Structures and Magnetic Properties of a Series of Metal

Crystal Growth & Design , 2006, 6 (6), pp 1445–1452 ... Publication Date (Web): May 12, 2006. Copyright ... Cite this:Crystal Growth & Design 6, 6, ...
1 downloads 0 Views 797KB Size
Download PDF
Structures and Magnetic Properties of a Series of Metal Phosphonoacetates Synthesized from in Situ Hydrolysis of Triethyl Phosphonoacetate Juan-Juan Hou and Xian-Ming Zhang*

CRYSTAL GROWTH & DESIGN 2006 VOL. 6, NO. 6 1445-1452

School of Chemistry & Material Science, Shanxi Normal UniVersity, Linfen, Shanxi 041004, China ReceiVed February 15, 2006; ReVised Manuscript ReceiVed April 10, 2006

ABSTRACT: Seven new metal phosphonoacetates, namely, [Zn7(OH)2(ppat)4(H2O)2] (1), H3O[Zn(ppat)] (2), [Zn3(4,4′-bpy)(ppat)2] (3), H2dmpz0.5[Zn(ppat)]‚H2O (4), (H3O)2[Co3(OH)2(ppat)2] (5), H24,4′-bpy[VIV2O2(ppat)2] (6), and [FeIII(ppat)(H2O)] (7) (H3ppat ) phosphonoacetic acid, 4,4′-bpy ) 4,4′-bipyridine, dmpz ) N,N′-dimethylpiperazine) were hydrothermally synthesized by the in situ hydrolysis of triethyl phosphonoacetate route. X-ray crystallography reveals that 1 shows a two-dimensional layered structure containing octahedral, tetrahedral, and trigonal bipyramidal Zn sites and an unprecedented inorganic Zn-O ribbon; 2 has a threedimensional framework with one-dimensional dumbbell-shaped channels encapsulating protonated water molecules; 3 is a neutral three-dimensional framework constructed by [Zn(4,4′-bpy)]n2n+ chains and [Zn(ppat)]nn- layers, two types of structural motifs; 4 shows a three-dimensional hydrogen bond network constructed by [Zn(ppat)]- anionic layers and N,N′-dimethylpiperazinium cations; 5 is a layered structure containing inorganic Co-O chains consisting of edge-shared CoO6 octahedra; 6 has a 3D hydrogen bond array constructed from [V2O2(ppat)]n2n- layers and doubly protonated 4,4′-bpy cations; 7 crystallizes in a chiral space group and has a 3D four-connected framework with diamond topology. Magnetic measurements reveal antiferromagnetic behavior for 5, paramagnetic behavior for 6, and canted antiferromagnetic behavior for 7. Introduction The desire to develop new materials in ion exchange, sorption, catalysis, molecular magnetism, sensors, and nonlinear optics has led to increasing interest in the synthesis of metal phosphonate materials over the recent years.1-7 It could be regarded that metal organophosphonate open framework materials are located between zeolite-like and metal-organic framework materials.8-13 The nature of the organic phosphonic acid in these metal phosphonates can be designed to confer specific properties to this class of solids.14-18 The dimensionality of metal phosphonates could be directly influenced by a Z functional end and an R group of O3P-R-Z.19-27 Some progress has been made in the construction of microporous metal phosphonate materials as exemplified by Maeda’s recent review.1 However, one problem is that many metal phosphonates from traditional methods are often formed too rapidly to allow growth of crystals sufficiently large for single-crystal structural determination.28-34 On the other hand, hydrothermal in situ ligand synthesis has been rapidly developed over the past several years due to a simple operating step, environmental friendliness, and easiness to grow large single crystals.35 Actually, hydrothermal in situ ligand synthesis has become a forceful approach in crystal engineering of coordination complexes, especially for those not accessible from a direct reaction of metal ions and ligands. Up to now, the bifunctional biphosphonates have been used to synthesize many 2D or 3D hybrid materials based on various metal cations, but bifunctional phosphonate-carboxylates are relatively less used.23,24,27 As for metal phosphonoacetates, only several examples have been structurally described in the literature,8,22,36,37 and all the metal phosphonoacetates are prepared by direct reaction of phosphonoacetic acid and metal salts. Recently, we reported microporous Na[Zn(O3PC2H4CO2)]‚ H2O 38 and [Cd(phen)(HO3PC2H4CO2)]‚4H2O 39 by the hydrothermal in situ hydrolysis of trialky phosphonopropionate route. * To whom correspondence should be addressed. Tel and Fax: 86-3572051402. E-mail: [email protected].

