CRYSTAL GROWTH & DESIGN 2006 VOL. 6, NO. 3 632-635
Articles Synthesis and Characterization of New Open-Framework Iron(II) Phosphate with 1D Tube and Double Layer Structure, NaFe2(PO4)(HPO4) Zhi-Feng Zhao,† Bai-Bin Zhou,*,† Zhan-Hua Su,† Xu Zhang,† and Guang-Hua Li‡ Department of Chemistry, Harbin Normal UniVersity, Harbin 150080, China, and State Key Laboratory of Inorganic Synthesis and PreparatiVe Chemistry, College of Chemistry, Jilin UniVersity, Changchun 130023, China ReceiVed April 12, 2005; ReVised Manuscript ReceiVed December 6, 2005
ABSTRACT: A novel two-dimensional layered iron(II) phosphate, NaFeII2(PO4)(HPO4), has been synthesized under mild hydrothermal conditions. Its structure was determined by single-crystal X-ray diffraction and further characterized by FTIR, elemental analysis, inductively coupled plasma (ICP) analysis, powder X-ray diffraction, and magnetic susceptibility measurements. Its anionic network is based on strictly alternating FeIIO4 tetrahedral units and P-centered units including PO4 and PO3(OH) tetrahedra linked through their vertices to form a double layered structure that contains columns of double six-membered rings and 1D tubes by four-membered rings sharing faces. The sodium atoms reside in the interlayer region. The title compound crystallizes in the triclinic system, space group P1h, with the following cell parameters: a ) 5.1200(10) Å; b ) 8.6232(17) Å; c ) 8.7958(18) Å; R ) 96.93(3)°; β ) 100.45(3)°; γ ) 105.75(3)°; V ) 361.58(12) Å3; Z ) 2; Dc ) 2.991 Mg/m3. Introduction Over the past few decades, the research in the area of microporous materials has been very intense due to their rich structural chemistry and the potential applications in the areas of catalysis, separation, and adsorption.1 Following the discovery of crystalline aluminophosphate molecular sieves in 1982,2 a large number of open-framework metal phosphates have been synthesized under hydrothermal conditions.3 Much interest has been focused on open-framework metal phosphates because of their compositional diversity and novel architecture.4,5 these compounds possess different inorganic partial structures, such as 0D clusters,6 1D chains,7 2D layers,8,9 and 3D open frameworks10 and several metal phosphates possessing helical channels11-13 and extra-large micropores.14,15 One of the strategies used for the design and synthesis of these materials is the presence of organic amines or metal complexes as structuredirecting agents. Recently, open-framework inorganic material has experienced a dramatic increase. The iron phosphates have opened the way to a new class of open-framework solids that combine the wellknown sieving properties and interesting magnetic properties.4,16 In most open-framework iron phosphates, the empty space is filled by organic molecules, water, or ammonia,17 such as [C4H12N2]1.5[Fe2(OH)(H2PO4)(HPO4)2(PO4)]‚0.5H2O18 and * To whom correspondence should be addressed. Tel: +86-45188060653. E-mail address:
[email protected]. † Harbin Normal University ‡ Jilin University
Fe(NH3)2PO4.17 In the title compound, however, sodium atoms reside in the interlayer region. This paper reports 2D layered open-framework iron(II) phosphate for the first time. In this paper, we describe the synthesis, crystal structure, and magnetic properties of NaFe2(PO4)(HPO4), denoted as 1. Based on our previous work, a novel iron(II) phosphate, NaFe2(PO4)(HPO4), with a 2D corrugated layered structure has been hydrothermally synthesized. The distinctive feature of 1 with the presence of FeII tetrahedra is the formation of 1D tubes by four-membered rings and a double layered structure by sixmembered rings. Experimental Section Materials and Methods. All reagents were purchased commercially and used without further purification. Inductively coupled plasma (ICP) analysis was carried out on a Perkin-Elmer Optima 3300 DV spectrometer. The infrared spectrum was obtained on a Nicolet Impact 410 FTIR spectrometer in the 400-4000 cm-1 region with pressed KBr pellets. Powder X-ray diffraction (XRD) data were collected on a Rigaku D/max III diffractometer with Cu KR radiation (λ ) 1.5418 Å). The magnetic property was measured on a Quantum Design SQUID MPMS-XL5 magnetometer in a field of 10 000 Oe. Magnetic susceptibility dependences of temperature were measured in the range 300-2 K. Synthesis of NaFe2(PO4)(HPO4) 1. In a typical synthesis for 1, a mixture of FeCl2‚4H2O (0.638 g), La(NO3)3‚6H2O (1.387 g), NaMoO4‚ 2H2O (1.21 g), H3PO4 (0.75 mL, 85 wt %), C6H4(OH)COOH (0.25 g), 4,4′-bipyridine (0.075 g), ethylenediamine (0.5 mL), and H2O (25 mL) in a molar ratio of 1.0:1.00:1.56:3.80:0.57:0.15:2.34:433.59 was stirred under ambient conditions until it was homogeneous. The resulting gel
