-2.

24.90 and 43.14 cm3 K mol−1, respectively, which are close to the expected theoretical values of 22.96 and 45.92 cm3 K mol−1 for two and four isolated Er(III) ions (4I15/2, S = 3/2, L = 6, gJ = 6/5), respectively. For R-1, the χMT product decreases gradually upon cooling from 300 K, reaching to a minimum value of 21.34 cm3 K mol−1 at 10 K, then rapidly increasing to a maximum value of 23.71 cm3 K mol−1 at 2 K. The gradual decrease above 10 K is mostly caused by the thermal depopulation of the excited mJ states of Er(III), whereas the rapid increase at low temperature could be attributed to ferromagnetic intramolecular dipolar interactions, which was confirmed by ab initio calculations and will be discussed vide infra. For R-2, the χMT product decrease gradually upon cooling to a minimum value of 19.66 cm3 K mol−1. This decrease is mainly due to the thermal depopulation of the excited mJ states of Er(III) and/or the magnetic interactions. The field dependence of magnetizations for R-1 and R-2 are shown in the inset of Figures 6 and 7, respectively. The magnetization at 7 T of 10.5 and 19.9 NμB for R-1 and R-2 are close to the of expected theoretical values of 9 and 18 NμB for two and four Er(III) ions (4I15/2, J = 15/2, gJ = 6/5), respectively. To investigate the magnetic dynamics of R-1 and R-2, temperature and frequency alternating-current (ac) magnetic susceptibilities were measured using polycrystalline sample with mother liquor. Under a zero applied magnetic field, R-1 shows a frequency dependence in the temperature ranges of 3−9 K (Figure 8a) which is a typical SMM behavior. R-2, however, shows no frequency dependence (SI, Figure S24). Under a 1000 Oe applied magnetic field, R-2 shows “tails” in temperature-dependent ac magnetic susceptibilities. However, no χM′′ maximum was observed (SI, Figure S25). For R-1, a small applied magnetic field could suppress the QTM, and this optimal magnetic field was found to be 800 Oe, after a scan field of the frequency dependence of the magnetic susceptibility (SI, Figures S14, S15). Under an 800 Oe field, the maximum of χM′′ shifts from 106 to 7 Hz at 3 K indicating a significant suppression of QTM after applying dc field (Figure 8a). Under both zero and 800 Oe field, R-1 shows two maxima of χM’’ (Figure 8), and Cole−Cole plots also indicate two relaxation processes (SI, Figures S20, S21). Therefore, in the temperature range of 3−5.7 K, two relaxation times τSR (slow relaxation) and τFR (fast relaxation) can be obtained by fitting the ac data with an extended Debye model containing two relaxation times. In the temperature range of 6−8 K, the

Figure 8. Frequency dependence (a) and temperature dependence (b) of out-of-phase χM′′ for R-1 under zero (up) and 800 Oe dc field (down). The solid lines are guides for the eyes.

second relaxation time τFR is too fast and out of our investigated frequency range, thus the ac data was fitted with a Debye model with one relaxation time (τSR). For S-1 and S-2, the ac magnetic susceptibilities were also performed under a zero field and applied magnetic field (SI, Figures S22−S25). No significant differences were observed when comparing with their enantiomers, which is also the case in literature.33 The Arrhenius plot of ln(τ) vs 1/T is shown in Figure 9. Different fitting attempts are listed in SI, Table S11, and displayed in SI, Figure S26, for τSR, and SI, Figure S27 for τFR, while the best fits are shown in Figure 9. Under an 800 Oe applied dc magnetic field, the ln(τFR) vs 1/T plot (red circle in Figure 9) is temperature dependent and relatively straight. Thus, we applied an Orbach relaxation process, τ−1 = τ0−1 exp(−Ueff/kBT), or a Raman process, τ−1 = CTn, to fit this line. The former one gives a better result with a larger adj R-square (0.99057 vs 0.97539). Thus, an energy barrier of Ueff/kB = 40(1) K and the pre-exponential factor τ0 = 2.1(5) × 10−8 s can be obtained from this fit. Under a zero field, the ln(τFR) vs 1/T plot (black circle in Figure 9) is also temperature dependent at high temperature, but a temperature-independent tendency is shown at low temperature. Thus, a simple Orbach process can not fit this curve. Using Orbach and QTM to fit this curve could give a satisfying result. In addition, the Ueff was set to be the same when fitting the ln(τFR) vs 1/T curves under a zero and an 800 Oe field simultaneously, giving τ0 = 1.2(3) × 10−8 s, τQTM = 8(1) × 10−4 s. E

