Syntheses, Structure, and Magnetic Properties of ... - ACS Publications

May 4, 2015 - ... center of a honeycomb framework forming a triangle lattice. Magnetic measurements reveal that the isostructural Ln2Cu(SO4)2(OH)4 exh...
0 downloads 0 Views 2MB Size
Download PDF
Article pubs.acs.org/crystal

Syntheses, Structure, and Magnetic Properties of New 3d−4f Heterometallic Hydroxysulfates Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, Tb, or Dy) with a Two-Dimensional Triangle Network Yingying Tang,†,§ Meiyan Cui,†,§ Wenbin Guo,† Suyun Zhang,† Ming Yang,† and Zhangzhen He*,†,‡ †

State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, P. R. China ‡ Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, P. R. China § University of the Chinese Academy of Sciences, Beijing 100039, P. R. China S Supporting Information *

ABSTRACT: A series of 3d−4f hydroxysulfates Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, Tb, or Dy) have been successfully obtained by the conventional hydrothermal method. These compounds crystallize in the monoclinic system in space group P21/c, showing a layered structure. The layers are built by the LnO9 polyhedra and CuO4 planar squares, which are separated by SO42− tetrahedra. The topological structure of Sm3+ ions shows a distorted honeycomb lattice, while Cu2+ ions are located at the center of a honeycomb framework forming a triangle lattice. Magnetic measurements reveal that the isostructural Ln2Cu(SO4)2(OH)4 exhibits different magnetic behaviors at low temperatures, which may be attributed to the different contribution of 3d−4f couplings.

■

INTRODUCTION Hydroxysulfates have attracted much attention in the past several decades, because of their various potential applications such as cathode materials,1 porosity,2 and magnetic properties.3 Current interest in hydroxysulfates mainly focuses on transition-metal or rare-earth-metal systems. For transitionmetal hydroxysulfates, their structures and magnetic properties have been investigated intensively. For example, antlerite Cu3(OH)4(SO4) features a three-legged ribbon structure built by edge-sharing copper octahedra, behaving as a low-dimensional antiferromagnet with a small spin-canting. 4 Co5(OH)6(SO4)2(H2O)4 is composed of edge-sharing Co− OH octahedral layers and exhibits ferromagnetic behavior with a Curie temperature of 14 K.5 Both Na2Co3(OH)2(SO4)3(H2O)4 and Co3(OH)2(HSO4)2(SO4)(H2O)4 show a helical Co3(OH)2 ferrimagnetic chain structure, exhibiting unusual slow magnetic relaxation behaviors.6 For rare-earth-metal hydroxysulfates, the investigations focus on a lanthanide contraction effect and a magnetocaloric effect (MCE). For example, a series of compounds Ln(OH)(SO4) (Ln = Pr−Yb) exhibit a three-dimensional (3D) framework composed of Ln3+ polyhedra, showing a remarkable lanthanide contraction effect.7 Usually, the coexistence of lanthanides and 3d transitionmetal ions in a compound may lead to rich structural chemistry and magnetic phenomena, because the diversity of coordinated environments of lanthanide and transition-metal ions will affect © XXXX American Chemical Society

structural frameworks and magnetic exchanges. Also, the buried 4f electrons of lanthanides would have a smaller crystal-field effect than 3d transition-metal ions in the compounds. Therefore, the large spin−orbit coupling, single-ion anisotropy, unquenched orbital angular momentum, and large spin values of lanthanides ions may induce various interesting and complicated magnetic behaviors in 3d−4f metal-based compounds. These have been confirmed in many 3d−4f systems such as Na2GdMnO(AsO4)28 and Sr3HoCrO6.9,10 Although 3d−4f systems have been studied intensively, hydroxysulfates containing lanthanides and a 3d transition metal are very rare; only YM(OH)3(SO4) (M = Cu or Ni)11,12 and Ce13Cr(HSO4)6(SO4)21(H2O)7513 have been reported. Recently, we have successfully synthesized new transitionmetal hydroxysulfates by a hydrothermal reaction, i.e., M3(TeO3)(SO4)(OH)2·2H2O (M = Ni or Co).14 In this work, we synthesized a series of new 3d−4f hydroxysulfates Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, Tb, or Dy) by introducing lanthanide ions into transition-metal hydroxysulfates. Herein, we report on the discovery of a series of new 3d−4f hydroxysulfates Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, Tb, or Dy). Further, the structural features and magnetic behaviors are also investigated. Received: January 14, 2015 Revised: March 20, 2015

