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Two novel FeII-oxalate architectures: Solvent-free synthesis, structures, thermal and magnetic studies
Solid State Sciences 48 (2015) 225e229
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Solid State Sciences journal homepage: www.elsevier.com/locate/ssscie
Two novel FeII-oxalate architectures: Solvent-free synthesis, structures, thermal and magnetic studies Jin-Hua Li a, **, Hui Liu b, Li Wei a, Guo-Ming Wang a, * a
College of Chemical Science and Engineering, Collaborative Innovation Center for Marine Biomass Fiber Materials and Textiles, Teachers College, Qingdao University, Shandong 266071, China b Department of Clinical Laboratory, Women and Children Hospital of Qingdao, Shandong 266034, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 1 July 2015 Received in revised form 6 August 2015 Accepted 20 August 2015 Available online 24 August 2015
Two novel FeII-oxalate framework with the formulas of [NH4][FeIILi3(C2O4)3] (1) and [NH4]2[FeII(C2O4)2]$ H2O (2) have been prepared by an oxalic acid flux approach and structurally characterized by IR, elemental analysis, thermogravimetric analysis, single-crystal and powder X-ray diffraction. Heterometallic compound 1 displays a three-dimensional (3D) framework with a pto topology, while homometallic compound 2 features a pillar-layer architecture with a hms topology. Thermal analysis indicates that the two compounds can be stable up to 300 C and 200 C, respectively. Magnetic investigations suggest that the FeII ions in 1 and 2 exhibit weak magnetic exchange interactions. © 2015 Elsevier Masson SAS. All rights reserved.
Keywords: Iron Oxalate Crystal structure Metal-carboxylate frameworks Topology
1. Introduction Metal carboxylates with open frameworks exhibits diverse structural chemistry and hold great promises in numerous areas such as catalysis, adsorption, separation, optics and drug release [1e8]. Owing to their low toxicity, environmental friendliness, interesting magnetism, and potential application in medicines and batteries, the iron carboxylates with open architectures attract considerable attention of researchers [9e17]. However, the rational design of such materials is still a challenging task for researchers due to the factor that the iron ions feature strong tendency of hydrolysis into stable polymeric iron oxide [18,19], which makes the preparation of targeted frameworks more difficult and usually give rise to precipitation rather than crystallization. Among the strategies to this goal, adopting sound synthetic methods to hinder the hydrolysis of iron ions is the key to create open framework ion carboxylates. A review of the available reference indicates that iron-carboxylates architectures are generally synthesized via solution-based syntheses [9e19]. Although the use
* Corresponding author. ** Corresponding author. E-mail addresses: [email protected] (J.-H. Li), [email protected] (G.-M. Wang). http://dx.doi.org/10.1016/j.solidstatesciences.2015.08.017 1293-2558/© 2015 Elsevier Masson SAS. All rights reserved.
of organic solvents could avoid the hydrolysis of iron ion to some extent, the organic solvents together with soluble salt usually restrict the final yield and generate a great deal of byproducts, which is not economic and environment-friendly [20]. By contrast, the new solvent-free syntheses possess several intrinsic merits over conventional solvent-based approach: low cost, easy handling, reducing pollution, and decreasing system pressure [21e24]. Moreover, novel open-framework structures with unique topologies may be generated by this approach because of the reduction or elimination of solvent-effect on the resulting structure [25e27]. Taking into account the points mentioned above, we attempted to explore the preparation of open framework iron oxalate via nonsolvent syntheses of FeCl3$6H2O, oxalic acid in the presence of urea and LiCl based on the following considerations: (a) oxalic acid with a relatively low melting point of 101.5 C is suitable for solvent-free flux synthesis, which could effectively avoid the hydrolysis of iron ion; (b) the rigid bidentate ligand oxalate can readily form extended frameworks by linking metal ions in various modes; (c) urea not only facilitates the deprotonation of oxalic acid but also decomposes in situ to generate ammonium (NHþ 4 ) as structure-directing agents under given conditions [28]; (d) extended networks containing the lightest elements lithium could be used to fabricate lightweight open framework with fascinating structures and properties [29e32].
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With these points in mind, we successfully isolated two novel Fe-oxalate framework with the formulas of [NH4][FeIILi3(C2O4)3] (1) and [NH4]2[FeII(C2O4)2]$H2O (2). The structures, topological analyses, thermal and magnetic properties of 1 and 2 have been thoroughly investigated. 2. Experimental section 2.1. Materials and methods All chemicals were of analytical grade (AR) and used as received. CHN analyses were performed on a PerkineElmer 240 C analyzer (PerkineElmer, USA). IR spectra were obtained from a MAGNA-560 (Nicolet) FT-IR spectrometer with KBr pellets. Powder X-ray diffraction (PXRD) spectra were collected on a Bruker D8 FOCUS diffractometer with a Cu-target tube and a graphite monochromator. The simulated PXRD spectra were generated from the single-crystal data via the Mercury (Hg) program that are freely available from the internet at http://www.iucr.org. The magnetic measurements were carried out on an MPMS XL-7 SQUID magnetometer. Diamagnetic corrections were estimated via utilizing Pascal constants and experimental corrections for the sample holder were applied. Thermogravimetric analyses (TGA) were conducted on a Rigaku standard TG-DTA analyzer with a heating rate of 10 C min1 from ambient temperature to 700 C under nitrogen gas. 2.2. Synthesis [NH4][FeIILi3(C2O4)3] (1). A mixture of FeCl3$6H2O (0.540 g, 2 mmol), H2C2O4$2H2O (2.520 g, 20 mmol), urea (0.600 g, 10 mmol), LiCl (0.340 g, 8 mmol)was sealed in a Teflon-lined autoclave (20 mL) and heated to 140 C for 72 h then slowly cooled to 30 C in 24 h. Yield: ca. 70% with respect to FeCl3$6H2O. Elemental analysis (%): Calcd. For C6H4NFeLi3O12 (358.76): C 20.09, N 3.90, H 1.12. Found: C 20.20, N 3.98, H 1.45. IR (KBr pellets, cm1): 3277(s), 2954(w), 1662(s), 1630(s), 1480(s), 1416(s), 1347(m), 1320(s), 913(w), 860(w), 811(s), 603(m), 480(s). [NH4]2[FeII(C2O4)2]$H2O (2). A mixture of FeCl3$6H2O (0.270 g, 1 mmol), H2C2O4$2H2O (1.260 g, 10 mmol), urea (0.300 g, 5 mmol), LiCl (0.170 g, 4 mmol) was sealed in a Teflon-lined autoclave (20 mL) and heated to 140 C for 72 h then slowly cooled to 30 C in 24 h. Yield: ca. 20% with respect to FeCl3$6H2O. Elemental analysis (%): Calcd. for C4H10N2FeO9 (285.98): C 16.80, N 9.80, H 3.52. Found: C 16.53, N 10.16, H 3.85. IR (KBr pellets, cm1): 3546(s), 3311(s), 3159(s), 3069(s), 2353(w), 1666(s), 1617(s), 1424(s), 1308(s), 904(w), 861(w), 784(s), 770(s), 612(m), 510(s). 2.3. Determination of crystal structure The single-crystal X-ray diffraction data for compounds 1 and 2 were collected on a Rigaku SCX-mini diffractometer at 293(2) K with Mo-Ka radiation (l ¼ 0.71073 Å) by uscan mode. The program CrystalClear was used for the integration of the diffraction profiles [33]. All structures were solved by direct method using the SHELXS program of the SHELXTL package and refined by full-matrix leastsquares methods with SHELXL (semi-empirical absorption corrections were applied by using the SADABS program) [34]. Heavy metal atoms in each compound were located from the E-maps and other non-hydrogen atoms were located in successive difference Fourier syntheses and refined with anisotropic thermal parameters. The hydrogen atoms of ammonium and the free water were not added and included directly in the molecular formula. Detailed crystallographic data are summarized in Table 1 and the selected bond lengths and angles are given in Tables S3 and S4. Full
Table 1 Crystal data and structure refinement parameters for compounds 1 and 2. 1 Formula Mr (g mol1) Space group Crystal system a (Å) b (Å) c (Å) a( ) b( ) g( ) V (Å3) Z F(000) Dc (g cm3) m (mm1) Rint limiting indices
C6H4NFeLi3O12 358.76 Re3c Trigonal 11.5273(16) 11.5273(16) 15.169(3) 90 90 120 1745.5(5) 6 1068 2.048 1.367 0.1028 13 h 13 13 k 13 18 l 18 Collected reflections 4574 Unique reflections 345 GOF on F2 1.211 R1,wR2[I > 2s(I)]a 0.05600.1246 R1,wR2 [all data]b 0.05940.1271 P P P P a R1 ¼ jjFoj-jFcjj/ jFoj.bwR2 ¼ { [w(F2o- F2c )2]/ w(F2o)2}1/2.