In this article, we present seven new metal (M ) Zn, Co, V, and Fe) phosphonoacetates, [Zn7(OH)2(ppat)4(H2O)2] (1), H3O[Zn(ppat)] (2), [Zn3(4,4′-bpy)(ppat)2] (3), H2dmpz0.5[Zn(ppat)]‚ H2O (4), (H3O)2[Co3(OH)2(ppat)2] (5), H24,4′-bpy[VIV2O2(ppat)2] (6), and [FeIII(ppat)(H2O)] (7) (H3ppat ) phosphonoacetic acid, 4,4′-bpy ) 4,4′-bipyridine, dmpz ) N,N′-dimethylpiperazine), which were synthesized by the hydrothermal in situ hydrolysis of triethyl phosphonoacetate route. Experimental Section General. All chemicals are commercially purchased and used without purification: zinc sulfate, cadmium sulfate, cobalt sulfate, vanadyl sulfate, hydrofluoric acid, and acetonitrile were purchased from Tianjin Chemical Ltd., while triethyl phosphonoacetate, pyrazine, N,N′dimethylpiperazine, N-ethylpiperazine, and 4,4′-bipyridine were obtained from ACROS. All syntheses were carried out in a 15 mL Teflonlined reactor under autogenous pressure with a filling capacity of 50%. The CHN microanalysis was performed on a Perkin-Elmer 240 elemental analyzer. The FT-IR spectra were recorded from KBr pellets in the range 4000-400 cm-1 on a Nicolet 5DX spectrometer. Thermal gravimetric analyses (TGA) were performed under static air atmosphere from 30 to 800 °C using a Perkin-Elmer 7 thermogravimetric analyzer with a heating rate of 10 °C min-1. The magnetic measurements were carried out with Quantum Design SQUID MPMS XL-7 instruments. Preparations. [Zn7(OH)2(ppat)4(H2O)2] (1). A mixture of ZnSO4‚ 7H2O (0.172 g, 0.6 mmol), triethyl phosphonoacetate (0.069 g, 0.3 mmol), N-ethylpiperazine (0.141 g, 1.2 mmol), and H2O (5 mL) in the molar ratio of 2:1:4:460 was stirred, dropped by hydrofluoric acid (35%) to pH ≈ 5, sealed into a Teflon-lined reactor, and heated to 170 °C for 120 h. Colorless needle crystals of 1 suitable for X-ray diffraction were isolated in 45% yield. The final pH value of 7 was recorded. Anal. calcd for C8H14O24P4Zn7: C, 8.93; H, 1.31. Found: C, 8.85; H, 1.42. IR (KBr, cm-1): 3410(sb), 3280(sb), 3006(m), 2925(w), 2842(w), 1656(s), 1588(s), 1438(s), 1404(s), 1334(s), 1219(s), 1178(s), 1123(s), 1061(s), 965(s), 814(m), 643(s), 574(s), 506(m), 472(m). H3O[Zn(ppat)] (2). The reaction of ZnSO4‚7H2O (0.286 g, 1 mmol), triethyl phosphonoacetate (0.122 g, 0.5 mmol), pyrazine (0.026 g, 0.3 mmol), acetonitrile (2 mL), and H2O (5 mL) in the mole ratio 10:5: 3:380:2800 was stirred, dropped by hydrofluoric acid (35%) to pH ≈ 5, sealed into a Teflon-lined reactor, and heated to 170 °C for 120 h. Colorless stick crystals of 2 suitable for X-ray diffraction were isolated