10.1021/cg050142a CCC: $33.50 © 2006 American Chemical Society Published on Web 01/26/2006
Open-Framework Iron(II) Phosphate, NaFe2(PO4)(HPO4)
Crystal Growth & Design, Vol. 6, No. 3, 2006 633 Table 1. Crystal Data and Structure Refinement for 1 empirical formula formula weight temp, K wavelength, Å crystal system space group a, Å b, Å c, Å R, deg β, deg γ, deg V, Å3 Z Dc, Mg/m3 µ (Mo KR), mm-1 F(000) θ range (deg) limiting indices
HFe2NaO8P2 325.64 293(2) 0.710 73 triclinic P1h 5.1200(10) 8.6232(17) 8.7958(18) 96.93(3) 100.45(3) 105.75(3) 361.58(12) 2 2.991 4.523 316 4.23-27.45 -6 e h e 6 -11 e k e 11 -11 e l e 11 3512 1599 [R(int) ) 0.0176] 1599/0/119 1.107 0.0365, 0.0950
reflns collected independent reflns
Figure 1. Simulated and experimental powder X-ray diffraction patterns of 1. with a pH of 6.2 was loaded into a Teflon-lined steel autoclave and heated at 160 °C for 6 days under static conditions. The solid product containing colorless blocklike single crystals was collected by filtration, washed thoroughly with distilled water, and dried at room temperature (65% yield based on Fe). It is noteworthy that organic entities and metal salts were not involved in the coordination in 1. However, many controlled experiments indicate that the above proportion is optimum for the formation of the product without organic entities and metal salts; the directed reaction of inorganic parts under the same conditions do not produce the anticipated product, which suggests that organic entities and metal salts play an important template role in the formation of 1. In addition, the different acidity/basicity value of the reaction under hydrothermal condition might influence the transformation of different oxidation states of transition metal elements. In our case, the pH value of the reaction system was the key factor for the crystallization of products, so acid or amine is added to adjust the pH value of the reaction system. The purity of the product was checked by comparing its experimental and simulated XRD patterns. The diffraction peaks on both patterns corresponded well in position (Figure 1), indicating the phase purity of the product. The difference in reflection intensities between the simulated and experimental patterns was believed to be caused by preferred orientation of the powder sample during collection of the experimental XRD data. The ICP and elemental analysis results were also consistent with the theoretical values. Calculated from the compound: Fe, 34.30; P, 19.02; Na, 7.06; H, 0.31%. Found: Fe, 34.12; P, 18.98; Na, 7.01; H, 0.35%. IR (KBr, cm-1 ) for 1: 3441s, 1163s, 1057s, 949s, 793s, 759s, 595w, 499w. X-ray Crystallography. A suitable single crystal with dimensions of 0.27 × 0.19 × 0.12 mm3 for compound 1 was carefully selected for single-crystal X-ray diffraction analysis. Data collections were performed on a Rigaku RAXIS-RAPID equipped with a narrow-focus, 5.4 kW sealed tube X-ray source (graphite-monochromated Mo KR radiation, λ) 0.71073 Å). The data were collected at a temperature of 20 ( 2 °C. The data processing was accomplished with the PROCESSAUTO processing program. The structure was solved by direct methods and refined on F2 by full-matrix least-squares methods using the SHELXTL97 program package.19 The Fe and P atoms were easily located, and O and H atoms in the P-OH groups in 1 were located by Fourier maps. All non-hydrogen atoms were refined with anisotropic thermal parameters. Experimental details for the structural determination are presented in Table 1. Final atomic positional and thermal parameters are given in Table 2, and selected bond distances and bond angles are summarized in Table 3.