DOI: 10.1021/acs.inorgchem.9b00616 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

both zero and applied magnetic field, Orbach and Raman dominate the relaxation. Under applied magnetic field, Raman also becomes slower with significant enhancement of n from 3.1 (zero field) to 5.9 (800 Oe field).68,69 Both interpretations are reasonable. We prefer the former one because the fitting requires fewer parameters which could effectively avoid overparameterizatiom. Moreover, the information on higher temperature is limited, hindering the verification of this Orbach process. Ab initio Calculations. To gain profound understanding of the magnetic dynamics of R-1, we performed ab initio calculations on R-1 whose hydrogen positions were optimized by DFT calculations (see computational details above). The main magnetic axes of Er1 and Er2 were calculated and presented in Figure 10. They are not parallel with an angle of Figure 9. Temperature dependence of the relaxation time τSR (square) and τFR (circle) under zero (black) and 800 Oe dc magnetic field (red) for R-1 in the temperature range of 3−8 K. The lines are the best fits.

To explore other possible fittings, we tried a simultaneous fitting of the curves with and without field using Orbach and Orbach plus Raman, respectively, sharing the same Ueff. However, this fitting gives an n value of the Raman term close to zero, which indicates this term is temperature-independent and can be described as QTM. We also tried Raman and QTM for the zero field data, giving n = 10.1(5), which exceeds the normal Raman range (1−6).66,67 This result indicates that, for τFR, Orbach and QTM dominate the relaxation under a zero field, and the QTM could be suppressed by the applied magnetic field. Under an 800 Oe field, the ln(τSR) vs 1/T plot (red square in Figure 9) is temperature dependent but not straight. Thus, a single Orbach relaxation process could not fit this curve. The combination of Orbach and QTM or Orbach and direct processes also could not give satisfying results (adj R-square = 0.98354, 0.98938, respectively), while a Raman process gives a good fit with C = 0.017(4) s−1 K−n, n = 6.7(1). Meanwhile, a fitting using Orbach and Raman τ−1 = τ0−1exp(−Ueff/kBT) + CTn could also fit this curve, giving Ueff = 82(9) K, τ0 = 3(3) × 10−9 s, C = 0.04(1) s−1 K−n, n = 5.9(2). Under a zero field, the ln(τSR) vs 1/T plot (black square in Figure 9) is more curved at low temperature. Thus, a single Orbach or Raman relaxation process could not fit this curve, nor does the combination of Orbach and QTM (adj R-square = 0.9066, 0.96951, 0.98354, respectively), while, a fitting using Raman and QTM, τ−1 = CTn + τQTM−1, can fit this curve, giving C = 0.5(2) s−1 K−n, n = 5.1(2), τQTM = 2.7(4) × 10−3 s. As under an 800 Oe field, a fitting using Orbach and Raman could also fit the curve, giving Ueff = 82(9) K, τ0 = 2(3) × 10−9 s, C = 14(2) s−1 K−n, n = 3.1(1). This Ueff was set to be the same when fitting the ln(τSR) vs 1/T curves under a zero and an 800 Oe field simultaneously. To avoid overparameterization, the combination of three processes was not applied to fit these curves. The above fitting suggests two possible interpretations for τSR under a zero and an 800 Oe field. One interpretation is that, under a zero field, Raman, and QTM dominate the relaxation. Under applied magnetic field, QTM is suppressed and Raman relaxation slightly slows down with enhanced n from 5.1 (zero field) to 6.7 (800 Oe field).68,69 The other interpretation is that, under

Figure 10. Green arrow represents the orientation of the main magnetic axes of the ground Kramers doublet obtained from the ab initio calculations. Color codes: Er, green; O, red; P, violet; C, gray.

35.2° and are approximately along the Er1−Er2 direction with deviations of 27.6° and 14.9° for Er1 and Er2, respectively. The energy of the magnetic dipolar interaction is relative to these angles and the distance between the two ions: μ0 1 Edip = − [3(μi⃗ ·uij⃗ )uij⃗ − μi⃗ ]·μj⃗ 4π rij3 (1)

{ }

where μ⃗i and μ⃗j are the magnetic moments from each ion, and uij⃗ and rij are the unit vector and the distance between the two ions.70 The intramolecular dipolar interaction is calculated with eq 1, giving ΔE↑↓−↑↑ = 1.12 cm−1, thus E↑↑ < E↑↓, indicating a ferromagnetic dipolar interaction. This is in agreement with the deduction from eq 1 that ferromagnetic dipolar interaction will be found when the angles between the magnetic axes and the vector of the two ions are smaller than 54.75°,11,70,71 which in this case are 27.6° and 14.9° (Figure 10). The calculated magnetic susceptibilities and magnetization are in good agreement with the experiment upon applying only this dipolar interaction between the Er(III) ions (Figure 6). Slow magnetic relaxations of Er(III) usually result from the equatorial ligand field.10,11 To verify whether R-1 possesses an F