10.1021/cg0600750 CCC: $33.50 © 2006 American Chemical Society Published on Web 05/12/2006

1446 Crystal Growth & Design, Vol. 6, No. 6, 2006 in 65% yield. Anal. calcd for C2H5O6PZn: C, 10.85; H, 2.28. Found: C, 10.77; H, 2.36. IR (KBr, cm-1): 3430(sb), 3143(sb), 1594(m), 1396(s), 1219(w), 1129(m), 1068(m), 992(m), 938(m), 828(w), 740(w), 650(m), 568(m), 479(m). [Zn3(4,4′-bpy)(ppat)2] (3). A mixture of ZnSO4‚7H2O (0.230 g, 0.8 mmol), triethyl phosphonoacetate (0.099 g, 0.4 mmol), 4,4′-bipyridine (0.062 g, 0.4 mmol), and H2O (7 mL) in the molar ratio of 2:1:1:970 was stirred, dropped by hydrofluoric acid (35%) to pH ≈ 4, sealed into a Teflon-lined reactor, and heated to 180 °C for 120 h. Colorless block crystals of 3 suitable for X-ray diffraction were isolated in 40% yield. The final pH value of 3 was recorded. Anal. calcd for C14H12N2O10P2Zn3: C, 26.85; H, 1.93; N, 4.47. Found: C, 26.77; H, 2.01; N, 4.39. IR (KBr, cm-1): 3109(w), 2914(w), 1617(s), 1554(s), 1423(s), 1388(s), 1228(s), 1172(s), 1082(s), 1006(s), 819(s), 748(m), 652(s), 590(s), 492(m). H2dmpz0.5[Zn(ppat)]‚H2O (4). A mixture of Zn(OAc)2‚2H2O (0.175 g, 0.8 mmol), triethyl phosphonoacetate (0.134 g, 0.6 mmol), N,N′dimethylpiperazine (0.116 g, 1 mmol), and H2O (8 mL) was stirred, dropped by hydrofluoric acid (35%) to pH ≈ 5, transferred into a 15 mL Teflon-lined stainless steel reactor, and heated at 170 °C for 120 h. After the mixture cooled to room temperature, colorless block crystals of 4 (52% yield) were recovered. Anal. calcd for C5H12NO6PZn: C, 21.56; H, 4.34; N, 5.03. Found: C, 21.50; H, 4.46; N, 4.93. IR (KBr, cm-1): 3428(bs), 2921w, 2887(w), 1587(s), 1426(s), 1089(m), 1012(m), 986(m), 532(m). (H3O)2[Co3(OH)2(ppat)2] (5). A solution of CoSO4‚7H2O (0.112 g, 0.40 mmol), triethyl phosphonoacetate (0.069 g, 0.3 mmol), 4,4′bipyridine (4,4′-bpy) (0.047 g, 0.30 mmol), and H2O (6 mL) in the molar ratio 4:3:3:3330 was stirred, dropped by hydrofluoric acid (35%) to pH ≈ 2, sealed, and heated to 170 °C for 225 h. Pink crystals of 5 were isolated in 30% yield. Anal. calcd for C4H12Co3O14P2: C, 9.01; H, 2.3. Found: C, 9.19; H, 2.31. IR (KBr, cm-1): 3437(bs), 3139(bs), 2925w, 1633(m), 1540(m), 1397(s), 1202(w), 1100(m), 998(m), 660(m), 537(m). H24,4′-bpy[VIV2O2(ppat)2] (6). A mixture of VOSO4 (0.147 g, 0.9 mmol), triethyl phosphonoacetate (0.143 g, 0.6 mmol), 4,4′-bipyridine (0.47 g, 0.3 mmol), and H2O (7 mL) in the molar ratio 3:2:1:1300 was stirred, dropped by hydrofluoric acid (35%) to pH ≈ 3, sealed, and heated to 170 °C for 96 h, yielding yellow-green crystals of 6 in 65% that were suitable for X-ray diffraction. Anal. calcd for C14H14N2V2O12P2: C, 29.70; H, 2.49; N, 4.95. Found: C, 29.51; H, 2.27; N, 4.50. IR (KBr, cm-1): 3137(sb), 2997(m), 1623(s), 1492(s) 1402(s), 1191∼943(sb), 860(s), 819(s), 756(m), 715(w), 665(s), 526(s). [FeIII(H2O)(ppat)] (7). The reaction of FeSO4‚7H2O (0.141 g, 0.5 mmol), triethyl phosphonoacetate (0.120 g, 0.5 mmol), and H2O (6 mL) in the molar ratio 5:5:3330 was stirred and dropped by hydrofluoric acid (35%) to pH ≈ 2 before heating to 170 °C for 120 h. White block crystals of 7 were isolated in 40% yield. Anal. calcd for C2H4O6PFe: C, 11.39; H, 1.91. Found: C, 11.32; H, 1.89. IR (KBr, cm-1): 34113117(sb), 2440(w), 1633(m), 1505(m), 1397(s), 1244(w), 1158(s), 1070(s), 950(m), 855(m), 750(w), 529(s). X-ray Crystallography. Crystallographic data were collected using a Bruker SMART APEX CCD area detector diffractometer at 293(2) K using Mo KR radiation (λ ) 0.710 73 Å) by ω and φ scan mode. The program SAINT was used for integration of the diffraction profiles. All the structures were solved by direct methods using the SHELXS program of the SHELXTL package and refined by full-matrix leastsquares methods with SHELXL-97.40 All non-hydrogen atoms were refined with anisotropic thermal parameters. All hydrogen atoms of organic ligands were generated theoretically onto the specific carbon atoms and refined isotropically with fixed thermal factors. Compounds 2, 3, 6, and 7 crystallize in noncentrosymmetric space groups, and the correctness for these compounds has been carefully checked by PLATON.41 Further details for structural analysis are summarized in Table 1.