Result and Discussion Description of Structure. Structure of NaFeII2(PO4)(HPO4), 1. The compound 1 was characterized with a new
data/restraint/params GOF on F2 final R1, wR2 [I > 2σ(I)]
Table 2. Atomic Coordinates (×104) and Equivalent Isotropic Displacement Parameters (Å2 × 103) for 1 Fe(1) Fe(2) P(1) P(2) Na(1) O(1) O(2) O(3) O(4) O(5) O(6) O(7) O(8)
x
y
z
U(eq)a
2213(1) -3305(1) -1609(2) 912(2) 14092(5) 1055(7) 2723(7) 5864(7) -573(7) -1405(8) -1890(8) -2749(8) -2058(8)
1120(1) 3826(1) 2443(2) 2503(1) 1865(3) 1957(5) 2595(4) 953(4) -887(4) 3796(4) 2738(5) 6155(4) 3152(5)
2596(1) 1069(1) 4185(1) -603(1) -3114(3) 4456(4) 1065(4) 3487(4) 1640(4) 3201(4) -497(4) 1272(4) 5824(4)
8(1) 7(1) 17(1) 17(1) 28(1) 24(1) 22(1) 24(1) 25(1) 25(1) 26(1) 24(1) 24(1)
a U(eq) is defined as one-third of the trace of the orthogonalized U ij tensor.
Figure 2. ORTEP plot of 1 showing the labeling scheme (50% thermal ellipsoids).
layered structure based on sheets of FeO4 and PO4 tetrahedra fused together via Fe-O-P and Fe-O-Fe bonds. Each asymmetric unit of 1 contains 13 non-hydrogen atoms, as seen in Figure 2, two Fe and two P atoms being crystallographically distinct. The iron(II) atom is tetrahedrally coordinated and shares four oxygen atoms with adjacent P atoms. The Fe-O bond
634 Crystal Growth & Design, Vol. 6, No. 3, 2006
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Table 3. Select Bond Lengths (Å) and Angles (deg) for 1a Fe(1)-O(4) Fe(1)-O(3) Fe(1)-O(1) Fe(1)-O(2) Fe(2)-O(6) Fe(2)-O(7) Fe(2)-O(5) Fe(2)-O(2)a P(1)-O(1) P(1)-O(3)a P(1)-O(5) P(1)-O(8) P(2)-O(4)b P(2)-O(6) P(2)-O(7)c P(2)-O(2) a
1.900(4) 1.942(4) 1.962(4) 1.965(4) 1.929(4) 1.932(4) 1.956(4) 2.022(4) 1.520(4) 1.524(4) 1.527(4) 1.578(4) 1.520(4) 1.520(4) 1.531(4) 1.567(4)
O(4)-Fe(1)-O(3) O(4)-Fe(1)-O(1) O(3)-Fe(1)-O(1) O(4)-Fe(1)-O(2) O(3)-Fe(1)-O(2) O(1)-Fe(1)-O(2) O(6)-Fe(2)-O(7) O(6)-Fe(2)-O(5) O(7)-Fe(2)-O(5) O(6)-Fe(2)-O(2)a O(7)-Fe(2)-O(2)a O(5)-Fe(2)-O(2)a O(1)-P(1)-O(3)a O(1)-P(1)-O(5) O(3)a-P(1)-O(5) O(1)-P(1)-O(8)
115.97(16) 106.04(16) 102.60(16) 110.17(16) 106.91(15) 115.24(15) 119.67(16) 111.73(16) 98.37(16) 112.08(16) 111.48(15) 101.08(15) 111.0(2) 111.3(2) 112.6(2) 108.8(2)
O(3)a-P(1)-O(8) O(5)-P(1)-O(8) O(4)b-P(2)-O(6) O(4)b-P(2)-O(7)c O(6)-P(2)-O(7)c O(4)b-P(2)-O(2) O(6)-P(2)-O(2) O(7)c-P(2)-O(2) P(1)-O(1)-Fe(1) P(2)-O(2)-Fe(1) P(1)j-O(3)-Fe(1) P(2)b-O(4)-Fe(1) P(2)c-O(7)-Fe(2) P(2)-O(6)-Fe(2) P(1)-O(5)-Fe(2) P(2)-O(2)-Fe(2)j
105.9(2) 107.0(2) 111.5(2) 106.6(2) 113.8(2) 109.6(2) 111.4(2) 103.5(2) 117.4(2) 130.8(2) 123.0(2) 140.0(2) 132.6(2) 135.4(2) 132.3(2) 107.16(19)
Symmetry transformations used to generate equivalent atoms were as follows: (a) x - 1, y, z; (b) -x, -y, -z; (c) -x, -y + 1, -z.