DOI: 10.1021/acs.inorgchem.9b00616 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry equatorial or axial ligand field, we measured the zenith angles θ (Figure 1a) for all ligands (SI, Table S7). The average θ of the anionic chiral ligands, 63.8°, is larger than the “magic angle” 54.7°, which means these anionic chiral ligands provide the equatorial ligand field,10 while one of the neutral ethanol ligands, 49.9°, is smaller than the “magic angle” and thus providing an axial ligand field.10 This result is in agreement with the crystal structure of R-1 that the chiral ligands have larger O-Ln-O angles than the ethanol ligands (Figure 3a, SI, Table S6). Thus, different types of ligand fields are found in the chiral ligands and the ethanol ligands. However, we could still qualitatively conclude that the overall ligand field of R-1 is equatorial because (1) the chiral ligands provide four O atoms for each Er(III), which is more than the three neutral ethanol ligands, (2) the chiral ligands are anionic while the ethanol ligands are neutral, (3) the O−Er bond length of the chiral ligands are shorter than the ethanol ligands (SI, Table S5), and from these points, the chiral ligands should provide more contributions for the ligand field than the ethanol ligands, and (4) the difference between the average θ of the chiral ligands and the “magic angle”, 9.1°, is larger than the one of the ethanol ligands, 4.8°, thus the equatorial ligand field of the chiral ligands should be stronger than the axial ligand field of the ethanol ligands. This is also evidenced by the calculated main wave function composition of the ground Kramers doublet (KD), which is mJ = ±15/2 (SI, Table S12), by the reason that the mJ state, whose magnetic moment is maximized (J = ±15/2), is stabilized as the ground state when the ligand field is equatorial for the prolate Ln(III) ions. Thus, the prolate Er(III) ions with equatorial ligand field lead to high anisotropy (gZ ≫ gx, gy, Table 1) and the observed slow magnetic relaxations.

excited KD energies are different from the experimental energy barrier (27, 57 cm−1), indicating that the relaxation pathway might be other than an Orbach process. Circular Dichroism (CD) Spectra. The chirality of R-HL, S-HL, R-1, S-1, R-2, and R-1 is studied by their circular dichroism (CD) spectra (Figure 11). S-HL shows positive

Figure 11. Solid-state CD spectra of R-HL, S-HL, R-1, S-1, R-2, and S-2 in the KCl matrix at room temperature.

Cotton effects at 232 and 264 nm, with anisotropic dissymmetry factor72 gabs = ΔA/A = 1.2 × 10−3 and 2.1 × 10−3, respectively. Two negative Cotton effects were observed at 200 (gabs = −1.3 × 10−3) and 332 (gabs = −1.2 × 10−3) nm. S-1 and S-2 exhibit similar CD spectra as the ligand. S-1 shows a weaker positive peak at 234 nm (gabs = 2.1 × 10−4), a stronger positive peak at 266 nm (gabs = 1.2 × 10−3), and smaller negative signals at around 205 (gabs = −6.2 × 10−5) and 329 (gabs = −2.4 × 10−6) nm when comparing with the ligand S-HL. S-2 also shows a weaker positive peak at 232 (gabs = 2.4 × 10−4), a similar positive peak at 267 (gabs = 6.4 × 10−4) nm, and a weaker negative peak at 334 (gabs = −1.9 × 10−4) nm when comparing with the ligand S-HL. These signals are relative to the π−π* transition of the chiral ligands, as strong UV absorption are observed for the complexes (SI, Figures S28, S29). As the CD spectra of the coordinated complexes are similar to the chiral ligands, the CD signals from the complexes should be dominated by the ligands. This is also suggested by the above-mentioned CCM calculations indicating the chirality from the metal centers is negligible comparing with the chiral ligands, while the small discrepancy between these compounds might be due to the inductive charge between Er3+ and H+ and/or the different torsion and dihedral angles (SI, Table S10); although a slightly low signal at around 330 nm for S-2 is observed, the CD spectra of the enantiomers approximately show mirror images indicating their enantiomeric nature.