Results and Discussion Synthesis Chemistry. Different from traditional methods employed in the syntheses of metal phosphonates, compouds 1-7 are synthesized by hydrothermal in situ ligand reaction. The triethyl phosphonoacetate as the source of phosphonoacetate acid is important for single crystal formation of 1-7. The synthesis method in this work has two benefits: (1) the use of

Hou and Zhang Table 1. Crystal Data and Structure Refinement Parameters for 1-7 compound formula FW crystal system space group a (Å) b (Å) c (Å) R (deg) β (deg) γ (deg) V (Å3) Z Fcalc (g cm-3) µ (mm-1) F(000) size (mm3) θ (deg) reflns Tmax/Tmin data/ params S R1a wR2b ∆Fmax/ ∆Fmin

1

2

3

4

C8H14O24P4Zn7 C2H5O6PZn 1075.66 221.40 triclinic orthorhombic

C14H12N2O10P2Zn3 C5H12NO6PZn 626.31 278.50 monoclinic monoclinic

P1h

Pna21

Cc

P21/c

7.6064(14) 7.7529(14) 10.2484(18) 85.574(3) 80.933(3) 77.240(3) 581.51(18) 1 3.072

9.5524(9) 12.5921(12) 5.1876(5) 90 90 90 623.99(10) 4 2.357

21.790(3) 5.6611(9) 16.867(3) 90 112.951(2) 90 1915.9(5) 4 2.171

10.0001(8) 8.3697(7) 11.3991(9) 90 95.289(2) 90 950.02(13) 4 1.947

7.488 524 0.35 × 0.05 × 0.04 2.01-28.42 4478/2608 0.7538/0.1792 2608/0/196

4.161 440 0.35 × 0.10 × 0.08 2.68-28.25 2961/1329 0.7319/0.3237 1329/1/103

3.953 1240 0.29 × 0.27 × 0.10 2.62-28.48 6391/3911 0.6933/0.3936 3911/2/281

2.758 568 0.35 × 0.27 × 0.22 2.05-27.00 4421/2035 0.5821/0.4453 2035/0/136

1.008 0.0480, 0.1049 0.0706,0.1153 1.049/-0.961

1.049 0.0245, 0.0660 0.0249, 0.0663 0.481/-0.455

1.039 0.0271, 0.0680 0.0280, 0.0684 1.255/-0.357

1.032 0.0214, 0.0602 0.0234, 0.0608 0.354/-0.353

compound

5

6

7

formula FW crystal system space group a (Å) b (Å) c (Å) R (deg) β (deg) γ (deg) V (Å3) Z Fcalc (g cm-3) µ (mm-1) F(000) size (mm3) θ (deg) reflns Tmax/Tmin data S R1a wR2b ∆Fmax/∆Fmin

C4H12O14P2Co3 522.87 triclinic P1h 4.7106(15) 8.051(3) 9.276(3) 107.164 94.284. 96.846 331.46(18) 1 2.619 4.030 259 0.16 × 0.06 × 0.04 2.31 to 28.26 2337/1469 0.8554/0.5649 1469/0/118 1.043 0.0445 0.1033 1.388/-0.659

C14H14N2O12P2V2 566.09 triclinic P1 4.8619(8) 10.3202(18) 10.4155(18) 63.888(3) 87.819(3) 86.393(3) 468.31(14) 1 2.007 1.243 284 0.19 × 0.08 × 0.05 2.18 to 27.00 2133/2133 0.9405/0.7982 2133/3/290 1.073 0.0647, 0.1620 0.0724, 0.1931 1.686/-0.777

C2H4O6PFe 210.87 orthorhombic P212121 6.6131(8) 8.3585(9) 9.6175(11) 90 90 90 531.61(11) 4 2.635 3.100 420 0.26 × 0.16 × 0.07 3.93 to 28.11 2308/1190 0.8122/0.4995 1190/0/99 1.026 0.0234, 0.0599 0.0236, 0.0600 0.395/-0.533

