Communication pubs.acs.org/crystal
Large Heterometallic Dy12Na6 Cage-like Cluster Supported by in Situ Generated Ligand Guo-Ming Wang,* Jin-Hua Li, Song-De Han, Jie Pan, Li Wei, Zong-Hua Wang, and Zhen-Zhen Bao College of Chemistry and Chemical Engineering, Collaborative Innovation Center for Marine Biomass Fiber Materials and Textiles, Qingdao University, Shandong 266071, P. R. China S Supporting Information *
ABSTRACT: A novel heterometallic cluster, Dy12Na6, has been prepared and characterized. It represents an unprecedented high-nuclearity alkali-metal-Ln cluster with a cage-like shape. In situ generated ligands participated in the formation of the heterometallic cluster. Magnetic measurements suggest that Dy12Na6 shows slow magnetic relaxation at low temperature.
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cluster for generating innovative AM-Ln clusters with fascinating properties. Representative cases for the reported AM-Ln clusters are K20Sm4,15 Na6Eu9,16 NaLn12,17 NaCe10.18 However, compared with the large nuclearity and fascinating structures in TM-Ln (e.g., La76Ni60,10 Cu36Ln244) and TM-TM′ (e.g., Mn36Ni4,5 Cu17Mn286) clusters, the development of AMLn cluster is still in its infancy. Herein, we report a heterometallic cluster [Dy12Na6(μ3OH)4(OAc)12(L)12](NO3)2·(CH3CN)5·(CH3OH) (1, OAc− = acetate, L2− = 6,6′-(oxybis(methylene)) bis(2-methoxyphenolate)),19 with triangular Dy3 units as the building block and inorganic Na+ ions as the linker. 1 was synthesized from the solvothermal reaction of Dy(NO3)2·6H2O, NaOH, fumaric acid, and o-vanillin in a methanol−acetonitrile mixed solvent at 120 °C for 5 days.20 During this course, the o-vanillin underwent an in situ reaction, and a new ligand 6,6′(oxybis(methylene)) bis(2-methoxyphenol) (H2L) has been produced. Furthermore, the in situ generated acetate from the hydrolysis of acetonitrile solvent acted as a coligand to promote the formation of the final product. 1 crystallizes in the space group of P63 (No. 173, trigonal system). All in situ generated H2L ligands feature the dianionic form L2− and take the η1:η1:η1:η1:η1:μ3-bridging mode to connect one Na+ and two Dy3+ ions (Figure 1, Figure S1). All acetates display the η1:η2:μ3 (or syn,syn,anti)-bridging mode to bridge one Na+ and two Dy3+ ions (Figure 1, Figure S1). All metal ions are oxygen coordinated. The cationic core of 1 is composed of 12 Dy3+ ions, six Na+ ions, 12 L2− ligands, four μ3-
igh-nuclearity metal complexes have captured significant attention due to their appealing architectures and potential applications in numerous areas.1−3 Compared with homometallic clusters, the heterometallic species have received strong interest because the assembly of different metal ions in a discrete skeleton may generate novel materials with interesting properties.4−6 The combination of transition metal (TM) and lanthanide (Ln) ions, for example, produces a rapidly growing family of TM-Ln clusters as single molecule magnet (SMM), molecular magnetic coolers and catalyst, etc.7−9 Several stages have been experienced in the development of heterometallic polynuclear complexes: from oligonuclear to giant polynuclearin nuclearity; from simple geometry to complicated wheel (or ring) and cage in shape; from regular synthesis to hydro(solvo)thermal synthesis and microwave synthesis in synthetic methods, etc.10−12 However, the construction of such targeted complexes with particular nuclearity and shape is still a great challenge for researchers. Choosing polydentate ligand with suitable coordination sites plays a paramount role in the creation of heterometallic clusters. For example, the predesigned Schiff base ligands containing N and O sites have been well utilized to fabricate the TM-Ln clusters.13,14 Driven by the coordination preferences of TM and Ln ions together with the potential fascinating magnetism and luminescence related to certain Ln ions, the TM-Ln clusters have witnessed flourishing development in terms of shape and nuclearity.10,11 In contrast, little focus has been given to alkali-metal (AM)-Ln clusters owing to the flexible coordination geometry of the AM ion together with the coordinative competition in the process of assembly. Inspired by the quest of a new system for a heterometallic cluster, researchers attempted to introduce AM ions into a lanthanide © XXXX American Chemical Society
Received: February 13, 2016 Revised: March 4, 2016
