Incomplete Spin Crossover versus Antiferromagnetic Behavior

Article pubs.acs.org/crystal

Incomplete Spin Crossover versus Antiferromagnetic Behavior Exhibited in Three-Dimensional Porous Fe(II)-Bis(tetrazolate) Frameworks Wen-Ting Liu, Jin-Yan Li, Zhao-Ping Ni, Xin Bao, Yong-Cong Ou, Ji-Dong Leng, Jun-Liang Liu, and Ming-Liang Tong* Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education, State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, China S Supporting Information *

ABSTRACT: Two three-dimensional (3D) Fe(II) porous metal−organic frameworks (MOFs) [Fe2(H0.67bdt)3]·13H2O (1·13H2O) and [Fe3(ox)(H0.67bdt)3(H2O)2]·solvent (2·solvent) (H2bdt = 5,5′-(1,4-phenylene)bis(1H-tetrazole); H2ox = oxalic acid; solvent = 10H2O and 9CH3OH for 2·9MeOH and 6H2O and 5C4H9OH for 2·5n-BuOH) were solvothermally synthesized and characterized. The X-ray structure analysis reveals that complex 1·13H2O is constructed from one-dimensional (1D) {Fe(tz)3}n (tz = tetrazolate) chains which are linked through the phenyl tethers of the bdt ligands into a 3D microporous framework. In the case of complex 2·solvent, the linear trinuclear [Fe3(tz)6] units are linked by ox2− bridges to form 1D {Fe3(tz)6(ox)}n chains, which are also extended into a 3D microporous framework linked by the bdt ligands. Their frameworks can be simplified as the same topological network (46,66,83)(42,63,8). The substructure of the 1D {Fe(tz)3}n chain in 1·13H2O consists of spin-crossover (SCO) active Fe1 ions and low spin (LS) Fe2 ions alternately, while the trinuclear unit in 2·solvent contains a partial high spin (HS) Fe1 ion and two terminal HS Fe2 ions. Magnetic susceptibility measurements reveal that complex 1·13H2O presents an incomplete gradual SCO behavior. Although complex 2·solvent also has the SCO active Fe1 ions, the spin state change is extremely small and the antiferromagnetic property is primarily observed.

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INTRODUCTION Spin-crossover (SCO) materials are potentially useful for data storage and display devices due to their switching properities.1 Spin transition (ST) between high spin (HS) and low spin (LS) states can be driven by external stimuli such as temperature, pressure, or light.2 However, the sensitivity of SCO property to myriad solid state effects makes rational design frustrating. Some subtle changes, even in the secondary coordination sphere, may lead to completely different SCO behaviors or suppression of the occurrence of SCO. Much work remains to be done in order to explore structure−property correlations.1i,3d,3e Recent efforts have been devoted to introduce SCO active centers into porous metal−organic frameworks (MOFs). MOF materials are potential candidates for storage, separation, and heterogeneous catalysis due to their chemical versatility and porosity.3 This attempt may not only open up a powerful approach for exploiting multifunctional materials, but also provide chemists with a unique avenue for investigating the influence of absorbed guests on SCO property.4 Many different N-coordinating heterocyclic ligands are used for producing Fe(II) SCO compounds, such as triazoles,5 tetrazoles (tz),6 and imidazoles.7 In the SCO field, the design and synthesis of {FeN6}n chain compounds have been extensively investigated for a long time, because these compounds usually exhibit obvious spin crossover behavior © 2012 American Chemical Society

accompanied by distinct magnetic and color changes. These materials are usually based on Fe(II) and triazole-containing ligands, but they hardly crystallize.8 By now only one example of the crystal structure has been reported.9 As terminal or bridging ligands, the tetrazole-containing ligands can form mononuclear complexes,6a,10 one-dimensional (1D) chains,11 or three-dimensional (3D) networks.6b However, the {FeN6}n chain structure based on the tetrazole-containing ligand is rare. Until now, only one example of a chain compound with the (tetrazole-1-yl)propane ligand has been reported.11a The polyazaheteroaromatic ligands of the tetrazole ligands are quite attractive considering their extensively documented ability of bridging metal ions to form polynuclear compounds and their superexchange capacities reflected in unusual magnetic properties. Our strategy to construct the {Fe(tz)6}n chain is based on the H2bdt (5,5′-(1,4-phenylene)bis(1H-tetrazole)) ligand,12 which has never been applied to Fe(II) SCO compounds. Only a structural analogue [Co2(H0.67bdt)3]·20H2O has been reported, which exhibits single chain magnet behavior.12c Herein we report the crystal structures and magnetic properties of two 3D porous MOF materials in the Fe(II)/ Received: November 28, 2011 Revised: January 10, 2012 Published: January 18, 2012 1482