a

R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) [∑w(Fo2 - Fc2)2/∑w(Fo2)2]1/2.

trialkyl phosphonocarboxylate rather than phosphonocarboxylic acid removes the need to synthesize the acid because trialkyl phosphonocarboxylates are often far easier to purify (this can often be achieved by simple distillation procedures) than the corresponding phosphonocarboxylic acids; (2) the in situ slow formation of phosphonoacetic acid by hydrolysis of triethyl phosphonoacetate is advantageous to growth of single crystals sufficiently large to allow X-ray single-crystal structural determination. On the other hand, we noted that the presence of amines in the starting materials is important in the formation of compounds 1-6. The organic amines can act as templates, as structuredirecting agents, as second ligands or in a dual role.42 In the synthesis of 1-6, organic amines such as 4,4′-bipyridine, N,N′dimethylpiperazine, N-ethylpiperazine, and pyrazine were used

A Series of Metal Phosphonoacetates

Crystal Growth & Design, Vol. 6, No. 6, 2006 1447 Scheme 1.

Figure 1. View of the coordination environments of Zn atoms with 35% thermal ellipsoid (a), the inorganic ZnO ribbon (b), and 2D layered structure (c) in 1.

as starting materials, but only compounds 3, 4, and 6 contain them. This indicates that the organic amines in 1, 2, and 5 only act as additives. Moreover, organic 4,4′-bipyridine in 3 acts as a second ligand, while protonated 4,4′-bipyridinium and N,N′dimethylpiperazinium in 4 and 6 function as templates to adjust the network via hydrogen bonds and counterions to balance charge. Compound 7 was synthesized by reaction of FeSO4 and triethyl phosphonoaetate under acidic conditions, and white crystals indicated that Fe(II) ions were oxidized into high-spin Fe(III) ions. IR Spectra. Compounds 1, 2, 4, 5, and 7 show two broad bands at around 3430 and 3130 cm-1 confirming the presence of hydrogen bonded crystal lattice water. The IR spectra of 3 and 6 lack broad bands in this region, consistent with the absence of lattice water molecule. The presence of the CH2 group is indicated in 1-7 by weak peaks in the range of 2900-3100 cm-1. The stretching vibrations of the tetrahedral CPO3 group in 1-7 are indicated by the set of strong bands in the region of 900-1100 cm-1.11 The characteristic bands of carboxylate groups appear at 1656(as), 1588(as), 1438(s), and 1404(s) in 1,