Figure 3. Polyhedral view of the cage. The building unit of the structure, FeO4, is colored black; PO4 is colored medium gray. Figure 5. View of the structure of 1 along the c-axis.
Figure 4. Structure showing the 1D tube formed by face-sharing cages.
distances are in the range of 1.900(4)-2.022(4) Å, and O-Fe-O angles lie between 98.37(16)° and 119.67(16)°. Each P atom is tetrahedrally coordinated by oxygen atoms. P(1) makes three bonds to nearby Fe atoms via bridging oxygen (P-O) and possesses one terminal P-OH bond [d(P-OH)av ) 1.578(4) (Å)]. P(2) shares four oxygen atoms with adjacent FeII atoms. The P-O bond lengths are in the range of 1.520(4)-1.578(4) Å. O-P-O bond angles are in the range of 103.5(2)°113.8(2)°. Assuming the usual valence of P, O, and H to be +5, -2, and +1, respectively, and that of Fe to be +2, the network stoichiometry of Fe2(PO4)(HPO4) creates a net charge of -1, and one sodium atom per formula unit balances this negative charge. The framework structure of 1 is based on a network of strictly alternating Fe-centered units (FeIIO4) and P-centered units (PO4) in which all the vertices are shared excepted for the terminal H atoms in HPO4 groups. The vertex linkages of FeO4 and PO4 tetrahedra form the building unit, a cage that can been seen as the building up of two three-membered rings, four fourmembered rings, and two six-membered rings (Figure 3). This 3.4.6-net structure is found for the first time in iron(II) phosphates. However, interestingly, this 3.4.6-net has been
Figure 6. Packing of the layer along the [100] direction. FeO4 is colored black; PO4 is colored medium gray.
reported for the 2D 3.4.6-net of layered zinc phosphates, such as [C6N2H16]3.5[Zn14(PO4)7(HPO4)7],20 upon replacing the Fe atoms with Zn atoms and the Na atom with the organic amine molecule. Two six-membered rings interconnect with each other via oxygen atoms forming a puckered double layer structure. The cages are connected by sharing faces via four-membered rings to form 1D tubes (Figure 4), while the 1D tubes are linked through oxygen atoms forming anionic layers. The anionic part in the asymmetric unit can be considered as secondary building units, which are connected to each other via vertex oxygens forming a layer parallel to the ab plane (Figure 5). The layer contains columns of double six-membered rings along the [001] direction. The layers are stacked in an -AAA- sequence along the [100] direction forming the two-dimensional corrugated layer structure (Figure 6). It is noticed that the P-OH groups
Open-Framework Iron(II) Phosphate, NaFe2(PO4)(HPO4)
Crystal Growth & Design, Vol. 6, No. 3, 2006 635
Table 4. Hydrogen Bond Information for 1a DsDH‚‚‚A
d(DsDH) (Å)
d(H‚‚‚A) (Å)
d(D‚‚‚A) (Å)
∠(DHA) (deg)
O(8)-H(8)‚‚‚O(7)n O(8)-H(8)‚‚‚O(4)o
0.82 0.82
2.60 2.66
3.081(5) 3.463(5)
118.5 167.5
a Symmetry transformations used to generate equivalent atoms were as follows: (n) -x, -y + 1, -z + 1; (o) -x, -y, -z + 1.
Conclusions A new two-dimensional layered iron(II) phosphate, NaFe2(PO4) (HPO4), has been obtained from hydrothermal systems. Structural analyses indicate that 1 is built up from strict alternation of FeO4 tetrahedra and PO4 tetrahedra by sharing vertex oxygen atoms forming a double layered structure. There are three noticeable characteristics for 1: The first is that it possesses 1D tubes formed by four-membered rings sharing faces. The second is that it contains a double layer structure formed by two six-membered rings via oxygen atom linkages. The last is an iron(II) atom with four coordination forming FeO4 tetrahedral. The successful synthesis of 1 opens the field of synthetic chemistry in iron(II) phosphate systems. Acknowledgment. This work is supported by the National Natural Science Foundation of China (Grant No. 29671009). Supporting Information Available: Additional figure and crystallographic information files. This material is available free of charge via the Internet at http://pubs.acs.org.