dx.doi.org/10.1021/cg201569m | Cryst. Growth Des. 2012, 12, 1482−1488

Crystal Growth & Design

Article

Table 1. Crystal Data and Structure Refinements for 1·13H2O empirical formula M wavelength (Å) crystal system space group a/Å c/Å vol/Å3 Z ρcalcd/g cm−3 μ/mm−1 reflns collected unique reflns S R1a, wR2b (I > 2σ(I)) (squeeze) R1a, wR2b (all data) (squeeze) a

100(2) K

150(2) K

200(2) K

298(2) K

C12H20N12O6.5Fe 492.25 0.71073 trigonal R3̅m 22.505(3) 7.3716(19) 3233.4(10) 6 1.517 0.758 2918 753(0.0297) 1.124 0.023, 0.1433 0.0564, 0.1473




R1 = ∑||Fo| − |Fc||/∑|Fo|. bwR2 = [∑w(Fo2 − Fc2)2/∑w(Fo2)2]1/2.

Table 2. Crystal Data and Structure Refinements for 2·9MeOH and 2·5n-BuOH empirical formula M wavelength (Å) crystal system space group a/Å b/Å c/Å β/° vol/Å3 Z ρcalcd/g cm−3 μ/mm−1 reflns collected unique reflns S R1a, wR2b (I > 2σ(I)) (squeeze) R1a, wR2b (all data) (squeeze) a

2·9MeOH 110(2) K

2·9MeOH 150(2) K

2·5n-BuOH 110(2) K

2·5n-BuOH 298(2) K

C35H74N24O25Fe3 1398.73 1.54178 monoclinic C2/m 12.078(2) 24.560(5) 12.087(2) 110.48(2) 3359.1(11) 2 1.383 5.891 4437 2540 (0.1015) 0.870 0.0666, 0.1400 0.0872, 0.1508




R1 = ∑||Fo| − |Fc||/∑|Fo|. bwR2 = [∑w(Fo2 − Fc2)2/∑w(Fo2)2]1/2. 4000−400 cm−1 on Bio-Rad FTS-7 spectrometer. Thermogravimetric (TG) analyses were carried out on NETZSCH TG209F3 thermogravimetric analyzer. X-ray powder diffraction (XPRD) intensities for polycrystalline samples of 1·13H2O, 2·9MeOH, and 2·5n-BuOH were measured at 293 K on Bruker D8 Advance diffractometer (CuKα, λ = 1.54056 Å) by scanning over the range of 5−60° with step of 0.2°/s. Simulated XPRD patterns of 1·13H2O and 2·9MeOH were generated with Mercury. Variable-temperature magnetic susceptibility measurements were carried out using SQUID magnetometer MPMS XL-7 (Quantum Design). Diamagnetic correction was applied from Pascal’s constants. Synthesis Methods. [Fe2(H0.67bdt)3]·13H2O (1·13H2O). A mixture solution of FeCl2·4H2O (0.013 g, 0.075 mmol), H2bdt (0.025 g, 0.1 mmol), K2CO3 (0.010 g, 0.07 mmol), and ascorbic acid (0.007 g, 0.04 mmol) in 8 mL of ethanol and water (12:1) was sealed in a 20 mL Teflon-lined reactor and heated at 160 °C for 72 h and then cooled to room temperature at 5 °C h−1 to give red blocked crystals of 1·13H2O (Yield: 22.9%, based on H2bdt). Elemental analysis calcd (%) C24H40O13N24Fe2: C, 29.28; H, 4.10; N, 34.15. found: C, 29.04; H, 4.32; N, 34.43. IR (KBr) (400−4000 cm−1): 3415vs,

H 2 bdt system [Fe 2 (H 0.67 bdt) 3 ]·13H 2 O (1·13H 2 O) and [Fe3(ox)(H0.67bdt)3(H2O)2]·solvent (2·solvent), where H2ox = oxalic acid; solvent = 10H2O and 9CH3OH for 2·9MeOH and 6H2O and 5C4H9OH for 2·5n-BuOH. Complex 1·13H2O contains the 1D {Fe(tz)}n chain, which is constructed by the SCO active Fe1 ions and LS Fe2 ions alternately. Magnetic measurement of 1·13H2O reveals an incomplete gradual spincrossover behavior. In the case of complex 2·solvent, the 1D [Fe3(tz)6(ox)]n chain consists of a partial high-spin (HS) Fe1 ion and two terminal HS Fe2 ions. However, the SCO active sites do not show any obvious spin state changes as the temperature decreases and complex 2·solvent primarily exhibits antiferromagnetic properties.