A

DOI: 10.1021/acs.cgd.5b00057 Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

Table 1. Crystal Data and Structural Refinement Data for Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, Tb, or Dy) formula fw T, K λ, Å space group a, Å b, Å c, Å α, deg β, deg γ, deg V, Å3 Z Dcalcd, g cm−3 μ, cm−1 maximum and minimum transmissions GOF on F2 R1, wR2a R1, wR2 (all data) a

Sm2Cu(SO4)2(OH)4 624.44 room temperature 0.71073 P21/c 6.393(3) 6.792(3) 10.845(5) 90 98.616(9) 90 465.6(4) 2 4.454 152.22 1.0000, 0.6633 0.999 0.0229, 0.0582 0.0269, 0.0611

Eu2Cu(SO4)2(OH)4 627.66 room temperature 0.71073 P21/c 6.369(3) 6.760(3) 10.820(4) 90 98.600(9) 90 460.6(3) 2 4.526 162.05 1.000, 0.7136 1.077 0.0203, 0.0551 0.0225, 0.0566

Tb2Cu(SO4)2(OH)4 641.58 room temperature 0.71073 P21/c 6.321(2) 6.693(2) 10.757(4) 90 98.533(7) 90 450.1(3) 2 4.734 184.12 1.0000, 0.6558 1.019 0.0220, 0.0557 0.0243, 0.0567

Dy2Cu(SO4)2(OH)4 646.67 room temperature 0.71073 P21/c 6.304(4) 6.663(4) 10.724(6) 90 98.527(1) 90 445.5(5) 2 4.806 194.99 1.0000, 0.5156 1.134 0.0359, 0.0955 0.0397, 0.0990

R1 = ∑||F0| − |Fc||/∑|F0|, and wR2 = [∑w(F02 − Fc2)2/∑w(F02)2]1/2.

Figure 1. View of the oxygen coordination environments for (a) Sm, (b) Cu, and (c) S atoms.

■

report only its structure here. It must be noted that we cannot synthesize single crystals of Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, Tb, or Dy) in the absence of K2TeO3 and H3BO3, indicating that such additions may play important roles as mineralizers in the process of hydrothermal reaction. X-ray Crystallographic Studies. The small crystals of Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, Tb, or Dy) (∼0.15 mm × 0.15 mm × 0.05 mm) were selected and mounted on glassy fibers for single-crystal X-ray diffraction (XRD) measurements. Data were collected on a Rigaku Mercury CCD diffractometer equipped with graphitemonochromated Mo Kα radiation (λ = 0.71073 Å) at 293 K. The data sets were corrected for Lorentz and polarization factors as well as for absorption by the Multiscan method.15 The structures were determined by direct methods and refined by full-matrix least-squares fitting on F2 by SHELX-97.16 All non-hydrogen atoms were refined with anisotropic thermal parameters. The hydrogen atoms were located at calculated positions and refined with isotropic thermal parameters. The final refined structural parameters were checked with PLATON.17 Crystallographic data and structural refinements are summarized in Table 1. The final refined atomic positions and structural parameters are listed in Tables S1−12 of the Supporting Information. Magnetic Measurements. Magnetic measurements were performed using a commercial Quantum Design Physical Property Measurement System (PPMS). Powdered samples of Sm2Cu(SO4)2(OH)4 (14.830 mg), Eu2Cu(SO4)2(OH)4 (8.760 mg), and Dy2Cu(SO4)2(OH)4 (10.280 mg) were placed separately in a gel capsule sample holder that was suspended in a plastic drinking straw. The dc magnetic susceptibility was measured at 0.1 T from 300 to 2 K (temperature scan of 5 K/min), and magnetization was measured at 2 K in an applied field from −8 to 8 T (field scan of 0.1 T/step). Low-