2 C4H10N2FeO9 285.98 P321 Trigonal 10.2055(14) 10.2055(14) 7.3773(15) 90 90 120 665.42(19) 3 438 2.141 1.747 0.0338 13 h 13 13 k 13 9 l 9 7061 1027 1.302 0.06340.1675 0.06420.1679
crystallographic data for 1 and 2 have been deposited with the CCDC number 1405302 for 1 and 1405301 for 2. These data can be freely available from the Cambridge Crystallographic Data Centre at www.ccdc.cam.ac.uk/data_request/cif. 3. Results and discussion 3.1. Syntheses It is notable that the urea plays an important role in the formation of 1 and 2. Firstly, the basic urea promoted the generation of deprotonated oxalic acid. Secondly, the in situ decomposition of urea offers ammonia that could provide more basic conditions, which were helpful for the fabrication of high dimensional frameworks by further deprotonation of oxalic acid. Thirdly, the in situ generated NHþ 4 originated from the protonated ammonia could not only act as a counter cation but also the structure-directing agents to guide the fabrication of anionic open frameworks with special structures and properties. Interestingly, when the amount of reactants for 1 was reduced by a factor of two, compounds 1 and 2 formed together. However, further reducing the amount of reactants by a factor of three or four could not obtain 1 and 2. Attempts to prepare 2 with FeCl3$6H2O, H2C2O4$2H2O and urea in the absence of LiCl were fruitless, and we believe LiCl may play an important and subtle role in the crystallization process of 2. The FeII ions in 1 and 2 may come from the reduction of FeIII by oxalic acid. The reduction of FeIII to FeII ions has been reported in formate system [16,17]. 3.2. Structural description Crystallographic studies revealed that compound 1 crystallizes in a trigonal system with space group Re3c. Its structure consists of the [FeIILi3(C2O4)3]anionic framework, and NHþ 4 ions exist in the 1D channels to balance the negative charges. All FeII and LiI sites are six coordinated. All oxalate ligands are in h2:h2:h2:h2:m4-bridging mode to link one FeII and three LiI ions. The detailed bond valence sum (BVS) indicates that all iron ions are FeII (Table S1). The Fe1
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center displays an octahedral [FeO6] geometry formed by the coordination of six symmetry-related O1 atoms from three symmetry-related oxalate ligands (Fig. 1a). The Li1 center exhibits a distorted octahedral [LiO6] geometry formed by the coordination of four symmetry-related O1and two symmetry-related O2 atoms from three symmetry-related oxalate ligands (Fig. 1a). The FeeO bond distances are 2.191(6) Å, while the LieO bond distances range from 2.475(2) to 2.687(2) Å. Each FeII connects nine adjacent LiI ions via three oxalate ligands, and each LiI links three neighboring FeII and six adjacent LiI ions by three oxalate ligands. The strictly alternative arrangement of FeII and LiI gives rise to the final 3D framework of 1. It is worthy to note that the resultant architecture is distinct from the reported heterometallic FeIIIeLiI oxalate compounds [35,36], in which the Li ions with two types of coordination modes (i.e. octahedron and tetrahedron) participated in the formation of the framework. In addition, owing to the reduction of FeIII by oxalic acid, the bond valance of iron in 1 is þ 2, which is also different from other FeIIIeLi heterometallic oxalate network [35e37]. There has 1D channel in the structure of 1, which is þ partially occluded by NHþ 4 (Fig. 1b). The hydrogen atoms of NH4 form H-bonds with the oxygen atoms of the anionic framework. Thus, it is reasonable for us to contend that the NHþ 4 acts as a template or structure-directing agent in the formation of 1. To better understand the framework of 1, it is necessary to simplify its structure from the topological viewpoint. The Fe/Li centers coordinated to three oxalates could be considered as 3-connected nodes, while the m4-bridging oxalate could be viewed as 4connected nodes. Therefore, the whole 3D structure can be ratio€fli) nalized as a binodal (3,4)-connected pto net with point (Schla symbol (83)4(86)3 calculated with TOPOS (Fig. 1c) [38]. Interestingly, distinct from the reported pto net composed of 4-connected square-planar metal-carboxylate units and 3-connected triangular carboxylate units [39e41], the pto net of 1 was comprised of 3connected metal units and 4-connected square rigid tetradentate oxalate units. Compound 2 crystallizes in a trigonal system with space group P321. The anionic framework of 2 could be comprehended as a pillared-lay structure. All FeII sites are six coordinated, and the FeeO bond distances are in the scope of 2.475(2) to 2.687(2) Å. The oxalate ligands feature two kinds of coordination modes: the first coordinates to three FeII ions in h1:h1:h1:h1:m3-bridging mode; the second connects two FeII ions in h1:h0:h1:h0:m2-bridging mode (Fig. 2a). The detailed bond valence sum (BVS) implies the existence of FeII (Table S2). The first kind of oxalate ligands connect FeII ions to form the 2D layers, while the second kind of oxalate ligands serve as pillars to connect FeII ions of adjacent layers (Fig. 2b). The strict arrangement of pillar and layer lead to the resultant anionic structure with NHþ 4 and H2O residing in the interlayers. Interestingly, there are 15-membered iron-organic rings in the 2D layer formed by FeII and h1:h1:h1:h1:m3-oxalate (Fig. S1). The framework
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of 2 is isostructural to the very recently reported iron oxalate K4Na2[Fe(C2O4)2]3$2H2O with Kþ and Naþ as the counterions [42]. Compared to those heterometallic-oxalate compounds by Descurtins and coworkers [43,44], the bridging modes of oxalate ligands in 2 are unique. Only the familiar h1:h1:h1:h1:m2-bridging mode of oxalate ligand was found in the aforementioned literature, while there are two kinds of bridging modes (h1:h0:h1:h0:m2 and h1:h1:h1:h1:m3) were observed in compound 2. Moreover, compared with the dominant FeIII-oxalate-based networks found in homometallic iron-oxalate family [6], the synthesis of FeII-oxalatebased architecture is also noteworthy. From the viewpoint of topology, the FeIIcenters coordinated to five oxalates could be treated as 5-connected nodes, while the m3-bridging oxalate could be viewed as 3-connected nodes. Therefore, the whole framework structure of 2 can be simplified as a binodal (3, 5)-connected hms €fli) symbol (63) (69$8) calculated with TOPOS net with point (Schla (Fig. 2c) [38]. It is worth noting that the pillared layer structure of 2 was fabricated by the single ligand, which is different from the known ones generated from mixed ligands [45e47]. The successful preparation of 2 not only adds a new member to the pillared-layer structure family, but also corroborates the feasibility of solvent-free synthesis in the creation of novel metal carboxylate architecture. 3.3. Thermal stability TGA were performed to study the thermal stabilities of 1 and 2. As shown in Fig. 3, the TGA diagram of 1 reveals that no weight loss can be found from room temperature to about 300 C, indicative of the good thermal stabilities of compound 1. Further heating above 300 C leads to the collapse of the framework structure. A weight loss of 52.22% was observed between 300 C and 650 C, corresponding to the departure of one ammonia and two oxalate (calculated: 53.82%). As for 2, no weight loss could be found between room temperature and 180 C, and the framework structure of 2 began to collapse above 200 C. A two-step weight loss of 64.60% is observed between 200 C and 550 C, indicative of the decomposition of two ammonia, one water, half oxalate and one oxalic acid (calculated: 65.08%). The remaining residue for 1 and 2 is amorphous after calcination respectively, and their phases are unidentified. 3.4. Magnetic studies To testify the phase purities of compounds 1 and 2 before thermal and magnetic measurements, PXRD (powder X-ray diffraction) analyses were conducted. As shown in Figs. S2 and S3, the experimental PXRD patterns match well with the simulated ones derived from the single-crystal structures, indicating the phase purities of the samples. Crushed crystalline samples of 1 and 2 were used for the magnetic characterization. The magnetic
Fig. 1. The coordination modes of FeII and LiI ions and oxalate in 1 (a); the 3D framework of 1 (b) (C in light green, O in red, N in blue, Li in turquiose, Fe in pink); the pto topology of 1 (c). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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Fig. 2. The coordination modes of FeII ions and oxalate in 2 (a); the pillared layer structure of 2 (C in light green, O in red, Fe in pink and the free NHþ 4 and H2O molecules omitted for clarity) (b); the hms topology of 2 (c). Symmetry code: A, x, y, 1 þ z; B, 1 e y, 1 þ x e y, z; C, 1 e x þ y, 1 e x, z; D, y, x, 1 e z; E, y, x, ez. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 3. TG plot for compounds 1 and 2.