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EXPERIMENTAL SECTION

Materials and Physical Measurements. The reagents and solvents used were commercially available and used as received without further purification. C, H, and N microanalyses were carried out on fresh crystal samples with Elementar Vario-EL CHN elemental analyzer. FT-IR spectra were recorded in KBr tablets in the range 1483



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Figure 1. (a) Ball and stick drawing of the coordination environments of the Fe atoms and bdt ligand in 1·13H2O, pink, azure blue, blue, and gray spheres represent Fe1(HS), Fe2(LS), N, and C atoms, respectively; (b) the {Fe(tz)3}n chain substructure; (c) the linking of chains through the phenyl tether of the bdt ligand viewing along the c axis at room temperature; and (d) the topological network. Hydrogen atoms and lattice solvent molecules have been omitted for clarity.

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1636s, 1434s, 1201w, 1156w, 1061 m, 1011w, 752w, 606w, 543 m. [Fe3(ox)(H0.67bdt)3(H2O)2]·10H2O·9CH3OH (2·9MeOH). A mixture solution of FeCl2·4H2O (0.010 g, 0.05 mmol), H2bdt (0.025 g, 0.1 mmol), triethylamine (Et3N) (0.030 g, 0.3 mmol), and ascorbic acid (0.007 g, 0.04 mmol) in methanol (10 mL) was sealed in a 20 mL Teflon-lined reactor and heated at 160 °C for 3 days and then cooled to room temperature at 5 °C h−1. Small yellow crystals of 2·9MeOH (yield: 10%, based on H2bdt) were obtained. Elemental analysis Calcd (%) C35N24H74O25Fe3: C, 30.06; H, 5.33; N, 24.03. Found: C, 30.58; H, 5.52; N, 24.46. Infrared (KBr disk, cm−1): 3398vs, 1641vs, 1435s, 1010 m, 705 m, 542w, 491 m. [Fe3(ox)(H0.67bdt)3(H2O)2]·6H2O·5C4H9OH (2·5n-BuOH). When 2·9MeOH were soaked into n-butanol for 2 h, MeOH molecules were exchanged with n-butanol and the red crystals of 2·5n-BuOH were obtained. Elemental analysis calcd (%) C46N24H80O17Fe3: C, 39.22; H, 5.72; N, 23.86. Found: C, 39.43; H, 5.79; N, 24.20. X-ray Crystallography. Diffraction data for 1·13H2O, 2·9MeOH and 2·5n-BuOH were collected on Bruker Apex CCD area detector diffractometer (MoKα radiation, λ = 0.71073 Å), Oxford Diffraction Gemini R CCD diffractometer with CuKα radiation (λ = 1.54178 Å) or Rigaku R-AXIS SPIDER Image Plate diffractometer with graphitemonochromated MoKα radiation (λ = 0.71073 Å) (see Supporting Information). The measurement temperature was controlled using an Oxford Cryosystems Cryostream cooling apparatus. The intensities were integrated using SAINT+. Corrections for Lorentz and polarization effects were applied. Absorption corrections were applied by using the multiscan program SADABS.13 The structure was solved by direct method, and all non-hydrogen atoms were refined anisotropically by least-squares method on F2 using the SHELXTL program.14 The lattice guest molecules were disordered and could not be modeled properly; thus, program SQUEEZE15 was used to calculate the solvent disorder area and remove its contribution to the overall intensity data. Crystal data as well as details of data collection and refinements for compounds 1·13H2O, 2·9MeOH and 2·5n-BuOH at different temperatures are summarized in Tables 1 and 2.