EXPERIMENTAL SECTION

Preparation of Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, Tb, or Dy). Single crystals of Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, Tb, or Dy) were synthesized by a conventional hydrothermal method. (1) For Sm2Cu(SO4)2(OH)4, a mixture of 1.5 mmol of CuSO4·7H2O (99.5%, 0.3745 g), 0.6 mmol of Sm2O3 (99.9%, 0.2087 g), 0.3 mmol of K2TeO3 (99.5%, 0.0761 g), 0.5 mmol of H3BO3 (99.5%, 0.0309 g), and 10 mL of deionized water was sealed in an autoclave equipped with a Teflon liner (28 mL). (2) For Eu2Cu(SO4)2(OH)4, a mixture of 1.5 mmol of CuSO4·7H2O (99.5%, 0.3745 g), 0.5 mmol of Eu2O3 (99.9%, 0.1770 g), 0.3 mmol of K2TeO3 (99.5%, 0.0761 g), 0.5 mmol of H3BO3 (99.5%, 0.0309 g), and 10 mL of deionized water was sealed in an autoclave equipped with a Teflon liner (28 mL). (3) For Tb2Cu(SO4)2(OH)4, a mixture of 1.5 mmol of CuSO4·7H2O (99.5%, 0.3745 g), 1 mmol of Tb4O7 (99.9%, 0.7477 g), 0.3 mmol of K2TeO3 (99.5%, 0.0761 g), 0.5 mmol of H3BO3 (99.5%, 0.0309 g), and 10 mL of deionized water was sealed in an autoclave equipped with a Teflon liner (28 mL). (4) For Dy2Cu(SO4)2(OH)4, a mixture of 2 mmol of CuSO4·7H2O (99.5%, 0.5008 g), 1 mmol of Dy2O3 (99.9%, 0.373 g), 0.3 mmol of K2TeO3 (99.5%, 0.0761 g), 1 mmol of H3BO3 (99.5%, 0.0618), and 10 mL of deionized water was sealed in autoclave equipped with a Teflon liner (28 mL). The autoclaves described above were put into a furnace, heated at 210 °C for 4 days under autogenous pressure, and then cooled to room temperature at a rate of ∼2 °C/h for 4 days. The blue bulk crystals of Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, Tb, or Dy) were obtained and further dried at 60 °C for 2 h. The powdered samples were prepared by crushing single crystals of Ln2Cu(SO4)2(OH)4, and their purities were confirmed by powder Xray diffraction studies (Figure S1 of the Supporting Information). In fact, the crystals of Tb2Cu(SO4)2(OH)4 were found to contain powdered CuO impurities that were hard to clean up, and thus, we B

DOI: 10.1021/acs.cgd.5b00057 Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

Figure 2. Structure of Sm2Cu(SO4)2(OH)4 for (a) 3D networks and (b) 2D layers constructed by SmO9 polyhedra and CuO4 squares.

Figure 3. Spin−lattices built by (a) Sm3+ ions, (b) Cu2+ ions, and (c) a combination of Sm3+ and Cu2+ ions. temperature magnetic susceptibilities were also measured with fieldcooling (FC) and zero-field-cooling (ZFC) regimes under 50 Oe. The ac magnetic susceptibilities were measured at an amplitude of 3 Oe with frequencies from 100 to 5000 Hz.