Schematic View of the Possible Coordination Modes of Phosphonoacetate

1594(as) and 1396(s) cm-1 in 2, 1554(as), 1423(s), and 1388(s) cm-1 in 3, 1633(as), 1587(as), and 1426(s) in 4, 1540(as) and 1397(s) cm-1 in 5, 1492(as) and 1402(s) cm-1 in 6 and 1633(as), 1505(as), and 1397(s) cm-1 in 7 (as and s in parentheses mean the asymmetric and symmetric stretching vibration, respectively).43 The stretching vibration of 4,4′-bpy is indicated by a strong peak at 1617 cm-1 in 3 and 1623 cm-1 in 6. Crystal Structures. X-ray single-crystal diffraction reveals that 1 crystallizes in triclinic space group P1h, and the asymmetric unit consists of four crystallographically independent zinc atoms, two ppat, one hydroxide, and one coordinated water molecule as shown in Figure 1a. The Zn(1) site shows an octahedral geometry, being coordinated by five oxygen atoms from three different ppat ligands and one hydroxide ion. The Zn(1)-O bond lengths are in the range of 2.020(4)-2.142(5) Å. The cis O-Zn(1)-O angles are in the range of 81.02(19)-96.61(19)°. The Zn(2) site localizes an inversion center with site occupancy of 0.5 and also shows octahedral geometry, being coordinated by four oxygen atoms from four different ppat ligands and two hydroxide ions. The Zn(2)-O bond lengths are in the range of 2.001(5)-2.374(5) Å. The cis O-Zn(2)-O angles are in the range of 85.79(18)-94.21(18)°, while three trans O-Zn(2)-O angles are 180°. The Zn(3) site shows a tetrahedral geometry, being coordinated by three oxygen atoms from three ppat ligands and one hydroxide ion. The Zn(3)-O bond lengths are in the range of 1.943(5)-1.999(5) Å. The O-Zn(3)-O angles are in the range of 89.4(2)-113.3(2)°. The Zn(4) site shows a trigonal bipyramidal geometry, being coordinated by O(6), O(2), and O(5) atoms from three ppat ligands within the equatorial plane and O(1) and O(1w) at apical sites. The Zn(4)-O bond lengths are in the range of 1.945(5)-2.136(6) Å. The O(1d)-Zn(4)O(1w) angle is 171.2(2)°. The ppat exhibits two types of modes, Scheme 1G, µ5, and Scheme 1I, µ6. Interestingly, edge- and corner-sharing connections of ZnO6 octahedra, ZnO5 trigonal bipyramids, and ZnO4 tetrahedra generate unprecedented inorganic ZnO ribbons (Figure 1b), which are further linked by ppat into 2D organic-inorganic hybrid layers (Figure 1c). The hydrogen bonds between O1w and O6 extend the 2D organicinorganic hybrid layers into 3D hydrogen arrays (Figure S1, Supporting Information). Compound 2 crystallizes in the orthorhombic noncentrosymmetric space group Pna21, and the asymmetric unit consists of one crystallographically independent zinc atom, one ppat, and one protonated water molecule as shown in Figure 2a. The Zn(1) site shows a tetrahedral geometry, coordinated by three

1448 Crystal Growth & Design, Vol. 6, No. 6, 2006

Hou and Zhang

Figure 2. View of the coordination environment of Zn with 35% thermal ellipsoids (a) and the 3D open framework showing 1D dumbbell-shaped channels (b) in 2.