Table 1. Ab Initio Calculated g-Tensors and Energies of the Lowest Two Kramers Doublets for Er1 and Er2 of R-1 KD

E (cm−1)

gX

gY

gZ

Er1

1 2

0 70.3

0.0676 2.2550

0.1438 5.6878

16.9905 10.5443

Er2

1 2

0 51.0

0.1397 1.1901

0.2515 2.0870

16.4224 12.4963

The above multirelaxation process could be caused by multirelaxation pathways or/and crystallographically different Er ions, Er1 and Er2 in R-1. To figure out the origin of the multirelaxation process, we compared the anisotropy, the energy of mJ states, and the magnetic axes of Er1 and Er2. The two Er(III) ions are found to be highly anisotropic in the ground KD, with large axial components, gZ = 16.9905 and 16.4224 for Er1 and Er2, respectively (SI, Table 1, Table S12). For the first excited KD, Er2 shows stronger axial components (gZ = 12.4963) and weaker transverse components than those of Er1 (gZ = 10.5443) (Table 1). However, the energies of the first excited KDs on Er1 (70.3 cm−1) is higher than Er2 (51.0 cm−1). In addition, the calculated main magnetic axes of Er1 and Er2 are not parallel with an angle of 35.2° (Figure 10). Given the above, deviations are found in g-tensors and the energy of the first excited KDs and the magnetic axis on the two Er(III) ions. Thus, the observed multirelaxation behavior might be attributed to the crystallographical difference of Er1 and Er2, although it is difficult to identify the original Er(III) ions for the two relaxations. Moreover, the calculated first

■

CONCLUSIONS In conclusion, a chiral Er-based SMM was achieved through coordination of the chiral ligand binaphthyl phosphate. For dinuclear complex R-1, the ligand arrangement leads to an overall equatorial ligand field for the Er(III) ions, which is suitable for the prolate Er(III) to construct SMMs. It exhibits two magnetic relaxation pathways under a zero field. One consists of a QTM process and a thermal-active relaxation with an apparent barrier of 40 K. The other comprises a Raman and a QTM processes or a Raman and a thermal-active relaxation process with an apparent barrier of 82 K. The QTM can be suppressed by an 800 Oe dc magnetic field. Ab initio calculations suggest that there is a ferromagnetic intramolecular dipolar interaction, the ligand field is equatorial, G

DOI: 10.1021/acs.inorgchem.9b00616 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

(7) Randall McClain, K.; Gould, C. A.; Chakarawet, K.; Teat, S. J.; Groshens, T. J.; Long, J. R.; Harvey, B. G. High-temperature magnetic blocking and magneto-structural correlations in a series of dysprosium(III) metallocenium single-molecule magnets. Chem. Sci. 2018, 9 (45), 8492−8503. (8) 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. (9) Guo, F.-S.; Day, B. M.; Chen, Y.-C.; Tong, M.-L.; Mansikkamäki, A.; Layfield, R. A. A Dysprosium Metallocene Single-Molecule Magnet Functioning at the Axial Limit. Angew. Chem., Int. Ed. 2017, 56 (38), 11445−11449. (10) Rinehart, J. D.; Long, J. R. Exploiting single-ion anisotropy in the design of f-element single-molecule magnets. Chem. Sci. 2011, 2 (11), 2078−2085. (11) Liu, J.-L.; Chen, Y.-C.; Tong, M.-L. Symmetry strategies for high performance lanthanide-based single-molecule magnets. Chem. Soc. Rev. 2018, 47 (7), 2431−2453. (12) Zhang, P.; Zhang, L.; Wang, C.; Xue, S. F.; Lin, S.-Y.; Tang, J. Equatorially Coordinated Lanthanide Single Ion Magnets. J. Am. Chem. Soc. 2014, 136 (12), 4484−4487. (13) Brown, A. J.; Pinkowicz, D.; Saber, M. R.; Dunbar, K. R. A Trigonal-Pyramidal Erbium(III) Single-Molecule Magnet. Angew. Chem., Int. Ed. 2015, 54 (20), 5864−5868. (14) Zhang, P.; Jung, J.; Zhang, L.; Tang, J.; Le Guennic, B. Elucidating the Magnetic Anisotropy and Relaxation Dynamics of Low-Coordinate Lanthanide Compounds. Inorg. Chem. 2016, 55 (4), 1905−1911. (15) Jiang, S.-D.; Wang, B.-W.; Sun, H.-L.; Wang, Z.-M.; Gao, S. An Organometallic Single-Ion Magnet. J. Am. Chem. Soc. 2011, 133 (13), 4730−4733. (16) Meihaus, K. R.; Long, J. R. Magnetic Blocking at 10 K and a Dipolar-Mediated Avalanche in Salts of the Bis(η8-cyclooctatetraenide) Complex [Er(COT)2]−. J. Am. Chem. Soc. 2013, 135 (47), 17952−17957. (17) Le Roy, J. J.; Korobkov, I.; Murugesu, M. A sandwich complex with axial symmetry for harnessing the anisotropy in a prolate erbium(III) ion. Chem. Commun. 2014, 50 (13), 1602−1604. (18) Ungur, L.; Le Roy, J. J.; Korobkov, I.; Murugesu, M.; Chibotaru, L. F. Fine-tuning the Local Symmetry to Attain Record Blocking Temperature and Magnetic Remanence in a Single-Ion Magnet. Angew. Chem., Int. Ed. 2014, 53 (17), 4413−4417. (19) Meng, Y.-S.; Wang, C.-H.; Zhang, Y.-Q.; Leng, X.-B.; Wang, B.W.; Chen, Y.-F.; Gao, S. (Boratabenzene)(cyclooctatetraenyl) lanthanide complexes: a new type of organometallic single-ion magnet. Inorg. Chem. Front. 2016, 3 (6), 828−835. (20) Chen, S.-M.; Xiong, J.; Zhang, Y.-Q.; Yuan, Q.; Wang, B.-W.; Gao, S. A soft phosphorus atom to “harden” an erbium(III) single-ion magnet. Chem. Sci. 2018, 9 (38), 7540−7545. (21) Rikken, G. L. J. A.; Raupach, E. Observation of magneto-chiral dichroism. Nature 1997, 390 (6659), 493−494. (22) Bogani, L.; Cavigli, L.; Bernot, K.; Sessoli, R.; Gurioli, M.; Gatteschi, D. Evidence of intermolecular π-stacking enhancement of second-harmonic generation in a family of single chain magnets. J. Mater. Chem. 2006, 16 (26), 2587−2592. (23) Zhang, W.; Xiong, R.-G. Ferroelectric Metal−Organic Frameworks. Chem. Rev. 2012, 112 (2), 1163−1195. (24) Li, D.-P.; Wang, T.-W.; Li, C.-H.; Liu, D.-S.; Li, Y.-Z.; You, X.Z. Single-ion magnets based on mononuclear lanthanide complexes with chiral Schiff base ligands [Ln(FTA)3L] (Ln = Sm, Eu, Gd, Tb and Dy). Chem. Commun. 2010, 46 (17), 2929−2931. (25) Li, X.-L.; Chen, C.-L.; Gao, Y.-L.; Liu, C.-M.; Feng, X.-L.; Gui, Y.-H.; Fang, S.-M. Modulation of Homochiral DyIII Complexes: Single-Molecule Magnets with Ferroelectric Properties. Chem. - Eur. J. 2012, 18 (46), 14632−14637. (26) Liu, J.; Zhang, X.-P.; Wu, T.; Ma, B.-B.; Wang, T.-W.; Li, C.-H.; Li, Y.-Z.; You, X.-Z. Solvent-Induced Single-Crystal-to-Single-Crystal Transformation in Multifunctional Chiral Dysprosium(III) Compounds. Inorg. Chem. 2012, 51 (16), 8649−8651.