susceptibility (c) was gauged in the temperature range 2e300 K at a field of 1000 Oe and the isothermal field-dependent magnetizations M(H) was measured at 2 K with fields up to 70 kOe. As
delineated in Fig. 4a, the cMT product of compound 1 at 300 K is 3.71 cm3 K mol1, which is larger than the spin-only values (3.0 cm3 K mol1, S ¼ 2, g ¼ 2.0) expected for one isolated high-spin d6 ions (3.0 cm3 K mol1), due to the spin-orbital couplings of octahedral FeII ions. On cooling, cMT declines gradually from 300 K to 50 K, followed by an obvious decrease to the minimum value of 0.70 cm3 K mol1 at 2 K. Fitting the magnetic data by CurieeWeiss law affords Curie constant C ¼ 3.81 cm3 K mol1 and Weiss constant q ¼ 2.06 K. It is notable that the small negative Weiss constant could not indicate the antiferromagnetic (AF) behavior of 1 because the strong spin-orbital coupling of octahedral FeII ions could also contribute to the negative Weiss constant. Actually, because of the isolation of LiI ions, the distance of nearest adjacent FeII is 2.191(6) Å, therefore, weak magnetic exchange interaction could be expected between neighboring FeII ions. The fielddependent magnetizations at 2 K feature a quasi-linear increasing trend along with the increasing fields and final reaches 2.73 Nb at 7 T, which is lower than the saturated value 4.0 Nb calculated with g ¼ 2.0 and S ¼ 2.0 (Fig. 4c). For compound 2, the observed cMT value of 3.67 cm3 kmol1 at 300 K is larger than the spin-only values (3.0 cm3 kmol1, S ¼ 2, g ¼ 2.0) anticipated for one high-spin d6 ions (Fig. 4b), indicating the non-neglectable contribution of the orbital contributions of the octahedral FeII ions. As the temperature is lowered, cMT exhibits a slow decrease from 300 K to 50 K and then an obvious decline to
Fig. 4. Plots ofcMT vs. T and c1 M vsT for 1 (a) and 2 (b) (red solid line stands for the CurieeWeiss fitting); the M vs. H plots for 1 (c) and 2 (d) measured at 2 K. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
J.-H. Li et al. / Solid State Sciences 48 (2015) 225e229
the minimum value of 0.36 cm3 K mol1 at 2 K. The magnetic data between 50 K and 300 K could be well fitted by CurieeWeiss law, yielding the Curie constant C ¼ 3.84 cm3 K mol1 and Weiss constant q ¼ 5.87 K. Notable, the relatively small negative Weiss constant could not derive the AF behavior of 2 because the spinorbital coupling of FeII ions also makes a contribution to the negative q value. In the pillared-layer structure of 2, the magnetic couplings are mainly transmitted by the intralayer h1:h1:h1:h1:m3oxalate, which could be viewed as the combination two syn,anticarboxylate. The syn,anti-carboxylate usually mediate weak magnetic exchange interactions in literature [48]. Thus, weak magnetic couplings among intralayer FeII ions are anticipated. As described in Fig. 4d, the field-dependent magnetizations at 2 K display a steady increase trend along with the increasing fields and final reaches 2.73 Nb at 7 T, which is lower than the theoretical value of 4.0 Nb for one FeII (g ¼ 2, S ¼ 2). 4. Conclusion In summary, two novel FeII-oxalate frameworks have been prepared by an oxalic acid flux approach and structurally characterized. Heterometallic compound 1 possesses a 3D framework structure with a pto topology composed of 3-connected metal units and 4-connected square rigid tetradentate oxalate units, which is different from the reported pto net comprised of 4-connected square metal-carboxylate units and 3-connected triangular carboxylate units. Homometallic compound 2 exhibits a pillarlayered architecture built from single ligand, which is distinct from the known pillared-layer architectures fabricated from mixed ligands. Thermal analysis suggests that 1 and 2 can stable up to 300 C and 200 C, respectively. Magnetic measurements indicate that weak magnetic exchange interactions exist in 1 and 2. The successful preparation of 1 and 2 not only enriches the existing field of metal carboxylate architecture, but also provides opportunities for the discovery of new metal carboxylate framework with interesting structures and properties via solvent-free synthesis. Related works are underway, including the investigation of their other properties, as well as an extension of this synthetic strategy into other Fe-based systems, aiming at creating novel open framework with various topologies and fascinating functionalities. Acknowledgments This work was supported by the Natural Science Foundation of China (21571111), a project of Shandong Province Higher Educational Science and Technology Program (J13LD18), a development project of Qingdao Science and Technology (13-1-4-187-jch) and the Taishan Scholar Program. Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.solidstatesciences.2015.08.017. References [1] H. Fei, S.M. Cohen, J. Am, Chem. Soc. 137 (2015) 2191. [2] Z.-Y. Gu, X.-P. Yan, Angew. Chem. Int. 49 (2010) 1477. rey, [3] P. Horcajada, C. Serre, M. Vallet-Regí, M. Sebban, F. Taulelle, G. Fe Angew.Chem. Int. 45 (2006) 5974. [4] A.C. McKinlay, P.K. Allan, C.L. Renouf, M.J. Duncan, P.S. Wheatley, S.J. Warrender, D. Dawson, S.E. Ashbrook, B. Gil, B. Marszalek, T. Düren, J.J. Williams, C. Charrier, D.K. Mercer, S.J. Teat, R.E. Morris, APL. Mat. 2 (2014) 124108. [5] A.C. McKinlay, B. Xiao, D.S. Wragg, P.S. Wheatley, I.L. Megson, R.E. Morris,