phosphonate oxygen atoms from three different ppat ligands and one carboxylate oxygen atom from an additional ppat ligand. Each of the three oxygen atoms of the PO3 group coordinates only one zinc atom. The coordination mode of PO3 in 2 is referred to as a (1,1,1) connection, which in combination with one additional carboxylate oxygen atom furnishes Scheme 1E, µ4: η1: η1: η1: η1 coordination mode. For phosphonate-carboxylate O3P-R-CO2 ligands, µ4: η1: η1: η1: η1 coordination is commonly observed when the R group is ethylene or longer alkylene groups, and examples include Zn(O3PC2H4CO2H)‚ 1.5H2O, and Na[Zn(O3PC2H4CO2)]‚H2O. However, for the ppat ligand, µ4: η1: η1: η1: η1 coordination is relatively seldomly observed due to chelation of -PO3 and -CO2 oxygen atoms to form stable six-membered rings.8,22,36,37 The Zn(1)-O bond lengths are in the range of 1.944(3)-1.948(2) Å. The O-Zn(1)-O angles are in the range of 102.63(12)-114.11(12)°, which shows a little deviation from the ideal 109.5°. The cornersharing connections of CPO3 and ZnO4 tetrahedra result in a 2-fold screwed ladder along the c-axis direction. The ladders are cross-linked by the organic part of ppat to form a 3D open framework with 1D dumbbell-shaped channels (Figure 2b). Each channel is enclosed by 24 atoms with a size of ca. 3.4-7.2 Å. The protonated water molecules are trapped in the channels. Compound 2 is isostructural with NH4[Zn(ppat)], reported by Liao, in which the ammonium cations are trapped in the channels.44 Compound 3 crystallizes in the monoclinic noncentrosymmetric space group Cc, and the asymmetric unit consists of three crystallographically independent zinc atoms, two ppat groups, and one 4,4′-bpy as shown in Figure 3a. All the three zinc sites show tetrahedral geometry. The Zn(1) atom is coordinated by two nitrogen atoms from two 4,4′-bpy and two carboxylate

Figure 3. View of the coordination environments of Zn atoms with 35% thermal ellipsoids (a), the layered structural motif [Zn(ppat)]nn(b), and the 3D framework (c) in 3.

oxygen atoms from two ppat ligands. The Zn(2) and Zn(3) atoms show similar coordination geometry, both coordinated by three PO3 oxygen atoms and one carboxylate oxygen from three different ppat ligands. The coordination mode of ppat is Scheme 1D, µ4. The Zn(1)-N bond lengths are 2.016(4) and 2.031(4) Å. The Zn-O bond lengths are in the range of 1.906(4)2.035(4) Å. The L-Zn-L angles are in the range of 101.82(13)-113.21(16)°. Compound 3 consists of two structural motifs, and they are [Zn(4,4′-bpy)]n2n+ chains and [Zn(ppat)]nnlayers (Figure 3b). The fusion of [Zn(ppat)]nn- layers and [Zn(4,4′-bpy)]2+ chains via Zn-O bonds generates a 3D framework (Figure 3c).

A Series of Metal Phosphonoacetates

Crystal Growth & Design, Vol. 6, No. 6, 2006 1449

Figure 4. View of the coordination environment of the Zn atom with 35% thermal ellipsoids (a) and the 2D layered structural motif [Zn(ppat)]nn- (b) in 4.