RESULTS AND DISCUSSION Synthesis. Complexes of 1·13H2O and 2·9MeOH are obtained from solvothermal reactions. The ascorbic acid added in the synthesis is used to prevent the oxidation of the Fe(II) ions. We did not add the oxalate ligands to synthesize complex 2·9MeOH, and the bridging oxalate anions should be produced in situ from oxidative decomposition of ascorbic acid in the presence of [Fe/Et3N]-catalyzed.16 When we use the inorganic base K2CO3 in place of organic alkali Et3N, the ascorbic acid does not decompose and 1D {Fe(tz)3}n chains are obtained. Crystals of 2·9MeOH and 2·5n-BuOH are labile and they cannot keep crystallinity in air or in solvent for a long time due to the loss of guest molecules. So it is difficult to investigate the guest-dependent memory effect for them, and we only report the crystal structures and magnetic properties here. Phase purity of the bulk materials of three compounds are characterized by comparison of the experimental powder diffraction (pXRD) patterns with simulated ones (Figure S3, Supporting Information). Crystal Structures. Structure of [Fe2 (H0.67bdt)3]·13H2O (1·13H2O). Complex 1·13H2O crystallizes in the trigonal space group R3̅m. Its asymmetric unit contains two Fe(II) atoms and three bdt ligands (Figure 1a). Both Fe1 and Fe2 are coordinated by six nitrogen atoms from six bdt ligands. The bridging tetrazolates link Fe1 and Fe2 alternately into a 1D coordination chain {Fe(tz)3}n along the c axis (Figure 1b). It exhibits a three-bladed paddlewheel motif between metal sites, previously described for [Fe(Htrz) 3 ](BF 4 ) 2 ·H 2 O, [Mn4(bdt)3(NO3)2(def)6] and [Co2(H0.67bdt)3]·20H2O (Htrz = triazole, def = diethylformamide).8a,12b,c The chain substructure of 1·13H2O and [Co2(H0.67bdt)3]·20H2O are similar, but their extended modes are different. In the case of [Co2(H0.67bdt)3]·20H2O, a given chain is linked to four adjacent chains providing 3D connectivity and rectangular cavities parallel to the a-axis.12c However, in the case of 1484



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Figure 2. (a) The {Fe3(tz)6} unit; (b) the 1D [Fe3(tz)6(ox)]n chain in 2·solvent, Fe1 and Fe2 atoms are shown in yellow and aubergine, respectively, nitrogen in blue and carbon in gray; (c) the 3D MOF structure viewed along the c-axis and (d) the (6,4)-connected topological network. Hydrogen atoms and lattice solvent molecules have been omitted for clarity.

Table 3. Average Fe−N Bond Lengths (Å) for 1·13H2O at Different Temperatures 100 Ka compound 1·13H2O a

Fe1 2.114

150 Ka Fe2 1.952

Fe1 2.168

200 Ka Fe2 1.961

Fe1 2.176

298 Ka Fe2 1.955

Fe1 2.189

Fe2 1.967

Data derived from single crystal X-ray diffraction analyses.

comprises six tetrazolates N atoms from six bdt ligands to form a distorted octahedral [FeN6] coordinate unit, which implies the possibility of showing spin transition property, whereas the terminal Fe(II) ion (Fe2) is coordinated by three bdt ligands, one ox2− ligand, and one aqua ligand to form a [FeN3O3] unit, which is always in the HS state judging from the ligand field (Figure 2a). The only linear trinuclear Fe(II) unit was previously described in complex [Fe(4Ettr)2(H2O)2]3(CF3SO3)6 (Ettr = 4-ethyltriazole).5b Adjacent trinuclear [Fe3(tz)6] units are linked by ox2− bridges into 1D {Fe 3 (tz) 6 (ox)} n chains (Figure 2b). And then the {Fe3(tz)6(ox)}n chains are extended by bdt ligands into an interesting 3D MOF structure with 1D triangular channels along the c-axis (Figure 2c) and 1D square channels along the a-axis (Figure S1, Supporting Information). The total void volume of the channels without the guest molecules, calculated by PLATON, is 56.3% for 2 at 150 K. When the {Fe2(ox)} groups are simplified as one kind of six-connected node, the Fe1 ions are considered as another kind of six-connected node, and the bdt ligands are regarded as the four-connected node. Therefore, the 3D framework of 2·9MeOH can be described as (6,4)-connected topological network as same as that of 1·13H2O with a Schäfli symbol of (46,66,83)(42,63,8) (Figure 2d). Relevant bond distances and distortion parameters for 2·9MeOH are presented in Table 4. The average Fe1−N distances for 2·9MeOH are 2.08 and 2.09 Å at 110 and 150 K, respectively, suggesting the partial HS state. However, the Fe1 centers as the potential SCO active sites do not show obvious spin state transition as the temperature decreases. The unit cell