from 86.56(1)° to 180°. All of the CuO4 squares connect to six Sm atoms through a pair of edge-sharing oxygen atoms [O(1)···O(2)] and four corner-sharing oxygen atoms [2O(1) and 2O(2)]. S atoms are coordinated by four oxygen atoms, forming SO42− tetrahedra with S−O bond distances ranging from 1.426(4) to 1.504(3) Å [average of 1.472(6) Å] and O− S−O bond angles ranging from 102.58(2)° to 113.8(2)° [mean of 109.3(9)°]. SO42− tetrahedra link to four Sm atoms through corner-sharing [O(3)−O(5)] or edge-sharing [O(3)···O(5)] oxygen atoms, while O(6) atoms form a dangling bond in SO42− tetrahedra. According to the bond valence sum (BVS) calculations, the values of Sm, Cu, and S atoms are 2.997, 1.867, and 6.052, respectively, proving that these three atoms are consistent with their ideal values. In addition, O(1) and O(2) atoms in this compound are calculated to 0.944 and 0.928, respectively, confirming both O(1) and O(2) atoms should be OH− groups for charge balancing the formula. As shown in Figure 2a, the 3D structural framework of Sm2Cu(SO4)2(OH)4 is composed of two-dimensional (2D) layers and SO42− tetrahedra, in which the 2D layers in the bc plane are composed of SmO9 polyhedra and CuO4 square planes, while the layers are separated by SO42− tetrahedra. As shown in Figure 2b, SmO9 polyhedra connect to each other forming six-column tunnels in the layers, in which CuO4 square planes are located inside the tunnels. To check the linkage of polyhedra in the layers, it is noted that SmO9 polyhedra connect to each other along the b-axis through face-sharing oxygen atoms [O(1)···O(2)···O(3)] with the shortest neighboring Sm−Sm distance being 3.7(9) Å, while SmO9

■

RESULTS AND DISCUSSION Structural Description. Single-crystal X-ray studies of Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, Tb, or Dy) reveal that all the compounds are isostructural and crystallize in the monoclinic system in space group P21/c. Thus, we take Sm2Cu(SO4)2(OH)4 as a representative to describe their structures in detail. For Sm2Cu(SO4)2(OH)4, one Sm atom, one Cu atom, and one S atom are in an asymmetric unit, which are located at Wyckoff positions 4e, 2b, and 4e, respectively. As shown in Figure 1, the Sm atom is located in a 9-oxygencoordinated environment forming a SmO9 polyhedron with Sm−O bond lengths in the range of 2.385(3)−2.544(3) Å and O−Sm−O bond angles in the range of 55.08(1)−148.28(1)°. Each SmO9 polyhedron is surrounded by three Sm atoms, three Cu atoms, and four S atoms, in which Sm connects to S atoms by corner-sharing oxygen atoms [O(3)−O(5)] or edge-sharing oxygen atoms [O(3)···O(5)], while Sm connects to Cu atoms by two corner-sharing oxygen atoms [O(1) and O(2)] or one pair of edge-sharing oxygen atoms [O(1)···O(2)]. Sm atoms connect to each other by one pair of edge-sharing oxygen atoms [O(5)···O(5)] or two pairs of face-sharing oxygen atoms [O(1)···O(2)···O(3)]. The Cu coordination corresponds to a CuO4 square plane with Cu−O bond lengths ranging from 1.958(3) to 1.964(3) Å and O−Cu−O bond angles ranging C

DOI: 10.1021/acs.cgd.5b00057 Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

Figure 4. Temperature dependence of magnetic susceptibility and the corresponding reciprocal for (a) Sm2Cu(SO4)2(OH)4, (b) Eu2Cu(SO4)2(OH)4, and (c) Dy2Cu(SO4)2(OH)4.

Figure 5. χT−T plot for (a) Sm2Cu(SO4)2(OH)4, (b) Eu2Cu(SO4)2(OH)4, and (c) Dy2Cu(SO4)2(OH)4. The inset shows low-temperature susceptibilities obtained with zero-field-cooling (ZFC) and field-cooling (FC) regimes.