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DOI: 10.1021/acs.cgd.6b00239 Cryst. Growth Des. XXXX, XXX, XXX−XXX
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Communication
confirmed by the IR typical peaks (1366, 1319, and 850 cm−1) for nitrate (Figure S12). Analyzing the solvothermal conditions and the product offers a tentative mechanism for the in situ generation of L2− and acetate. This is mainly attributable to the strong basic conditions in the system. It is well-known that cyanide has a tendency to hydrolyze to form carboxylate under basic conditions. The strong basic conditions and the sealed solution reactions at elevated temperature and pressure may promote the hydrolysis of acetonitrile and the creation of acetate. The hydrolysis of the nitrile group to obtain carboxylate has been well used in organic synthesis.21 The in situ generated acetate in 1 can also be testified by the IR typical peaks (1628, 1596, and 1552 cm−1) for acetate (Figure S12). The production of L2− ligands could be comprehended as a two-step reaction (Scheme 1). The first step is the Cannizzaro reaction of o-vanillin to Scheme 1. Possible Formation Routes of the in Situ Generated Ligands from o-Vanillin
Figure 1. Coordination modes of metal ions and ligands in 1 (balland-stick view). H atoms omitted for clarity. C: turquiose, O: red, Na: bright green, Dy: pink. Symmetry code: A: 1 − y, x − y, z; B: 1 − x + y, 1 − x, z.
OH− anions and 12 acetate groups. All the octa-coordinate Dy3+ ions display a distorted square antiprism geometry coordinated by one O atom of μ3-OH− group, two O atoms belonging to two acetate, and five O atoms from two L2− ligands (Figure 1, Figures S2 and S3). The Dy···O bond lengths range from 2.251(6)−2.635(6) Å, which is analogous to those reported Dy-based complexes with O atoms as coordination sites. The Na+ centers possess a highly distorted octahedral geometry finished by the coordination of two O atoms from two acetate and four O atoms belonging to two L2− groups with Na···O distances in the scope of 2.359(6)−2.427(7) Å (Figure 1, Figures S4 and S5). One μ3-OH− anion, together with three acetate and three L2− ligands, bridge three Dy3+ ions to form the [Dy3(μ3OH)(OAc)3(L)3]− building units (Dy3, for short) (Figure 2a,
generate 2-(hydroxymethyl)-6-methoxyphenol (H2L′) under basic conditions. A similar in situ reaction has been corroborated by Tong and co-workers.22 The second is the condensation reaction of H2L′ to form L2− ligands. Although the in situ reaction of carbonyl such as Cannizzaro reaction, oxidation reaction, and aldol reaction has been well utilized by researchers to fabricate homo- and heterometallic polynuclear complexes,23 the two-step in situ reaction mentioned above has not been reported so far. Compared with the common in situ ligand reaction between heteromolecules (an organic ligand and a small/solvent molecule),24 this study offers a limited case for homomolecular reaction (one organic ligand attacked another).22,25 All of the ligands participated in the formation of 1 are generated in situ, which is also distinct from the reported clusters. Hitherto, there are few reported AM-Ln clusters with nuclearity larger than 10.15−18 The nuclearity of 1 is larger than most of the reported AM-Ln clusters. It is notable that 1 displays a cage-like shape. Compared with TM ions, the construction of cage-like structures containing Ln ions may be a huge challenge, owing to the flexible coordination behavior of Ln ions. This study provides a rare Ln-MA cluster with a cage-like shape.17 The variable-temperature magnetic susceptibility for 1 was studied under a 0.1 T applied field (Figure 3). The phase purity of 1 was testified by powder X-ray diffraction (PXRD) plots (Figure S11). At 290 K, the observed χMT product of 165.89 cm3 mol−1 K for 1 is slightly smaller than the theoretical values for the unit of 12 noninteracting Dy3+ (170.00 cm3 K mol−1, 6 H15/2, g = 4/3). Upon cooling, χMT decreases smoothly to 152.32 cm3 mol−1 K at 24 K, and then it increases obviously to a maximum value of 163.23 cm3 mol−1 K at 3 K. Below this temperature it falls again to 159.46 cm3 mol−1 K at 2 K. The initial drop of χMT on cooling may be due to the thermal depopulation of the Stark levels of Dy3+ and/or possible weak intratrimer antiferromagnetic interactions between the Dy3+
Figure 2. Dy3 building unit connected by three Na+ ions (a) and the molecular structure of Dy12Na6 (b) for 1 (ball-and-stick view). All free units and H atoms omitted for clarity.