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J. Am, Chem. Soc. 130 (2008) 10440. [6] C.N.R. Rao, S. Natarajan, R. Vaidhyanathan, Angew. Chem. Int. 43 (2004) 1466. [7] C.-Y. Sun, X.-L. Wang, X. Zhang, C. Qin, P. Li, Z.-M. Su, D.-X. Zhu, G.-G. Shan, K.Z. Shao, H. Wu, J. Li, Nat. Commun. 4 (2013) 2717. [8] D.J. Xiao, E.D. Bloch, J.A. Mason, W.L. Queen, M.R. Hudson, N. Planas, J. Borycz, , J. Yano, S. Bordiga, A.L. Dzubak, P. Verma, K. Lee, F. Bonino, V. Crocella D.G. Truhlar, L. Gagliardi, C.M. Brown, J.R. Long, Nat. Chem. 6 (2014) 590. [9] G. de Combarieu, M. Morcrette, F. Millange, N. Guillou, J. Cabana, C.P. Grey, rey, J.M. Tarascon, Chem. Mater 21 (2009) 1602. I. Margiolaki, G. Fe [10] J.F. Eubank, P.S. Wheatley, G. Lebars, A.C. McKinlay, H. Leclerc, P. Horcajada, M. Daturi, A. Vimont, R.E. Morris, C. Serre, APL. Mat. 2 (2014) 124112. rey, F. Millange, M. Morcrette, C. Serre, M.-L. Doublet, J.-M. Grene che, J.[11] G. Fe M. Tarascon, Angew. Chem. Int. 46 (2007) 3259. [12] K.S. Hagen, S.G. Naik, B.H. Huynh, A. Masello, G. Christou, J. Am. Chem. Soc. 131 (2009) 7516. [13] P. Horcajada, T. Chalati, C. Serre, B. Gillet, C. Sebrie, T. Baati, J.F. Eubank, D. Heurtaux, P. Clayette, C. Kreuz, J.-S. Chang, Y.K. Hwang, V. Marsaud, P.N. Bories, L. Cynober, S. Gil, G. Ferey, P. Couvreur, R. Gref, Nat. Mater 9 (2010) 172. re, C.J. Nuttall, S.G. Carling, P. Day, Inorg.Chem. 35 (1996) 1201. [14] C. Mathonie [15] S.R. Miller, D. Heurtaux, T. Baati, P. Horcajada, J.-M. Greneche, C. Serre, Chem. Commun. 46 (2010) 4526. ~ adillas-Delgado, O. Fabelo, J.A. Rodríguez-Velamaza n, M.-H. Leme e[16] L. Can Cailleau, S.A. Mason, E. Pardo, F. Lloret, J.-P. Zhao, X.-H. Bu, V. Simonet, C.V. Colin, J. Rodríguez-Carvajal, J. Am. Chem. Soc. 134 (2012) 19772. [17] J.-P. Zhao, B.-W. Hu, F. Lloret, J. Tao, Q. Yang, X.-F. Zhang, X.-H. Bu, Inorg. Chem. 49 (2010) 10390. [18] Y.-W. Li, J.-P. Zhao, L.-F. Wang, X.-H. Bu, CrystEngComm 13 (2011) 6002. [19] M.-H. Zeng, X.-L. Feng, X.-M. Chen, Dalton Trans. (2004) 2217. [20] J.-B. Lin, R.-B. Lin, X.-N. Cheng, J.-P. Zhang, X.-M. Chen, Chem. Commun. 47 (2011) 9185. [21] M.J. Cliffe, C. Mottillo, R.S. Stein, D.-K. Bucar, T. Friscic, Chem. Sci. 3 (2012) 2495. [22] C. Duan, D. Luo, R. Shang, Z. Lin, CrystEngComm 15 (2013) 5602. [23] Z. Lin, H.P. Nayek, S. Dehnen, Inorg. Chem. 48 (2009) 3517. [24] A. Pichon, A. Lazuen-Garay, S.L. James, CrystEngComm 8 (2006) 211. [25] M.-R. Li, W. Liu, M.-H. Ge, H.-H. Chen, X.-X. Yang, J.-T. Zhao, Chem. Commun. (2004) 1272. [26] D.-B. Xiong, J.-T. Zhao, H.-H. Chen, X.-X. Yang, Chem.eEur. J. 13 (2007) 9862. [27] T. Yang, A. Bartoszewicz, J. Ju, J. Sun, Z. Liu, X. Zou, Y. Wang, G. Li, F. Liao, B. Martín-Matute, J. Lin, Angew. Chem. Int. 50 (2011) 12555. [28] J.-P. Zhao, S.-D. Han, X. Jiang, J. Xu, Z. Chang, X.-H. Bu, Chem. Commun. 51 (2015) 4627. [29] P.J. Calderone, D. Banerjee, L.A. Borkowski, J.B. Parise, Inorg. Chem. Commun. 14 (2011) 741. [30] A. Clough, S.-T. Zheng, X. Zhao, Q. Lin, P. Feng, X. Bu, Cryst. Growth Des. 14 (2014) 897. [31] L.-H. Xie, J.-B. Lin, X.-M. Liu, Y. Wang, W.-X. Zhang, J.-P. Zhang, X.-M. Chen, Inorg. Chem. 49 (2010) 1158. [32] T.-Z. Zhang, Z.-M. Zhang, Y. Lu, H. Fu, E.-B. Wang, CrystEngComm 15 (2013) 459. [33] Rigaku, Process-Auto, Rigaku Americas Corporation, The Woodlands, Texas, 1998. [34] G.M. Sheldrick, SHELXS97 Program for Solution of Crystal Structures, Uni€ ttingen, Go € ttingen, Germany, 1997. versity of Go [35] J.P. Declercq, J. Feneau-Dupont, J. Ladriere, Polyhedron 12 (1993) 1031. [36] J.P. Declercq, J. Feneau-Dupont, J. Ladriere, Polyhedron 14 (1995) 1943. [37] D. Armentano, T.F. Mastropietro, G. De Munno, P. Rossi, F. Lloret, M. Julve, Inorg. Chem. 47 (2008) 3772. [38] V.A. Blatov, TOPOS, A Multipurpose Crystallochemical Analysis with the Program Package, Samara State University, Russia, 2004. [39] S. Ma, D. Sun, M. Ambrogio, J.A. Fillinger, S. Parkin, H.-C. Zhou, J. Am, Chem. Soc. 129 (2007) 1858. [40] H. Furukawa, Y.B. Go, N. Ko, Y.K. Park, F.J. Uribe-Romo, J. Kim, M. O'Keeffe, O.M. Yaghi, Inorg. Chem. 50 (2011) 9147. [41] M. O'Keeffe, M.A. Peskov, S.J. Ramsden, O.M. Yaghi, Acc. Chem. Res. 41 (2008) 1782. [42] X. Wang, R. Kurono, S.-i. Nishimura, M. Okubo, A. Yamada, Chem. Eur. J. 21 (2015) 1096. [43] S. Decurtins, H.W. Schmalle, R. Pellaux, P. Schneuwly, A. Hauser, Inorg. Chem. 35 (1996) 1451. [44] R. Pellaux, H.W. Schmalle, R. Huber, P. Fischer, T. Hauss, B. Ouladdiaf, S. Decurtins, Inorg. Chem. 36 (1997) 2301. [45] Z. Chang, D.-S. Zhang, Q. Chen, R.-F. Li, T.-L. Hu, X.-H. Bu, Inorg. Chem. 50 (2011) 7555. [46] Q. Chen, Y.-Y. Jia, Z. Chang, T.-T. Wang, B.-Y. Zhou, R. Feng, X.-H. Bu, Cryst. Growth Des. 14 (2014) 5189. [47] Z.-H. Xuan, D.-S. Zhang, Z. Chang, T.-L. Hu, X.-H. Bu, Inorg. Chem. 53 (2014) 8985. [48] J.-P. Zhao, Q. Yang, Z.-Y. Liu, R. Zhao, B.-W. Hu, M. Du, Z. Chang, X.-H. Bu, Chem. Commun. 48 (2012) 6568.