Sm2Cu(TeO3)2(SO4)218 and Na3SmMn3O3(AsO4)3.19 For Eu2Cu(SO4)2(OH)4 (Figure 4b), a peak of susceptibility is observed at ∼12.8 K, showing the onset of antiferromagnetic ordering. Typical Curie−Weiss behavior is observed between 150 and 300 K, giving a Curie constant C of 4.8(7) emu mol−1 K and a Weiss temperature θ of −186.2(1) K. The effective magnetic moment can be calculated to be 6.2(4) μB, which is much larger than the theoretical value of 1.73 μB for one Cu2+ (S = 1/2; g = 2) and two Eu3+ ions (S = 0; gJ = 1). This may also be due to the fact that the ground state (7F0) of Eu3+ is close to the first excited state (7F1) and the second excited state (7F2), leading to partial magnetic ions sitting at the excited state. It is well-known that the magnetic moment of Eu3+ is experimentally observed to be near 3.4 μB/mol of Eu in general.20 However, the ground state of Eu3+ at low temperatures is diamagnetic (7F0), and the magnetic interactions in Eu2Cu(SO4)2(OH)4 may arise from Cu2+−Cu2+ antiferromagnetic exchange coupling. It is noted that the coupling distance between Cu2+ ions is quite large and an antiferromagnetic ordering at ∼12.8 K may indicate a strong 3d−4f interaction in the system. A similar magnetic behavior has also been observed in Eu2Cu(TeO3)2(SO4)2.18 For Dy2Cu(SO4)2(OH)4 (Figure 4c), a sudden upturn of susceptibility appears at ∼13.5 K, indicating the onset of ferromagnetic ordering. A typical Curie−Weiss behavior is observed between 60 and 300 K, giving a Curie constant C of 28.3(1) emu mol−1 K and a Weiss temperature θ of 6.3(5) K. The effective magnetic moment can be calculated to be 15.0(5) μB, which is close to the theoretical value of 15.15 μB for one Cu2+ (S = 1/2; g = 2) and two Dy3+ ions (S = 15/2; gJ = 4/3).

polyhedra connect to each other along the c-axis through edgesharing oxygen atoms [O(5)···O(5)] with a Sm−Sm distance of 4.1(9) Å. It must also be noted that CuO4 square planes are located inside the tunnels built by SmO9 polyhedra, resulting in many irregular triangles with μ3-O(1)H and μ3-O(2)H, in which the Sm−Cu distances are 3.4(3), 3.9(5), and 4.0(3) Å. Removing nonmagnetic OH− and SO42− groups from the structure of Sm2Cu(SO4)2(OH)4, we note that the topological structure of Sm3+ ions shows a distorted honeycomb lattice (Figure 3a), while Cu2+ ions are arranged in a triangle lattice (Figure 3b). The spin−lattice built by magnetic Sm3+ and Cu2+ ions is shown in Figure 3c. Magnetic Properties. Figure 4 shows the temperature dependences of magnetic susceptibility (χ) and the corresponding reciprocal (χ−1) for Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, or Dy). For Sm2Cu(SO4)2(OH)4 (Figure 4a), the magnetic susceptibility increases with a decrease in temperature, while a sudden upturn is observed at ∼5.4 K, indicating the onset of ferromagnetic ordering. Typical Curie−Weiss behavior is observed between 220 and 300 K, giving a Curie constant C of 1.5(2) emu mol−1 K and a Weiss temperature θ of −219.0(2) K. The effective magnetic moment can be calculated to be 3.4(9) μB based on the equation of μeff2 = 8C, which has a large derivation from the theoretical value of 2.11 μB for one Cu2+ (S = 1/2; g = 2) and two Sm3+ ions (S = 5/2; gJ = 2/7). This may be due to the fact that the ground state (6H5/2) of Sm3+ is quite close to the first excited state (6H7/2), leading to partial magnetic ions sitting at the excited state, which always makes the experimental value inconsistent with the theoretical value calculated from the pure ground state. Similar phenomena can also be found in many SmO-based compounds such as D

DOI: 10.1021/acs.cgd.5b00057 Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

Figure 6. Curve of magnetization (M) vs applied field (H) at 2 K for (a) Sm2Cu(SO4)2(OH)4, (b) Eu2Cu(SO4)2(OH)4, and (c) Dy2Cu(SO4)2(OH)4. The inset shows the hysteresis loop in the range of −8 to 8 T.