Figure S6a). Notably, there are two categories of Dy3 building units in the structure of 1. The first one contains three crystallographically independent Dy3+ ions (Dy(1)3+, Dy(1)3+, and Dy(3)3+), while the second one contains three symmetryrelated Dy(4)3+ ions (Figure 1). The core of 1 can be considered as an octadecanuclear heterometallic cationic cluster Dy12Na6 built from four Dy3 trimers, three in the first kind and one in the second, bridged by six Na+ ions (three Na(1)+ and three Na(2)+ ions) (Figure 2b, Figure S6b). The charge is balanced by free NO3− ions. The existence of NO3− can also be B
DOI: 10.1021/acs.cgd.6b00239 Cryst. Growth Des. XXXX, XXX, XXX−XXX
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enlarges the existing family of AM-Ln clusters, but also offers a scarce case of cage shape and large nuclearity. Further investigations on this work, including the construction of other intricate heterometallic clusters with fascinating properties, are underway.
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.cgd.6b00239. Experimental section, supplementary structural figures, additional properties characterizations, selected bond lengths and angles (PDF) Accession Codes
CCDC 1436508 contains 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.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS We acknowledge the grants from the NSFC projects (No. 21571111) of China and Taishan Scholar Program.
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Figure 3. χMT vs T (top) and χM″ vs T (bottom) curves for 1.
REFERENCES
(1) Argent, S. P.; Greenaway, A.; Gimenez-Lopez, M. d. C.; Lewis, W.; Nowell, H.; Khlobystov, A. N.; Blake, A. J.; Champness, N. R.; Schröder, M. J. Am. Chem. Soc. 2012, 134, 55. (2) Kang, S.; Zheng, H.; Liu, T.; Hamachi, K.; Kanegawa, S.; Sugimoto, K.; Shiota, Y.; Hayami, S.; Mito, M.; Nakamura, T.; Nakano, M.; Baker, M. L.; Nojiri, H.; Yoshizawa, K.; Duan, C.; Sato, O. Nat. Commun. 2015, 6, 5955. (3) Peng, J.-B.; Kong, X.-J.; Zhang, Q.-C.; Orendác,̌ M.; Prokleška, J.; Ren, Y.-P.; Long, L.-S.; Zheng, Z.; Zheng, L.-S. J. Am. Chem. Soc. 2014, 136, 17938. (4) Leng, J.-D.; Liu, J.-L.; Tong, M.-L. Chem. Commun. 2012, 48, 5286. (5) Charalambous, M.; Moushi, E. E.; Papatriantafyllopoulou, C.; Wernsdorfer, W.; Nastopoulos, V.; Christou, G.; Tasiopoulos, A. J. Chem. Commun. 2012, 48, 5410. (6) Wang, W.-G.; Zhou, A.-J.; Zhang, W.-X.; Tong, M.-L.; Chen, X.M.; Nakano, M.; Beedle, C. C.; Hendrickson, D. N. J. Am. Chem. Soc. 2007, 129, 1014. (7) Rosado Piquer, L.; Sanudo, E. C. Dalton Trans. 2015, 44, 8771. (8) Peng, J.-B.; Zhang, Q.-C.; Kong, X.-J.; Ren, Y.-P.; Long, L.-S.; Huang, R.-B.; Zheng, L.-S.; Zheng, Z. Angew. Chem., Int. Ed. 2011, 50, 10649. (9) Evangelisti, F.; Moré, R.; Hodel, F.; Luber, S.; Patzke, G. R. J. Am. Chem. Soc. 2015, 137, 11076. (10) Kong, X.-J.; Long, L.-S.; Huang, R.-B.; Zheng, L.-S.; Harris, T. D.; Zheng, Z. Chem. Commun. 2009, 4354. (11) Zhang, Z.-M.; Pan, L.-Y.; Lin, W.-Q.; Leng, J.-D.; Guo, F.-S.; Chen, Y.-C.; Liu, J.-L.; Tong, M.-L. Chem. Commun. 2013, 49, 8081. (12) Zhang, S.-H.; Song, Y.; Liang, H.; Zeng, M.-H. CrystEngComm 2009, 11, 865.