and the multirelaxation process might be caused by the crystallographically different Er(III) ions. With a template effect, the tetranuclear complexes R-2 and S-2 were obtained. Thus, we demonstrate an example of chiral Er-SMM and a nuclearity control with template effect.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.9b00616. Crystallographic data, selected bond lengths and angles, shape and CCM analysis, thermogravimetric analysis, powder X-ray diffraction patterns, additional magnetic data, UV−vis−NIR absorption, and computational details (PDF) Accession Codes

CCDC 1900543−1900546 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge 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.

■

AUTHOR INFORMATION

Corresponding Authors

*M.-L.T.: E-mail, [email protected]. *M.F.: E-mail, [email protected]. ORCID

Yan-Cong Chen: 0000-0001-5047-3445 Jun-Liang Liu: 0000-0002-5811-6300 Ming-Liang Tong: 0000-0003-4725-0798 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was supported by the China Postdoctoral Science Foundation (2018M633208), the National Key Research and Development Program of China (2018YFA0306001), the NSFC (grant nos. 21620102002, 21822508, 21701198, and 21821003), and the Pearl River Talent Plan of Guangdong (2017BT01C161).

■

REFERENCES

(1) Sessoli, R.; Gatteschi, D.; Caneschi, A.; Novak, M. A. Magnetic bistability in a metal-ion cluster. Nature 1993, 365, 141−143. (2) 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. (3) Pedersen, K. S.; Ariciu, A.-M.; McAdams, S.; Weihe, H.; Bendix, J.; Tuna, F.; Piligkos, S. Toward Molecular 4f Single-Ion Magnet Qubits. J. Am. Chem. Soc. 2016, 138 (18), 5801−5804. (4) Rocha, A. R.; García-suárez, V. M.; Bailey, S. W.; Lambert, C. J.; Ferrer, J.; Sanvito, S. Towards molecular spintronics. Nat. Mater. 2005, 4, 335−339. (5) Vincent, R.; Klyatskaya, S.; Ruben, M.; Wernsdorfer, W.; Balestro, F. Electronic read-out of a single nuclear spin using a molecular spin transistor. Nature 2012, 488, 357. (6) Guo, F.-S.; Day, B. M.; Chen, Y.-C.; Tong, M.-L.; Mansikkamäki, A.; Layfield, R. A. Magnetic hysteresis up to 80 K in a dysprosium metallocene single-molecule magnet. Science 2018, 362 (6421), 1400−1403. H