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Two novel FeII-oxalate architectures: Solvent-free synthesis, structures, thermal and magnetic studies Jin-Hua Li a, **, Hui Liu b, Li Wei a, Guo-Ming Wang a, * a
College of Chemical Science and Engineering, Collaborative Innovation Center for Marine Biomass Fiber Materials and Textiles, Teachers College, Qingdao University, Shandong 266071, China b Department of Clinical Laboratory, Women and Children Hospital of Qingdao, Shandong 266034, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 1 July 2015 Received in revised form 6 August 2015 Accepted 20 August 2015 Available online 24 August 2015
Two novel FeII-oxalate framework with the formulas of [NH4][FeIILi3(C2O4)3] (1) and [NH4]2[FeII(C2O4)2]$ H2O (2) have been prepared by an oxalic acid flux approach and structurally characterized by IR, elemental analysis, thermogravimetric analysis, single-crystal and powder X-ray diffraction. Heterometallic compound 1 displays a three-dimensional (3D) framework with a pto topology, while homometallic compound 2 features a pillar-layer architecture with a hms topology. Thermal analysis indicates that the two compounds can be stable up to 300 C and 200 C, respectively. Magnetic investigations suggest that the FeII ions in 1 and 2 exhibit weak magnetic exchange interactions. © 2015 Elsevier Masson SAS. All rights reserved.
Keywords: Iron Oxalate Crystal structure Metal-carboxylate frameworks Topology
1. Introduction Metal carboxylates with open frameworks exhibits diverse structural chemistry and hold great promises in numerous areas such as catalysis, adsorption, separation, optics and drug release [1e8]. Owing to their low toxicity, environmental friendliness, interesting magnetism, and potential application in medicines and batteries, the iron carboxylates with open architectures attract considerable attention of researchers [9e17]. However, the rational design of such materials is still a challenging task for researchers due to the factor that the iron ions feature strong tendency of hydrolysis into stable polymeric iron oxide [18,19], which makes the preparation of targeted frameworks more difficult and usually give rise to precipitation rather than crystallization. Among the strategies to this goal, adopting sound synthetic methods to hinder the hydrolysis of iron ions is the key to create open framework ion carboxylates. A review of the available reference indicates that iron-carboxylates architectures are generally synthesized via solution-based syntheses [9e19]. Although the use
* Corresponding author. ** Corresponding author. E-mail addresses: [email protected] (J.-H. Li), [email protected] (G.-M. Wang). http://dx.doi.org/10.1016/j.solidstatesciences.2015.08.017 1293-2558/© 2015 Elsevier Masson SAS. All rights reserved.
of organic solvents could avoid the hydrolysis of iron ion to some extent, the organic solvents together with soluble salt usually restrict the final yield and generate a great deal of byproducts, which is not economic and environment-friendly [20]. By contrast, the new solvent-free syntheses possess several intrinsic merits over conventional solvent-based approach: low cost, easy handling, reducing pollution, and decreasing system pressure [21e24]. Moreover, novel open-framework structures with unique topologies may be generated by this approach because of the reduction or elimination of solvent-effect on the resulting structure [25e27]. Taking into account the points mentioned above, we attempted to explore the preparation of open framework iron oxalate via nonsolvent syntheses of FeCl3$6H2O, oxalic acid in the presence of urea and LiCl based on the following considerations: (a) oxalic acid with a relatively low melting point of 101.5 C is suitable for solvent-free flux synthesis, which could effectively avoid the hydrolysis of iron ion; (b) the rigid bidentate ligand oxalate can readily form extended frameworks by linking metal ions in various modes; (c) urea not only facilitates the deprotonation of oxalic acid but also decomposes in situ to generate ammonium (NHþ 4 ) as structure-directing agents under given conditions [28]; (d) extended networks containing the lightest elements lithium could be used to fabricate lightweight open framework with fascinating structures and properties [29e32].
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With these points in mind, we successfully isolated two novel Fe-oxalate framework with the formulas of [NH4][FeIILi3(C2O4)3] (1) and [NH4]2[FeII(C2O4)2]$H2O (2). The structures, topological analyses, thermal and magnetic properties of 1 and 2 have been thoroughly investigated. 2. Experimental section 2.1. Materials and methods All chemicals were of analytical grade (AR) and used as received. CHN analyses were performed on a PerkineElmer 240 C analyzer (PerkineElmer, USA). IR spectra were obtained from a MAGNA-560 (Nicolet) FT-IR spectrometer with KBr pellets. Powder X-ray diffraction (PXRD) spectra were collected on a Bruker D8 FOCUS diffractometer with a Cu-target tube and a graphite monochromator. The simulated PXRD spectra were generated from the single-crystal data via the Mercury (Hg) program that are freely available from the internet at http://www.iucr.org. The magnetic measurements were carried out on an MPMS XL-7 SQUID magnetometer. Diamagnetic corrections were estimated via utilizing Pascal constants and experimental corrections for the sample holder were applied. Thermogravimetric analyses (TGA) were conducted on a Rigaku standard TG-DTA analyzer with a heating rate of 10 C min1 from ambient temperature to 700 C under nitrogen gas. 2.2. Synthesis [NH4][FeIILi3(C2O4)3] (1). A mixture of FeCl3$6H2O (0.540 g, 2 mmol), H2C2O4$2H2O (2.520 g, 20 mmol), urea (0.600 g, 10 mmol), LiCl (0.340 g, 8 mmol)was sealed in a Teflon-lined autoclave (20 mL) and heated to 140 C for 72 h then slowly cooled to 30 C in 24 h. Yield: ca. 70% with respect to FeCl3$6H2O. Elemental analysis (%): Calcd. For C6H4NFeLi3O12 (358.76): C 20.09, N 3.90, H 1.12. Found: C 20.20, N 3.98, H 1.45. IR (KBr pellets, cm1): 3277(s), 2954(w), 1662(s), 1630(s), 1480(s), 1416(s), 1347(m), 1320(s), 913(w), 860(w), 811(s), 603(m), 480(s). [NH4]2[FeII(C2O4)2]$H2O (2). A mixture of FeCl3$6H2O (0.270 g, 1 mmol), H2C2O4$2H2O (1.260 g, 10 mmol), urea (0.300 g, 5 mmol), LiCl (0.170 g, 4 mmol) was sealed in a Teflon-lined autoclave (20 mL) and heated to 140 C for 72 h then slowly cooled to 30 C in 24 h. Yield: ca. 20% with respect to FeCl3$6H2O. Elemental analysis (%): Calcd. for C4H10N2FeO9 (285.98): C 16.80, N 9.80, H 3.52. Found: C 16.53, N 10.16, H 3.85. IR (KBr pellets, cm1): 3546(s), 3311(s), 3159(s), 3069(s), 2353(w), 1666(s), 1617(s), 1424(s), 1308(s), 904(w), 861(w), 784(s), 770(s), 612(m), 510(s). 2.3. Determination of crystal structure The single-crystal X-ray diffraction data for compounds 1 and 2 were collected on a Rigaku SCX-mini diffractometer at 293(2) K with Mo-Ka radiation (l ¼ 0.71073 Å) by uscan mode. The program CrystalClear was used for the integration of the diffraction profiles [33]. All structures were solved by direct method using the SHELXS program of the SHELXTL package and refined by full-matrix leastsquares methods with SHELXL (semi-empirical absorption corrections were applied by using the SADABS program) [34]. Heavy metal atoms in each compound were located from the E-maps and other non-hydrogen atoms were located in successive difference Fourier syntheses and refined with anisotropic thermal parameters. The hydrogen atoms of ammonium and the free water were not added and included directly in the molecular formula. Detailed crystallographic data are summarized in Table 1 and the selected bond lengths and angles are given in Tables S3 and S4. Full
Table 1 Crystal data and structure refinement parameters for compounds 1 and 2. 1 Formula Mr (g mol1) Space group Crystal system a (Å) b (Å) c (Å) a( ) b( ) g( ) V (Å3) Z F(000) Dc (g cm3) m (mm1) Rint limiting indices
C6H4NFeLi3O12 358.76 Re3c Trigonal 11.5273(16) 11.5273(16) 15.169(3) 90 90 120 1745.5(5) 6 1068 2.048 1.367 0.1028 13 h 13 13 k 13 18 l 18 Collected reflections 4574 Unique reflections 345 GOF on F2 1.211 R1,wR2[I > 2s(I)]a 0.05600.1246 R1,wR2 [all data]b 0.05940.1271 P P P P a R1 ¼ jjFoj-jFcjj/ jFoj.bwR2 ¼ { [w(F2o- F2c )2]/ w(F2o)2}1/2.