ions. The obvious increase of χMT below 24 K indicates the presence of ferromagnetic couplings. The variable-temperature molar susceptibility at 2−300 K could be well fitted by the Curie−Weiss law, yielding Curie constant C = 166.39 cm3 mol−1 K and Weiss constant θ = −2.36 K (Figure S8). At 2 K, the variable-field magnetizations increase quickly under low fields ( 2θ(I)); R1 = 0.0522, wR2 = 0.1122 (all data) and GOF = 1.061. CCDC: 1436508. The main framework of 1 is dicationic. Considering the sources of anion in the formation of 1, the negative charge may be balanced by two nitrate anions. However, these units cannot be modeled properly. The “SQUEEZE” method in PLATON was used to treat the highly disordered units (counteranions and solvents molecules) in 1, and the detailed results are in the section “X-ray Crystallography” in the Supporting Information. (20) o-Vanillin (0.076 g, 0.5mmol), fumaric acid (0.093 g, 0.8 mmol), Dy(NO3)3·6H2O (0.228 g, 0.5mmol), NaOH (0.112 g, 2.8mmol), MeOH (5 mL), and MeCN (5 mL) were mixed and encapsulated in a 20 mL Teflon-lined autoclave and heated to 120 °C for five days then slowly cooled to room temperature in half a day. Isostructural Tb12Na6 and Eu12Na6 could also be prepared with the same method; however, after substituting NaOH with LiOH or KOH, no crystalline materials could be obtained. Yield: ca. 20% based on o-vanillin. Elemental analysis (%): Calcd: C, 40.78; H, 3.78; N, 1.47. Exp: C, 40.95; H, 3.54; N, 1.48. IR (KBr pellets, cm−1): 3423(s), 3055(w), 3013(w), 2933(m), 2836(m), 1628(s), 1596(s), 1552(m), 1486(s), 1450(m), 1397(m), 1366(m), 1319(s), 1287(s), 1237(s), 1219(s), 1166(m), 1105(m), 1076(s), 1013(m), 987(w), 957(w), 852(s), 786(m), 738(s), 649(m), 615(m), 597(m), 545(m), 511(m). (21) Zhao, N.; Wang, K.; Li, W.; Bian, Y.; Sun, C.; Chang, Z.; Fan, H. Solid State Sci. 2011, 13, 1948. (22) Liu, J.-L.; Lin, W.-Q.; Chen, Y.-C.; Gómez-Coca, S.; Aravena, D.; Ruiz, E.; Leng, J.-D.; Tong, M.-L. Chem. - Eur. J. 2013, 19, 17567. (23) Gavrilenko, K. S.; Punin, S. V.; Cador, O.; Golhen, S.; Ouahab, L.; Pavlishchuk, V. V. J. Am. Chem. Soc. 2005, 127, 12246. (24) Mautner, F. A.; El Fallah, M. S.; Speed, S.; Vicente, R. Dalton Trans. 2010, 39, 4070. (25) Anwar, M. U.; Lan, Y.; Beltran, L. M. C.; Clérac, R.; Pfirrmann, S.; Anson, C. E.; Powell, A. K. Inorg. Chem. 2009, 48, 5177. (26) Han, S.-D.; Wang, Q.-L.; Xu, J.; Bu, X.-H. Eur. J. Inorg. Chem. 2015, 2015, 5379. (27) Mazarakioti, E. C.; Cunha-Silva, L.; Bekiari, V.; Escuer, A.; Stamatatos, T. C. RSC Adv. 2015, 5, 92534.
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DOI: 10.1021/acs.cgd.6b00239 Cryst. Growth Des. XXXX, XXX, XXX−XXX