Table 2. Magnetic Data Observed for Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, or Dy) ion Sm3+ Eu3+ Dy3+ a

S

C, emu mol−1 K

μeff, μB

Θ, K

TC, K

magnetic ground statea

/2 0 15 /2

1.5(2) 4.8(7) 28.3(1)

3.4(9) 6.2(4) 15.0(5)

−219.0(2) −186.2(1) 6.3(5)

3.4 12.8 5

FIM AFM FM

gJ 2

/7 1 4 /3

5

Abbreviations: FIM, ferrimagnetic; AFM, antiferromagnetic; FM, ferromagnetic.

Figure 5 shows the χT−T plot for Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, or Dy). For Sm2Cu(SO4)2(OH)4 (Figure 6a), the χT− T plot decreases gradually and reaches its minimum at ∼8 K with a decrease in temperature, while a rapid upturn appears at low temperatures, indicating the existence of ferromagnetic correlation. A clear history is seen below 3.4 K between zerofield-cooling (ZFC) and field-cooling (FC) regimes, confirming the characteristic irreversibility of such a ferromagnetic component (see the inset of Figure 5a). Considering the negative Weiss temperature and ferromagnetic component, the magnetic ground state of Sm2Cu(SO4)2(OH)4 is suggested to be of a ferrimagnetic type. For Eu2Cu(SO4)2(OH)4 (Figure 5b), the χT−T plot decreases gradually with a decrease in temperature, and no peaks can be observed, supporting a collinear antiferromagnetic ground state. For Dy 2 Cu(SO4)2(OH)4 (Figure 5c), the χT−T plot increases gradually with a decrease in temperature, while a rapid increase with a maximum is observed at ∼5 K, confirming the appearance of ferromagnetic ordering. Figure 6 shows the isothermal magnetization as a function of applied field (M−H) at 2 K for Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, or Dy). For Sm2Cu(SO4)2(OH)4 (Figure 6a), the magnetization increases rapidly at the low-field range and then increases gradually with an increasing field up to 8 T. It is noted that an anomaly is observed at ∼4 T, indicating a filedinduced magnetic transition. A clear hysteresis is observed at H ∼ 4 T with increasing and decreasing field regimes (the inset of Figure 6a), supporting the appearance of field-induced magnetic transition. For Eu2Cu(SO4)2(OH)4 (Figure 6b), the magnetization increases linearly with an increasing field and does not saturate at 8 T. This finding is in good agreement with a collinear antiferromagnetic ground state. For Dy2Cu(SO4)2(OH)4 (Figure 6c), the magnetization rapidly increases and saturates at low field. Furthermore, clear hysteresis and remanent magnetization near H = 0 are observed (the inset of Figure 6c), supporting the ferromagnetic ground state. To further identify the nature of magnetic behaviors of Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, or Dy), the ac magnetic susceptibilities were measured with different frequencies