1·13H2O, a 1D chain is linked to six adjacent chains through the phenyl tether of the bdt ligand forming a 3D MOF structure and triangular channels along the c-axis (Figure 1c). The total void volume of the channels without guest molecules, calculated by PLATON, is 19.0% for 1 at 200 K. When the bdt ligands are simplified as the four-connected nodes, the Fe(II) ions are considered as six-connected nodes. Therefore, the 3D framework of 1 can be described as (6,4)-connected topological network (Figure 2d) with a Schäfli symbol of (46,66,83)(42,63,8) (Figure 1d).17 The crystal structures of compound 1·13H2O at different temperatures were investigated to check its spin states. Upon cooling, it underwent a dramatic color change from lightred to dark-red, suggesting the presence of spin-state change. Relevant bond distances for 1·13H2O at different temperatures are presented in Table 3. The average Fe2−N distances are near 1.96 Å for all temperatures, suggesting Fe2 ions are always in the LS states, whereas obvious changes are observed for the average Fe1−N bond lengths, which decrease from 2.18 Å at 298 K to 2.11 Å at 100 K indicating the incomplete SCO behaviors. As expected, the unit cell volume is decreased upon cooling. Structures of [Fe3(ox)(H0.67bdt)3(H2O)2]·10H2O·9CH3OH (2·9MeOH) and [Fe3(ox)(H0.67bdt)3(H2O)2]·6H2O·5C4H9OH (2·5n-BuOH). Single crystal X-ray diffraction study reveals that 2·9MeOH crystallizes in the monoclinic space group C2/m and no crystallographic phase transition occurs as temperature decreases (see Supporting Information). The asymmetric units consist of two crystallographically independent Fe(II) atoms. The coordination sphere of the central Fe(II) ion (Fe1) 1485



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Fe1−N bond lengths (see Table 2). After that, the χMT value descends more steeply to 2.50 cm3 K mol−1 at 30 K, corresponding to an incomplete gradual SCO behavior. The further decrease observed below 30 K is due to zero-field splitting and antiferromagnetic interaction of the remaining HS Fe1. For 2·9MeOH, the χMT value is 9.07 cm3 K mol−1 at 300 K, which is smaller than the expected value of 10.5 cm3 K mol−1 for three HS Fe(II) ions (green line in Figure 3b). Since two terminals Fe2 ions are always in the HS states, the decreased χMT value should be due to the partial HS state for the central Fe1 ion judging from the bond length analysis. Upon cooling, it decreases gradually to 7.73 cm3 K mol−1 at 150 K, and then further drops to 0.85 cm3 K mol−1 at 2.0 K. The decay of χMT value should be due to the antiferromagnetic Fe···Fe interaction propagating along the 1D chains linked by mixed tetrazolate and ox2− bridges and magnetically anisotropic HS Fe(II) ion. However, we also notice that the decrease of the χMT value is nonmonotonic in the 300−150 K range, which suggests the possibility of coexistence of an inconspicuous SCO process. Unfortunately, we do not have the high temperature crystal data to prove that. The χMT value for 2·5n-BuOH is 8.89 cm3 K mol−1 at 300 K, which is also smaller than the value for three HS Fe(II) ions (blue line in Figure 3b). In contrast to the complicated decrease of 2·9MeOH, the χMT value decreases monotonically to 0.62 cm3 K mol−1 at 2.0 K, which indirectly suggests the presence of inconspicuous SCO behavior in 2·9MeOH. Although both 2·9MeOH and 2·5n-BuOH have SCO active Fe(II) ions, judging from the average Fe1−N distances, however, the spin state changes should be extremely small and the antiferromagnetic properties are dominate for both of them. The slight difference of magnetic properties in 2·9MeOH and 2·5n-BuOH should be due to the solvent effect. The lack of structural details of solvents prevents us from further investigation. Since substructures of 1·13H2O and 2·solvent are different, the SCO active Fe1 ions are surrounded by the LS and HS ions, respectively. Usually, the spin transition process is self-accelerated with increasing concentration of Fe(II) LS centers. This may be responsible for the different magnetic properties of 1·13H2O and 2·solvent.