DOI: 10.1021/acs.inorgchem.9b00616 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry

metric Aza-Diels−Alder Reactions of Cyclic Ketones. J. Org. Chem. 2015, 80 (16), 7984−7993. (43) Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.; Puschmann, H. OLEX2: a complete structure solution, refinement and analysis program. J. Appl. Crystallogr. 2009, 42 (2), 339−341. (44) Sheldrick, G. A short history of SHELX. Acta Crystallogr., Sect. A: Found. Crystallogr. 2008, 64 (1), 112−122. (45) Sheldrick, G. SHELXT - Integrated space-group and crystalstructure determination. Acta Crystallogr., Sect. A: Found. Adv. 2015, 71 (1), 3−8. (46) Sheldrick, G. Crystal structure refinement with SHELXL. Acta Crystallogr., Sect. C: Struct. Chem. 2015, C71, 3−8. (47) Spek, A. PLATON SQUEEZE: a tool for the calculation of the disordered solvent contribution to the calculated structure factors. Acta Crystallogr., Sect. C: Struct. Chem. 2015, 71 (1), 9−18. (48) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77 (18), 3865− 3868. (49) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple [Phys. Rev. Lett. 77, 3865 (1996)]. Phys. Rev. Lett. 1997, 78 (7), 1396−1396. (50) Weigend, F.; Ahlrichs, R. Balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for H to Rn: Design and assessment of accuracy. Phys. Chem. Chem. Phys. 2005, 7 (18), 3297−3305. (51) Schäfer, A.; Horn, H.; Ahlrichs, R. Fully optimized contracted Gaussian basis sets for atoms Li to Kr. J. Chem. Phys. 1992, 97 (4), 2571−2577. (52) Neese, F. The ORCA program system. WIREs Comput. Mol. Sci. 2012, 2 (1), 73−78. (53) Neese, F. Software update: the ORCA program system, version 4.0. WIREs Comput. Mol. Sci. 2018, 8 (1), e1327. (54) Aquilante, F.; Autschbach, J.; Carlson, R. K.; Chibotaru, L. F.; Delcey, M. G.; De Vico, L.; Fdez. Galván, I.; Ferré, N.; Frutos, L. M.; Gagliardi, L.; Garavelli, M.; Giussani, A.; Hoyer, C. E.; Li Manni, G.; Lischka, H.; Ma, D.; Malmqvist, P. Å.; Müller, T.; Nenov, A.; Olivucci, M.; Pedersen, T. B.; Peng, D.; Plasser, F.; Pritchard, B.; Reiher, M.; Rivalta, I.; Schapiro, I.; Segarra-Martí, J.; Stenrup, M.; Truhlar, D. G.; Ungur, L.; Valentini, A.; Vancoillie, S.; Veryazov, V.; Vysotskiy, V. P.; Weingart, O.; Zapata, F.; Lindh, R. Molcas 8: New capabilities for multiconfigurational quantum chemical calculations across the periodic table. J. Comput. Chem. 2016, 37 (5), 506−541. (55) Roos, B. O.; Lindh, R.; Malmqvist, P.-Å.; Veryazov, V.; Widmark, P.-O.; Borin, A. C. New Relativistic Atomic Natural Orbital Basis Sets for Lanthanide Atoms with Applications to the Ce Diatom and LuF3. J. Phys. Chem. A 2008, 112 (45), 11431−11435. (56) Roos, B. O.; Lindh, R.; Malmqvist, P.-Å.; Veryazov, V.; Widmark, P.-O. Main group atoms and dimers studied with a new relativistic ANO basis set. J. Phys. Chem. A 2004, 108 (15), 2851− 2858. (57) Roos, B. O.; Lindh, R.; Malmqvist, P.-Å.; Veryazov, V.; Widmark, P.-O. New relativistic ANO basis sets for transition metal atoms. J. Phys. Chem. A 2005, 109 (29), 6575−6579. (58) Malmqvist, P.-Å.; Roos, B. O.; Schimmelpfennig, B. The restricted active space (RAS) state interaction approach with spin− orbit coupling. Chem. Phys. Lett. 2002, 357 (3), 230−240. (59) Chibotaru, L. F.; Ungur, L. Ab initio calculation of anisotropic magnetic properties of complexes. I. Unique definition of pseudospin Hamiltonians and their derivation. J. Chem. Phys. 2012, 137 (6), 064112. (60) Chibotaru, L. F.; Ungur, L.; Soncini, A. The Origin of Nonmagnetic Kramers Doublets in the Ground State of Dysprosium Triangles: Evidence for a Toroidal Magnetic Moment. Angew. Chem., Int. Ed. 2008, 47 (22), 4126−4129. (61) Ungur, L.; Van den Heuvel, W.; Chibotaru, L. F. Ab initio investigation of the non-collinear magnetic structure and the lowest magnetic excitations in dysprosium triangles. New J. Chem. 2009, 33 (6), 1224−1230.