2 C4H10N2FeO9 285.98 P321 Trigonal 10.2055(14) 10.2055(14) 7.3773(15) 90 90 120 665.42(19) 3 438 2.141 1.747 0.0338 13 h 13 13 k 13 9 l 9 7061 1027 1.302 0.06340.1675 0.06420.1679
crystallographic data for 1 and 2 have been deposited with the CCDC number 1405302 for 1 and 1405301 for 2. These data can be freely available from the Cambridge Crystallographic Data Centre at www.ccdc.cam.ac.uk/data_request/cif. 3. Results and discussion 3.1. Syntheses It is notable that the urea plays an important role in the formation of 1 and 2. Firstly, the basic urea promoted the generation of deprotonated oxalic acid. Secondly, the in situ decomposition of urea offers ammonia that could provide more basic conditions, which were helpful for the fabrication of high dimensional frameworks by further deprotonation of oxalic acid. Thirdly, the in situ generated NHþ 4 originated from the protonated ammonia could not only act as a counter cation but also the structure-directing agents to guide the fabrication of anionic open frameworks with special structures and properties. Interestingly, when the amount of reactants for 1 was reduced by a factor of two, compounds 1 and 2 formed together. However, further reducing the amount of reactants by a factor of three or four could not obtain 1 and 2. Attempts to prepare 2 with FeCl3$6H2O, H2C2O4$2H2O and urea in the absence of LiCl were fruitless, and we believe LiCl may play an important and subtle role in the crystallization process of 2. The FeII ions in 1 and 2 may come from the reduction of FeIII by oxalic acid. The reduction of FeIII to FeII ions has been reported in formate system [16,17]. 3.2. Structural description Crystallographic studies revealed that compound 1 crystallizes in a trigonal system with space group Re3c. Its structure consists of the [FeIILi3(C2O4)3]anionic framework, and NHþ 4 ions exist in the 1D channels to balance the negative charges. All FeII and LiI sites are six coordinated. All oxalate ligands are in h2:h2:h2:h2:m4-bridging mode to link one FeII and three LiI ions. The detailed bond valence sum (BVS) indicates that all iron ions are FeII (Table S1). The Fe1
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center displays an octahedral [FeO6] geometry formed by the coordination of six symmetry-related O1 atoms from three symmetry-related oxalate ligands (Fig. 1a). The Li1 center exhibits a distorted octahedral [LiO6] geometry formed by the coordination of four symmetry-related O1and two symmetry-related O2 atoms from three symmetry-related oxalate ligands (Fig. 1a). The FeeO bond distances are 2.191(6) Å, while the LieO bond distances range from 2.475(2) to 2.687(2) Å. Each FeII connects nine adjacent LiI ions via three oxalate ligands, and each LiI links three neighboring FeII and six adjacent LiI ions by three oxalate ligands. The strictly alternative arrangement of FeII and LiI gives rise to the final 3D framework of 1. It is worthy to note that the resultant architecture is distinct from the reported heterometallic FeIIIeLiI oxalate compounds [35,36], in which the Li ions with two types of coordination modes (i.e. octahedron and tetrahedron) participated in the formation of the framework. In addition, owing to the reduction of FeIII by oxalic acid, the bond valance of iron in 1 is þ 2, which is also different from other FeIIIeLi heterometallic oxalate network [35e37]. There has 1D channel in the structure of 1, which is þ partially occluded by NHþ 4 (Fig. 1b). The hydrogen atoms of NH4 form H-bonds with the oxygen atoms of the anionic framework. Thus, it is reasonable for us to contend that the NHþ 4 acts as a template or structure-directing agent in the formation of 1. To better understand the framework of 1, it is necessary to simplify its structure from the topological viewpoint. The Fe/Li centers coordinated to three oxalates could be considered as 3-connected nodes, while the m4-bridging oxalate could be viewed as 4connected nodes. Therefore, the whole 3D structure can be ratio€fli) nalized as a binodal (3,4)-connected pto net with point (Schla symbol (83)4(86)3 calculated with TOPOS (Fig. 1c) [38]. Interestingly, distinct from the reported pto net composed of 4-connected square-planar metal-carboxylate units and 3-connected triangular carboxylate units [39e41], the pto net of 1 was comprised of 3connected metal units and 4-connected square rigid tetradentate oxalate units. Compound 2 crystallizes in a trigonal system with space group P321. The anionic framework of 2 could be comprehended as a pillared-lay structure. All FeII sites are six coordinated, and the FeeO bond distances are in the scope of 2.475(2) to 2.687(2) Å. The oxalate ligands feature two kinds of coordination modes: the first coordinates to three FeII ions in h1:h1:h1:h1:m3-bridging mode; the second connects two FeII ions in h1:h0:h1:h0:m2-bridging mode (Fig. 2a). The detailed bond valence sum (BVS) implies the existence of FeII (Table S2). The first kind of oxalate ligands connect FeII ions to form the 2D layers, while the second kind of oxalate ligands serve as pillars to connect FeII ions of adjacent layers (Fig. 2b). The strict arrangement of pillar and layer lead to the resultant anionic structure with NHþ 4 and H2O residing in the interlayers. Interestingly, there are 15-membered iron-organic rings in the 2D layer formed by FeII and h1:h1:h1:h1:m3-oxalate (Fig. S1). The framework
227
of 2 is isostructural to the very recently reported iron oxalate K4Na2[Fe(C2O4)2]3$2H2O with Kþ and Naþ as the counterions [42]. Compared to those heterometallic-oxalate compounds by Descurtins and coworkers [43,44], the bridging modes of oxalate ligands in 2 are unique. Only the familiar h1:h1:h1:h1:m2-bridging mode of oxalate ligand was found in the aforementioned literature, while there are two kinds of bridging modes (h1:h0:h1:h0:m2 and h1:h1:h1:h1:m3) were observed in compound 2. Moreover, compared with the dominant FeIII-oxalate-based networks found in homometallic iron-oxalate family [6], the synthesis of FeII-oxalatebased architecture is also noteworthy. From the viewpoint of topology, the FeIIcenters coordinated to five oxalates could be treated as 5-connected nodes, while the m3-bridging oxalate could be viewed as 3-connected nodes. Therefore, the whole framework structure of 2 can be simplified as a binodal (3, 5)-connected hms €fli) symbol (63) (69$8) calculated with TOPOS net with point (Schla (Fig. 2c) [38]. It is worth noting that the pillared layer structure of 2 was fabricated by the single ligand, which is different from the known ones generated from mixed ligands [45e47]. The successful preparation of 2 not only adds a new member to the pillared-layer structure family, but also corroborates the feasibility of solvent-free synthesis in the creation of novel metal carboxylate architecture. 3.3. Thermal stability TGA were performed to study the thermal stabilities of 1 and 2. As shown in Fig. 3, the TGA diagram of 1 reveals that no weight loss can be found from room temperature to about 300 C, indicative of the good thermal stabilities of compound 1. Further heating above 300 C leads to the collapse of the framework structure. A weight loss of 52.22% was observed between 300 C and 650 C, corresponding to the departure of one ammonia and two oxalate (calculated: 53.82%). As for 2, no weight loss could be found between room temperature and 180 C, and the framework structure of 2 began to collapse above 200 C. A two-step weight loss of 64.60% is observed between 200 C and 550 C, indicative of the decomposition of two ammonia, one water, half oxalate and one oxalic acid (calculated: 65.08%). The remaining residue for 1 and 2 is amorphous after calcination respectively, and their phases are unidentified. 3.4. Magnetic studies To testify the phase purities of compounds 1 and 2 before thermal and magnetic measurements, PXRD (powder X-ray diffraction) analyses were conducted. As shown in Figs. S2 and S3, the experimental PXRD patterns match well with the simulated ones derived from the single-crystal structures, indicating the phase purities of the samples. Crushed crystalline samples of 1 and 2 were used for the magnetic characterization. The magnetic
Fig. 1. The coordination modes of FeII and LiI ions and oxalate in 1 (a); the 3D framework of 1 (b) (C in light green, O in red, N in blue, Li in turquiose, Fe in pink); the pto topology of 1 (c). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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Fig. 2. The coordination modes of FeII ions and oxalate in 2 (a); the pillared layer structure of 2 (C in light green, O in red, Fe in pink and the free NHþ 4 and H2O molecules omitted for clarity) (b); the hms topology of 2 (c). Symmetry code: A, x, y, 1 þ z; B, 1 e y, 1 þ x e y, z; C, 1 e x þ y, 1 e x, z; D, y, x, 1 e z; E, y, x, ez. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 3. TG plot for compounds 1 and 2.