(Figure S2 of the Supporting Information). We note that the peaks of susceptibilities do not shift to high temperatures with an increase in frequency, showing no frequency-dependent behaviors in the systems, which give concrete evidence ruling out the existence of single-molecule magnet (SMM) behavior or spin-glass behavior. It is well-known that magnetic behaviors of solid materials are related strongly to their structures. For pure 4f lanthanidebased compounds, similar magnetic behaviors are usually observed because of their similar structural features.21−23 However, we note that Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, or Dy) compounds exhibit quite different magnetic behaviors, although they have a similar structural feature. This may indicate that lanthanide Ln3+ ions play a remarkable role in magnetic behaviors of such 3d−4f heterometallic hydroxysulfates. Table 2 shows the magnetic behaviors of Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, Tb, or Dy). The change in Weiss temperature θ from negative to positive is observed from Sm3+ to Dy3+ in the systems, showing that the nearest magnetic interactions vary from antiferromagnetic to ferromagnetic between magnetic ions with the decreasing radii of Ln3+ ions. This character is consistent with that observed in Ln2Cu(TeO 3 ) 2(SO 4) 2 ,18 [Ln 2Cu 4 (fsaaep)4 (NO3 ) 6]·0.5(CH3 OH· H2O),24 and {Ln2[Cu(opba)]3}·S,25 in which the coupling exchanges between Ln3+ and Cu2+ ions are antiferromagnetic for light rare earths and ferromagnetic for heavy rare earths.26 Infrared Spectroscopy. Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, or Dy) compounds are characterized by the FT-IR spectrum (Figure S3 of the Supporting Information). It is noted that all the infrared spectra are quite similar, supporting polyhedra of these compounds with similar oxygen coordination environments. For hydroxyl groups, two sharp peaks at 3573 and 3435 cm−1 are due to the stretching modes of OH groups and another band at around 1635 and 870 cm−1 can be attributed to their bending modes. For sulfate groups, all the fundamental modes (ν1−ν4) could be observed clearly in the spectrum. The ν1 (970 cm−1) and ν2 (454 cm−1) modes indicate the lowering of site symmetry from the Td group of sulfate groups. In particular, the ν3 mode is split into three E

DOI: 10.1021/acs.cgd.5b00057 Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

separate peaks between 1235 and 1028 cm−1, and those between 730 and 600 cm−1 can be attributed to the ν4 mode of the sulfate groups.

Johnson, K.; Sovesky, R.; Stroudt, C.; Renn, R. A. Inorg. Chem. 2011, 50, 836. (8) West, J. P.; Queen, W. L.; Hwu, S.-J.; Michaux, K. E. Angew. Chem., Int. Ed. 2011, 50, 3780. (9) Hardy, V.; Martin, C.; Martinet, G.; Andre, G. Phys. Rev. B 2006, 74, 064413. (10) Smith, M. D.; zur Loye, H.-C. Chem. Mater. 2000, 12, 2404. (11) Wang, X. Q.; Liu, L. M.; Jacobson, A. J. J. Solid State Chem. 1999, 147, 641. (12) Wang, X. Q.; Liu, L. M.; Ross, K.; Jacobson, A. J. Solid State Sci. 1998, 2, 109. (13) Casari, B. M.; Langer, V. Eur. J. Inorg. Chem. 2007, 22, 3514. (14) Tang, Y. Y.; Guo, W. B.; Zhang, S. Y.; Yang, M.; He, Z. Z. Cryst. Growth Des. 2014, 14, 5206. (15) CrystalClear, version 1.3.5; Rigaku Corp.: The Woodlands, TX, 1999. (16) Sheldrick, G. M. Crystallographic Software Package, SHELXTL, version 5.1; Bruker-AXS: Madison, WI, 1998. (17) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7. (18) Lin, J.; Chai, P.; Diefenbach, K.; Shatruk, M.; Albrecht-Schmitt, T. E. Chem. Mater. 2014, 26, 2187. (19) West, J. P.; Hwu, S.-J.; Queen, W. L. Inorg. Chem. 2009, 48, 8439. (20) Kittel, C. Introduction of Solid State Physics, 6th ed.; Wiley: New York, 1986. (21) Thompson, C. M.; Tan, X. Y.; Kovnir, K.; Garlea, V. O.; Gippius, A. A.; Yaroslavtsev, A. A.; Menushenkov, A. P.; Chernikov, R. V.; Buttgen, N.; Kratschmer, W.; Zubavichus, Y. V.; Shatruk, M. Chem. Mater. 2014, 26, 3825. (22) Munoz, A.; Martinez-Lope, M. J.; Alonso, J. A.; Fernandez-Diaz, M. T. Eur. J. Inorg. Chem. 2012, 35, 5825. (23) Martinez-Coronado, R.; Retuerto, M.; Fernandez, M. T.; Alonso, J. A. Dalton Trans. 2012, 41, 8575. (24) Andruh, M.; Ramade, I.; Codjovi, E.; Guillou, O.; Kahn, O.; Trombe, J. C. J. Am. Chem. Soc. 1993, 115, 1822. (25) Kahn, M. L.; Mathoniere, C.; Kahn, O. Inorg. Chem. 1999, 38, 3692. (26) Kahn, O.; Guillou, O. Research Frontiers in Magnetochemistry; O’Connor, C., Ed.; World Scientific: Singapore, 1993.