References
Figure 7. Thermal evolution of the χmT for 1 from 2 to 300 K at 10 000 Oe. Inset: χm-1 vs temperature above 110 K.
exclusively protrude into the interlayer region and interact with adjacent layers through H-bonds. The key of charge-balancing requires the presence of protons associated with the P-O bonds. The hydrogen bonds of 1 are summarized in Table 4. Sodium atoms exist in the interlayer region and balance the net charge. Magnetic Properties. The temperature dependence of the magnetic susceptibilities was measured in the temperature range 300-2 K with a magnetic field of 10 000 Oe. The χmT vs T curves are shown in Figure 7. When compound was cooled from room temperature, the value of χmT steadily decreased, which indicates the existence of antiferromagnetic interactions between the FeII ions. Between 300 and 130 K (see inset in Figure 7), the measured data are fitted using the Curie-Weiss equation, χm ) C/(T - θ), where C ) 11.65 emu K mol-1 and θ ) -45.7 K. This fact further confirms the existence of antiferromagnetic interactions. The effective magnetic moment calculated from the formula µeff ) 2.828(χmT)1/2 at 300 K is 6.21µB . This value is higher than the theoretical one for a spin-only FeII ion (4.90µB) and can be expected due to the existence of a spin-orbital coupling contribution to the moment.
(1) Davis, M. E.; Lobo, R. F. Chem. Mater. 1992, 4, 756. (2) Wilson, S. T.; Lok, B. M.; Messina, C. A.; Cannan, T. R.; Flanigen, E. M. J. Am. Chem. Soc. 1982, 104, 1146. (3) Yu, J.; Xu, R. Acc. Chem. Res. 2003, 36, 481. (4) Cheetham, A. K.; Fe´rey, G.; Loiseau, T. Angew. Chem., Int. Ed. Engl. 1999, 38, 3268. (5) Rao, C. N. R.; Natarajan, S.; Choudhury, A.; Neeraj, S.; Ayi, A. A. Acc. Chem. Res. 2001, 34, 80. (6) Lin, Z. E.; Zhang, J.; Zheng, S. T.; Wei, Q. H.; Yang, G. Y. Solid State Sci. 2003, 5, 1435. (7) Fernandez, S.; Mesa, J. L.; Pizarro, J. L.; Lezama, L.; Arriortua, M. I.; Rojo, T. Chem. Mater. 2003, 15, 1204. (8) Wang, Y.; Yu, J.; Li, Y.; Du, Y.; Xu, R.; Ye, L. J. Solid State Chem. 2003, 170, 303. (9) Mao, J. G.; Wang, Z. K.; Clearfield, A. Inorg. Chem. 2002, 41, 6106. (10) Lin, Z. E.; Zhang, J.; Zheng S. T.; Yang, G. Y. Microporous Mesoporous Mater. 2004, 68, 65. (11) Neeraj, S.; Natarajan, S.; Rao, C. N. Chem. Commun. 1999, 165. (12) Lin, Z. E.; Yao, Y. W.; Zhang, J.; Yang, G. Y. J. Chem. Soc., Dalton Trans. 2002, 4527. (13) Wang, Y.; Yu, J.; Guo, M.; Xu, R. Angew. Chem., Int. Ed. 2003, 42, 4089. (14) Yang, G. Y.; Sevov, S. C. J. Am. Chem. Soc. 1999, 121, 8389. (15) Rodgers, J. A.; Harrison, W. T. A. J. Mater. Chem. 2000, 10, 2853. (16) Riou-Cavellec, M.; Riou, D.; Fe´rey, G. Inorg. Chim. Acta, 1999, 291, 317. (17) Gon˜i, A.; Lezama, L.; Espina, A.; Trobajo, C.; Garcı´a, J. R.; Rojo, T. J. Mater. Chem. 2001, 11, 2315. (18) Zima, V.; Lii K. H. J. Chem. Soc., Dalton Trans. 1998, 4109. (19) Sheldrick, G. M. SHELXL Program, version 5.1; Siemens Industrial Automation, Inc.: Madison, WI, 1997. (20) Xing, Y.; Li, G. H.; Meng, H.; Shi, Z.; Liu, Y. L.; Wei, X. H.; Yang, Y. L.; Pang, W. Q. Inorg. Chem. Commun. 2004, 7, 475.
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