susceptibility (c) was gauged in the temperature range 2e300 K at a field of 1000 Oe and the isothermal field-dependent magnetizations M(H) was measured at 2 K with fields up to 70 kOe. As
delineated in Fig. 4a, the cMT product of compound 1 at 300 K is 3.71 cm3 K mol1, which is larger than the spin-only values (3.0 cm3 K mol1, S ¼ 2, g ¼ 2.0) expected for one isolated high-spin d6 ions (3.0 cm3 K mol1), due to the spin-orbital couplings of octahedral FeII ions. On cooling, cMT declines gradually from 300 K to 50 K, followed by an obvious decrease to the minimum value of 0.70 cm3 K mol1 at 2 K. Fitting the magnetic data by CurieeWeiss law affords Curie constant C ¼ 3.81 cm3 K mol1 and Weiss constant q ¼ 2.06 K. It is notable that the small negative Weiss constant could not indicate the antiferromagnetic (AF) behavior of 1 because the strong spin-orbital coupling of octahedral FeII ions could also contribute to the negative Weiss constant. Actually, because of the isolation of LiI ions, the distance of nearest adjacent FeII is 2.191(6) Å, therefore, weak magnetic exchange interaction could be expected between neighboring FeII ions. The fielddependent magnetizations at 2 K feature a quasi-linear increasing trend along with the increasing fields and final reaches 2.73 Nb at 7 T, which is lower than the saturated value 4.0 Nb calculated with g ¼ 2.0 and S ¼ 2.0 (Fig. 4c). For compound 2, the observed cMT value of 3.67 cm3 kmol1 at 300 K is larger than the spin-only values (3.0 cm3 kmol1, S ¼ 2, g ¼ 2.0) anticipated for one high-spin d6 ions (Fig. 4b), indicating the non-neglectable contribution of the orbital contributions of the octahedral FeII ions. As the temperature is lowered, cMT exhibits a slow decrease from 300 K to 50 K and then an obvious decline to
Fig. 4. Plots ofcMT vs. T and c1 M vsT for 1 (a) and 2 (b) (red solid line stands for the CurieeWeiss fitting); the M vs. H plots for 1 (c) and 2 (d) measured at 2 K. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
J.-H. Li et al. / Solid State Sciences 48 (2015) 225e229
the minimum value of 0.36 cm3 K mol1 at 2 K. The magnetic data between 50 K and 300 K could be well fitted by CurieeWeiss law, yielding the Curie constant C ¼ 3.84 cm3 K mol1 and Weiss constant q ¼ 5.87 K. Notable, the relatively small negative Weiss constant could not derive the AF behavior of 2 because the spinorbital coupling of FeII ions also makes a contribution to the negative q value. In the pillared-layer structure of 2, the magnetic couplings are mainly transmitted by the intralayer h1:h1:h1:h1:m3oxalate, which could be viewed as the combination two syn,anticarboxylate. The syn,anti-carboxylate usually mediate weak magnetic exchange interactions in literature [48]. Thus, weak magnetic couplings among intralayer FeII ions are anticipated. As described in Fig. 4d, the field-dependent magnetizations at 2 K display a steady increase trend along with the increasing fields and final reaches 2.73 Nb at 7 T, which is lower than the theoretical value of 4.0 Nb for one FeII (g ¼ 2, S ¼ 2). 4. Conclusion In summary, two novel FeII-oxalate frameworks have been prepared by an oxalic acid flux approach and structurally characterized. Heterometallic compound 1 possesses a 3D framework structure with a pto topology composed of 3-connected metal units and 4-connected square rigid tetradentate oxalate units, which is different from the reported pto net comprised of 4-connected square metal-carboxylate units and 3-connected triangular carboxylate units. Homometallic compound 2 exhibits a pillarlayered architecture built from single ligand, which is distinct from the known pillared-layer architectures fabricated from mixed ligands. Thermal analysis suggests that 1 and 2 can stable up to 300 C and 200 C, respectively. Magnetic measurements indicate that weak magnetic exchange interactions exist in 1 and 2. The successful preparation of 1 and 2 not only enriches the existing field of metal carboxylate architecture, but also provides opportunities for the discovery of new metal carboxylate framework with interesting structures and properties via solvent-free synthesis. Related works are underway, including the investigation of their other properties, as well as an extension of this synthetic strategy into other Fe-based systems, aiming at creating novel open framework with various topologies and fascinating functionalities. Acknowledgments This work was supported by the Natural Science Foundation of China (21571111), a project of Shandong Province Higher Educational Science and Technology Program (J13LD18), a development project of Qingdao Science and Technology (13-1-4-187-jch) and the Taishan Scholar Program. Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.solidstatesciences.2015.08.017. References [1] H. Fei, S.M. Cohen, J. Am, Chem. Soc. 137 (2015) 2191. [2] Z.-Y. Gu, X.-P. Yan, Angew. Chem. Int. 49 (2010) 1477. rey, [3] P. Horcajada, C. Serre, M. Vallet-Regí, M. Sebban, F. Taulelle, G. Fe Angew.Chem. Int. 45 (2006) 5974. [4] A.C. McKinlay, P.K. Allan, C.L. Renouf, M.J. Duncan, P.S. Wheatley, S.J. Warrender, D. Dawson, S.E. Ashbrook, B. Gil, B. Marszalek, T. Düren, J.J. Williams, C. Charrier, D.K. Mercer, S.J. Teat, R.E. Morris, APL. Mat. 2 (2014) 124108. [5] A.C. McKinlay, B. Xiao, D.S. Wragg, P.S. Wheatley, I.L. Megson, R.E. Morris,