■

CONCLUSIONS We have successfully obtained a series of novel 3d−4f hydroxysulfates Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, Tb, or Dy) by means of a conventional hydrothermal method. All of the compounds are isostructural and crystallize in the monoclinic system in space group P21/c. A layered structure is composed of LnO9 polyhedra and CuO4 planar squares, and the layers are further separated by SO42− tetrahedra. The topological structure of Ln3+ ions corresponds to a distorted honeycomb lattice, while Cu2+ ions are located at the hole of the honeycomb framework forming a triangle lattice. Magnetic measurements confirm that Ln2Cu(SO4)2(OH)4 compounds exhibit different magnetic properties, in which Sm2Cu(SO4)2(OH)4 shows a ferrimagnetic ground state and Eu2Cu(SO4)2(OH)4 displays antiferromagnetic ordering at ∼12.8 K, while Dy2Cu(SO4)2(OH)4 shows ferromagnetic ordering at ∼5 K. We believe that this study of Ln2Cu(SO4)2(OH)4 is a typical example for investigating different 3d−4f coupling exchanges between magnetic ions, which strongly affect their magnetic behaviors.

■

ASSOCIATED CONTENT

S Supporting Information *

Final refined atomic positions and structural parameters, ac magnetic susceptibilities, infrared spectra, and simulated and experimental powder X-ray patterns for Ln2Cu(SO4)2(OH)4 (Ln = Sm, Eu, Tb, or Dy). The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.cgd.5b00057.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected] or [email protected]. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was financially supported by the National Basic Research Program of China (2012CB921701) and the National Natural Science Foundation of China (21403234).

■

REFERENCES

(1) Subban, C. V.; Ati, M.; Rousse, G.; Abakumov, A. M.; Van Tendeloo, G.; Janot, R.; Tarascon, J.-M. J. Am. Chem. Soc. 2013, 135, 3653. (2) Rujiwatra, A.; Kepert, C. J.; Claridge, J. B.; Rosseinsky, M. J.; Kumagai, H.; Kurmoo, M. J. Am. Chem. Soc. 2001, 123, 10584. (3) Ben Salah, M.; Vilminot, S.; Andre, G.; Bouree-Vigneron, F.; Richard-Plouet, M.; Mhiri, T.; Kurmoo, M. Chem. Mater. 2005, 17, 2612. (4) Vilminot, S.; Andre, G.; Bouree-Vigneron, F.; Richard-Plouet, M.; Kurmoo, M. Inorg. Chem. 2007, 46, 10079. (5) Ben Salah, M.; Vilminot, S.; Andre, G.; Richard-Plouet, M.; Takagi, S.; Kurmoo, M. J. Am. Chem. Soc. 2006, 128, 7972. (6) Zhang, X.-M.; Li, C.-R.; Zhang, X.-H.; Zhang, W.-X.; Chen, X.-M. Chem. Mater. 2008, 20, 2298. (7) Zehnder, R. A.; Wilson, C. S.; Christy, H. T.; Harris, K. S.; Chauhan, V.; Schutz, V.; Sullivan, M.; Zeller, M.; Fronczek, F. R.; Myers, J. A.; Dammann, K.; Duck, J.; Smith, P. M.; Okuma, A.; F

DOI: 10.1021/acs.cgd.5b00057 Cryst. Growth Des. XXXX, XXX, XXX−XXX