(27) Li, X.-L.; Chen, C.-L.; Xiao, H.-P.; Wang, A.-L.; Liu, C.-M.; Zheng, X.; Gao, L.-J.; Yang, X.-G.; Fang, S.-M. Luminescent, magnetic and ferroelectric properties of noncentrosymmetric chain-like complexes composed of nine-coordinate lanthanide ions. Dalton Trans. 2013, 42 (43), 15317−15325. (28) Ou-Yang, J.-K.; Saleh, N.; Fernandez Garcia, G.; Norel, L.; Pointillart, F.; Guizouarn, T.; Cador, O.; Totti, F.; Ouahab, L.; Crassous, J.; Le Guennic, B. Improved slow magnetic relaxation in optically pure helicene-based DyIII single molecule magnets. Chem. Commun. 2016, 52 (100), 14474−14477. (29) Fernandez-Garcia, G.; Flores Gonzalez, J.; Ou-Yang, J.-K.; Saleh, N.; Pointillart, F.; Cador, O.; Guizouarn, T.; Totti, F.; Ouahab, L.; Crassous, J.; Le Guennic, B. Slow Magnetic Relaxation in Chiral Helicene-Based Coordination Complex of Dysprosium. Magnetochemistry 2017, 3 (1), 2. (30) Li, X.-L.; Hu, M.; Yin, Z.; Zhu, C.; Liu, C.-M.; Xiao, H.-P.; Fang, S. Enhanced single-ion magnetic and ferroelectric properties of mononuclear Dy(III) enantiomeric pairs through the coordination role of chiral ligands. Chem. Commun. 2017, 53 (28), 3998−4001. (31) Pointillart, F.; Ou-Yang, J.-K.; Fernandez Garcia, G.; Montigaud, V.; Flores Gonzalez, J.; Marchal, R.; Favereau, L.; Totti, F.; Crassous, J.; Cador, O.; Ouahab, L.; Le Guennic, B. Tetrathiafulvalene-Based Helicene Ligand in the Design of a Dysprosium Field-Induced Single-Molecule Magnet. Inorg. Chem. 2019, 58 (1), 52−56. (32) Li, D.-P.; Zhang, X.-P.; Wang, T.-W.; Ma, B.-B.; Li, C.-H.; Li, Y.-Z.; You, X.-Z. Distinct magnetic dynamic behavior for two polymorphs of the same Dy(III) complex. Chem. Commun. 2011, 47 (24), 6867−6869. (33) Liu, C.-M.; Zhang, D.-Q.; Zhu, D.-B. Field-Induced Single-Ion Magnets Based on Enantiopure Chiral β-Diketonate Ligands. Inorg. Chem. 2013, 52 (15), 8933−8940. (34) Wada, H.; Ooka, S.; Iwasawa, D.; Hasegawa, M.; Kajiwara, T. Slow Magnetic Relaxation of Lanthanide(III) Complexes with a Helical Ligand. Magnetochemistry 2016, 2 (4), 43. (35) Feng, M.; Tong, M.-L. Single Ion Magnets from 3d to 5f: Developments and Strategies. Chem. - Eur. J. 2018, 24 (30), 7574− 7594. (36) Zaleski, C. M.; Depperman, E. C.; Kampf, J. W.; Kirk, M. L.; Pecoraro, V. L. Using LnIII[15-MCCuII(N)(S)-pheHA-5]3+ Complexes To Construct Chiral Single-Molecule Magnets and Chains of Single-Molecule Magnets. Inorg. Chem. 2006, 45 (25), 10022−10024. (37) Inglis, R.; White, F.; Piligkos, S.; Wernsdorfer, W.; Brechin, E. K.; Papaefstathiou, G. S. Chiral single-molecule magnets: a partial Mn(III) supertetrahedron from achiral components. Chem. Commun. 2011, 47 (11), 3090−3092. (38) Long, J.; Rouquette, J.; Thibaud, J.-M.; Ferreira, R. A. S.; Carlos, L. D.; Donnadieu, B.; Vieru, V.; Chibotaru, L. F.; Konczewicz, L.; Haines, J.; Guari, Y.; Larionova, J. A High-Temperature Molecular Ferroelectric Zn/Dy Complex Exhibiting Single-Ion-Magnet Behavior and Lanthanide Luminescence. Angew. Chem., Int. Ed. 2015, 54 (7), 2236−2240. (39) Novitchi, G.; Pilet, G.; Ungur, L.; Moshchalkov, V. V.; Wernsdorfer, W.; Chibotaru, L. F.; Luneau, D.; Powell, A. K. Heterometallic CuII/DyIII 1D chiral polymers: chirogenesis and exchange coupling of toroidal moments in trinuclear Dy3 single molecule magnets. Chem. Sci. 2012, 3 (4), 1169−1176. (40) Novitchi, G.; Pilet, G.; Luneau, D. Chiral single-molecule magnet with a 35K energy barrier for relaxation of the magnetization. C. R. Chim. 2012, 15 (10), 937−942. (41) Pedziwiatr, M.; Kosareff, N. M.; Muller, G.; Koposov, A. Y.; Nemykin, V. N.; Riehl, J. P.; Legendziewicz, J. Preparation, characterization, and circularly polarized luminescence of lanthanum and europium 1,1′-binaphthyl-2,2′-diyl phosphate complexes. J. Alloys Compd. 2008, 451 (1), 251−253. (42) Deng, Y.; Karunaratne, C. V.; Csatary, E.; Tierney, D. L.; Wheeler, K.; Wang, H. Chiral Bimetallic Catalysts Derived from Chiral Metal Phosphates: Enantioselective Three-Component AsymI