229
J. Am, Chem. Soc. 130 (2008) 10440. [6] C.N.R. Rao, S. Natarajan, R. Vaidhyanathan, Angew. Chem. Int. 43 (2004) 1466. [7] C.-Y. Sun, X.-L. Wang, X. Zhang, C. Qin, P. Li, Z.-M. Su, D.-X. Zhu, G.-G. Shan, K.Z. Shao, H. Wu, J. Li, Nat. Commun. 4 (2013) 2717. [8] D.J. Xiao, E.D. Bloch, J.A. Mason, W.L. Queen, M.R. Hudson, N. Planas, J. Borycz, , J. Yano, S. Bordiga, A.L. Dzubak, P. Verma, K. Lee, F. Bonino, V. Crocella D.G. Truhlar, L. Gagliardi, C.M. Brown, J.R. Long, Nat. Chem. 6 (2014) 590. [9] G. de Combarieu, M. Morcrette, F. Millange, N. Guillou, J. Cabana, C.P. Grey, rey, J.M. Tarascon, Chem. Mater 21 (2009) 1602. I. Margiolaki, G. Fe [10] J.F. Eubank, P.S. Wheatley, G. Lebars, A.C. McKinlay, H. Leclerc, P. Horcajada, M. Daturi, A. Vimont, R.E. Morris, C. Serre, APL. Mat. 2 (2014) 124112. rey, F. Millange, M. Morcrette, C. Serre, M.-L. Doublet, J.-M. Grene che, J.[11] G. Fe M. Tarascon, Angew. Chem. Int. 46 (2007) 3259. [12] K.S. Hagen, S.G. Naik, B.H. Huynh, A. Masello, G. Christou, J. Am. Chem. Soc. 131 (2009) 7516. [13] P. Horcajada, T. Chalati, C. Serre, B. Gillet, C. Sebrie, T. Baati, J.F. Eubank, D. Heurtaux, P. Clayette, C. Kreuz, J.-S. Chang, Y.K. Hwang, V. Marsaud, P.N. Bories, L. Cynober, S. Gil, G. Ferey, P. Couvreur, R. Gref, Nat. Mater 9 (2010) 172. re, C.J. Nuttall, S.G. Carling, P. Day, Inorg.Chem. 35 (1996) 1201. [14] C. Mathonie [15] S.R. Miller, D. Heurtaux, T. Baati, P. Horcajada, J.-M. Greneche, C. Serre, Chem. Commun. 46 (2010) 4526. ~ adillas-Delgado, O. Fabelo, J.A. Rodríguez-Velamaza n, M.-H. Leme e[16] L. Can Cailleau, S.A. Mason, E. Pardo, F. Lloret, J.-P. Zhao, X.-H. Bu, V. Simonet, C.V. Colin, J. Rodríguez-Carvajal, J. Am. Chem. Soc. 134 (2012) 19772. [17] J.-P. Zhao, B.-W. Hu, F. Lloret, J. Tao, Q. Yang, X.-F. Zhang, X.-H. Bu, Inorg. Chem. 49 (2010) 10390. [18] Y.-W. Li, J.-P. Zhao, L.-F. Wang, X.-H. Bu, CrystEngComm 13 (2011) 6002. [19] M.-H. Zeng, X.-L. Feng, X.-M. Chen, Dalton Trans. (2004) 2217. [20] J.-B. Lin, R.-B. Lin, X.-N. Cheng, J.-P. Zhang, X.-M. Chen, Chem. Commun. 47 (2011) 9185. [21] M.J. Cliffe, C. Mottillo, R.S. Stein, D.-K. Bucar, T. Friscic, Chem. Sci. 3 (2012) 2495. [22] C. Duan, D. Luo, R. Shang, Z. Lin, CrystEngComm 15 (2013) 5602. [23] Z. Lin, H.P. Nayek, S. Dehnen, Inorg. Chem. 48 (2009) 3517. [24] A. Pichon, A. Lazuen-Garay, S.L. James, CrystEngComm 8 (2006) 211. [25] M.-R. Li, W. Liu, M.-H. Ge, H.-H. Chen, X.-X. Yang, J.-T. Zhao, Chem. Commun. (2004) 1272. [26] D.-B. Xiong, J.-T. Zhao, H.-H. Chen, X.-X. Yang, Chem.eEur. J. 13 (2007) 9862. [27] T. Yang, A. Bartoszewicz, J. Ju, J. Sun, Z. Liu, X. Zou, Y. Wang, G. Li, F. Liao, B. Martín-Matute, J. Lin, Angew. Chem. Int. 50 (2011) 12555. [28] J.-P. Zhao, S.-D. Han, X. Jiang, J. Xu, Z. Chang, X.-H. Bu, Chem. Commun. 51 (2015) 4627. [29] P.J. Calderone, D. Banerjee, L.A. Borkowski, J.B. Parise, Inorg. Chem. Commun. 14 (2011) 741. [30] A. Clough, S.-T. Zheng, X. Zhao, Q. Lin, P. Feng, X. Bu, Cryst. Growth Des. 14 (2014) 897. [31] L.-H. Xie, J.-B. Lin, X.-M. Liu, Y. Wang, W.-X. Zhang, J.-P. Zhang, X.-M. Chen, Inorg. Chem. 49 (2010) 1158. [32] T.-Z. Zhang, Z.-M. Zhang, Y. Lu, H. Fu, E.-B. Wang, CrystEngComm 15 (2013) 459. [33] Rigaku, Process-Auto, Rigaku Americas Corporation, The Woodlands, Texas, 1998. [34] G.M. Sheldrick, SHELXS97 Program for Solution of Crystal Structures, Uni€ ttingen, Go € ttingen, Germany, 1997. versity of Go [35] J.P. Declercq, J. Feneau-Dupont, J. Ladriere, Polyhedron 12 (1993) 1031. [36] J.P. Declercq, J. Feneau-Dupont, J. Ladriere, Polyhedron 14 (1995) 1943. [37] D. Armentano, T.F. Mastropietro, G. De Munno, P. Rossi, F. Lloret, M. Julve, Inorg. Chem. 47 (2008) 3772. [38] V.A. Blatov, TOPOS, A Multipurpose Crystallochemical Analysis with the Program Package, Samara State University, Russia, 2004. [39] S. Ma, D. Sun, M. Ambrogio, J.A. Fillinger, S. Parkin, H.-C. Zhou, J. Am, Chem. Soc. 129 (2007) 1858. [40] H. Furukawa, Y.B. Go, N. Ko, Y.K. Park, F.J. Uribe-Romo, J. Kim, M. O'Keeffe, O.M. Yaghi, Inorg. Chem. 50 (2011) 9147. [41] M. O'Keeffe, M.A. Peskov, S.J. Ramsden, O.M. Yaghi, Acc. Chem. Res. 41 (2008) 1782. [42] X. Wang, R. Kurono, S.-i. Nishimura, M. Okubo, A. Yamada, Chem. Eur. J. 21 (2015) 1096. [43] S. Decurtins, H.W. Schmalle, R. Pellaux, P. Schneuwly, A. Hauser, Inorg. Chem. 35 (1996) 1451. [44] R. Pellaux, H.W. Schmalle, R. Huber, P. Fischer, T. Hauss, B. Ouladdiaf, S. Decurtins, Inorg. Chem. 36 (1997) 2301. [45] Z. Chang, D.-S. Zhang, Q. Chen, R.-F. Li, T.-L. Hu, X.-H. Bu, Inorg. Chem. 50 (2011) 7555. [46] Q. Chen, Y.-Y. Jia, Z. Chang, T.-T. Wang, B.-Y. Zhou, R. Feng, X.-H. Bu, Cryst. Growth Des. 14 (2014) 5189. [47] Z.-H. Xuan, D.-S. Zhang, Z. Chang, T.-L. Hu, X.-H. Bu, Inorg. Chem. 53 (2014) 8985. [48] J.-P. Zhao, Q. Yang, Z.-Y. Liu, R. Zhao, B.-W. Hu, M. Du, Z. Chang, X.-H. Bu, Chem. Commun. 48 (2012) 6568.