Table 4. Average Fe−N Bond Lengths (Å) for 2·9MeOH and 2·5n-BuOH at Different Temperatures 110 Ka compounds 2·9MeOH 2·5n-BuOH a

Fe1 2.087 2.091

Fe2 2.164 2.157

150 Ka Fe1 2.091

Fe2 2.150

293 Ka Fe1

Fe2

2.101

2.145

Data derived from single crystal X-ray diffraction analyses.

volume slightly decreases as the temperature increases, implying the possibility of solvent loss. The general framework topology is maintained when interrogated by the solvent 5n-BuOH, whereas obvious color changes are observed. The structure of 2·5n-BuOH is similar to that of 2·9MeOH except that the guest molecules become water and n-butanol. Relevant bond distances and distortion parameters for 2·5n-BuOH are also presented in Table 1. The Fe1−N distances in 2·5n-BuOH are 2.09 and 2.10 Å at 110 and 298 K, respectively, which also do not show any obvious SCO behavior. The unit cell volume is reduced by 1.5% as the temperature is increased from 110 to 298 K, which is probably due to the solvent loss during the latter measurement. Thermogravimetric Analysis. Thermogravimetric (TG) analyses are carried out to examine thermal stabilities for all the compounds. Samples of 1·13H2O, 2·9MeOH, and 2·5n-BuOH are heated in nitrogen from 303 to 1173 K, 973 K, 773 K at a rate of 10 °C min−1, respectively. For 1·13H2O, a rapid weight loss of 23.5% between 303 and 423 K is in accordance with the release of 13 guest water molecules per formula unit (calculated: 23.7%). The compound is stable until 520 K. After that, a big weight loss is observed corresponding to the decomposition of the organic ligands (Figure S2a, Supporting Information). For 2·9MeOH and 2·5n-BuOH, no plateaus can be found, indicating a relatively low thermal stability of the guest-free frameworks. Maybe the removal of two coordinated aqua molecules on two terminal Fe(II) atoms (Fe2) results in the fragility of the framework (Figure S2b,c, Supporting Information). Magnetic Properties. The temperature dependence of magnetic susceptibilities for 1·13H2O, 2·9MeOH, and 2·5nBuOH are shown in Figure 3. The observed χMT of 1·13H2O is 3.41 cm3 K mol−1 at room temperature, which is close to the value (3.5 cm3 K mol−1) for HS Fe(II). The value decreases gradually to 3.18 cm3 K mol−1 as the temperature decreases to 130 K. In this temperature range, the spin transition process is extremely slow, which is consistent with a slight change of the

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CONCLUSION Two 3D porous Fe(II)-bis(tetrazolate) frameworks containing SCO active sites were prepared and their structure−property correlations were investigated. Complexes 1·13H2O and

Figure 3. Temperature dependence of χMT for (a) 1·13H2O (□), (b) 2·9MeOH (○) and 2·5n-BuOH (○). 1486



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2·solvent were constructed from 1D {Fe(tz) 6 } n and {Fe3(tz)6(ox)}n chains, respectively, and then linked through the phenyl tethers of the bdt ligands into 3D microporous frameworks. The {Fe(tz)6}n chain consists of SCO active Fe1 ions and low-spin (LS) Fe2 ions alternately, while the trinuclear unit [Fe3(tz)6(ox)] contains a partial high-spin (HS) Fe1 ion and two terminal HS Fe2 ions. Complex 1·13H2O presents an incomplete gradual SCO behavior as a function of temperature. In contrast, complex 2·solvent primarily shows antiferromagnetic property, whereas the spin state changes for the Fe1 ions are extremely small. Since the SCO active Fe1 ions in 1·13H2O are surrounded by the LS Fe2 ions, the spin transition process may be self-accelerated with increasing concentration of Fe(II) LS centers. These materials are expected to provide investigations of the structure−property correlation of high dimensional MOF materials containing [FeN6] units.

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ASSOCIATED CONTENT

S Supporting Information *

X-ray crystallographic files of 1·13H2O, 2·9MeOH, and 2·5nBuOH (CIF). Picture of 1D square channels along the a-axis in 2·9MeOH. Simulated and experimental pXRD data and thermogravimetric analysis curves of 1·13H2O, 2·9MeOH, and 2·5n-BuOH. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: Int. code +86 20 8411-0966. Fax: +86 20 8411-2245. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the NSFC (Grants 91122032, 50872157, and 21121061) and the National Basic Research Program of China (2012CB821704).

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REFERENCES

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Incomplete Spin Crossover versus Antiferromagnetic Behavior

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