DOI: 10.1021/acs.inorgchem.9b00616 Inorg. Chem. XXXX, XXX, XXX−XXX

Article

Inorganic Chemistry (62) Chibotaru, L. F.; Ungur, L.; Aronica, C.; Elmoll, H.; Pilet, G.; Luneau, D. Structure, Magnetism, and Theoretical Study of a MixedValence CoII3CoIII4 Heptanuclear Wheel: Lack of SMM Behavior despite Negative Magnetic Anisotropy. J. Am. Chem. Soc. 2008, 130 (37), 12445−12455. (63) Llunell, M.; Casanova, D.; Cirera, J.; Alemany, P.; Alvarez, S. SHAPE, version 2.1; Electronic Structure Group, University of Barcelona: Barcelona, 2013. (64) Fujii, I.; Hirayama, N. Chiral Space Formed by (+)-(1S)-1,1′Binaphthalene-2,2′-diyl Phosphate: Recognition of Aliphatic L-αAmino Acids. Helv. Chim. Acta 2002, 85 (9), 2946−2960. (65) Alvarez, S.; Alemany, P.; Avnir, D. Continuous chirality measures in transition metal chemistry. Chem. Soc. Rev. 2005, 34 (4), 313−326. (66) Singh, A.; Shrivastava, K. N. Optical-acoustic two-phonon relaxation in spin systems. Phys. Status Solidi B 1979, 95 (1), 273− 277. (67) Shrivastava, K. N. Theory of Spin−Lattice Relaxation. Phys. Status Solidi B 1983, 117 (2), 437−458. (68) Van Vleck, J. H. Paramagnetic Relaxation Times for Titanium and Chrome Alum. Phys. Rev. 1940, 57 (5), 426−447. (69) Orbach, R. Spin-Lattice Relaxation in Rare-Earth Salts: Field Dependence of the Two-Phonon Process. Proc. R. Soc. London A 1961, 264 (1319), 485−495. (70) Panissod, P.; Drillon, M. In Magnetism Molecules to Materials IV; Miller, J. S., Drillon, M., Ed.; Wiley-VCH Verlag GmbH & Co. KGaA, 2002; Chapter 7, p 325. (71) Leng, J.-D.; Liu, J.-L.; Lin, W.-Q.; Gómez-Coca, S.; Aravena, D.; Ruiz, E.; Tong, M.-L. Unprecedented ferromagnetic dipolar interaction in a dinuclear holmium(III) complex: a combined experimental and theoretical study. Chem. Commun. 2013, 49 (81), 9341−9343. (72) Wakabayashi, M.; Yokojima, S.; Fukaminato, T.; Shiino, K.-i.; Irie, M.; Nakamura, S. Anisotropic Dissymmetry Factor, g: Theoretical Investigation on Single Molecule Chiroptical Spectroscopy. J. Phys. Chem. A 2014, 118 (27), 5046−5057.

J

DOI: 10.1021/acs.inorgchem.9b00616 Inorg. Chem. XXXX, XXX, XXX−XXX