The asymmetric unit of 4 consists of one crystallographically independent zinc atom, one ppat, half of a H2dmpz, and one crystal lattice water molecule (Figure 4a). The Zn(1) site shows a tetrahedral geometry, being coordinated by three PO3 oxygen atoms and one carboxylate oxygen from three different ppat ligands. The ppat coordinates to three Zn(II) sites in Scheme 1D coordination mode. The Zn(1)-O bond lengths are in the range of 1.9161(11)-1.9825(13) Å. The O-Zn(1)-O angles are in the range of 101.64(5)-113.18(5)°. The coordination of Zn and ppat groups result in a 2D anionic layer with formula [Zn(ppat)]nn- (Figure 4b). The [Zn(ppat)]nn- layers are arranged in AA fashion, and the H2dmpz cations fill the interlayer space via N-H‚‚‚O hydrogen bond interactions (Figure S2, Supporting Information). The asymmetric unit in 5 consists of two independent Co(II) atoms, one ppat, one hydroxide, and and one water molecule as shown in Figure 5a. To keep charge balance, one extra hydrogen atom is required on one of the five oxygen atoms of ppat or the water molecule. Because all five oxygen atoms of ppat are coordinated to Co(II) atoms, there is little possibility of hydrogen attached to oxygen of ppat. Thus we deduced the protonation of the water molecule. The Co(1) atom shows octahedral geometry with site occupancy of 0.5, being coordinated by four oxygen atoms from four different ppat ligands and two hydroxide ions. The Co(1)-O bond lengths are in the range of 2.051(3)-2.194(4) Å. The cis O-Co(1)-O angles are in the range of 81.29(13)-98.71(13)°. The Co(2) also shows octahedral geometry, being coordinated by five oxygen atoms from four different ppat ligands and one hydroxide ion. The Co(2)-O bond lengths are between 2.077(3) and 2.165(4) Å. The cis O-Co(2)-O angles are between 99.23(13)° and 80.99(13)°. A different chelate bidentate mode is found in a mononuclear compound;45 the coordination mode of -PO3 in

Figure 5. View of the coordination environments of Co atoms with 35% thermal ellipsoids (a), one-dimensional ribbon [Co(ppat)]nn- (b), and the 2D layered structure (c) in 5.

5 is referred to as a (2,1,2) connection, which in combination with two carboxylate oxygen atoms furnishes Scheme 1H, µ6 coordination mode of ppat. The Co(1)O6 and Co(2)O6 octahedra share edges to form inorganic Co-O chain with sequence of -Co(2)-C(2)-Co(1)- (Figure 5b), and adjacent Co-O chains are held together by ppat to generate two-dimensional layers (Figure 5d). Alternately, the layered structure of 5 is constructed from [Co(2)ppat]nn- ribbons (Figure 5c) that are mutually linked by Co(1) atoms via Co(1)-O bonds. Compound 6 crystallizes in the rare space group P1. We tried to solve the structure from the centrosymmetric space group P1h but failed. In addition, calculation by PLATON also shows that the P1 space group is correct. The asymmetric unit consists of two independent V(IV) atoms, two oxygen atoms, two ppat groups, and one doubly protonated 4,4′-bpy cation as shown in Figure 6. All atoms localize in general positions. Each V(IV)

1450 Crystal Growth & Design, Vol. 6, No. 6, 2006

Hou and Zhang

Figure 8. χmT versus T curves for 5 measured at an applied field of 1 kOe.

Figure 6. View of the coordination environments of V atoms with 35% thermal ellipsoids (a) and the layered structure motif [VO(ppat)]nn(b) in 6.

Figure 9. χmT versus T curves for 6 measured at an applied field of 5 kOe.

Figure 7. View of the coordination environment of the Fe atom with 35% thermal ellipsoids (a) and 3D structure of 7 along the a-axis direction (b).

has a square pyramidal geometry, coordinated by one terminal oxygen at the axial position (VdO distances 1.576(11) and 1.610(12) Å) and four bridged oxygen atoms in the equatorial plane (V-O bond lengths 1.930(8)-2.025(10) Å). The valence sum46 and empirical formula47 calculations confirmed that both crystallographically independent vanadium atoms are tetravalent. The ppat shows Scheme 1C, µ3 coordination mode. Compound 6 has a 3D supramolecular array formed by [VO(ppat)]n2nlayers and H24,4′-bpy cations via N-H‚‚‚O hydrogen bonds. The two-dimensional [VO(ppat)]n2n- layer is constructed from vanadyl (VdO) and µ3-ppat groups via V-O bonds. Compound 7 crystallizes in the orthorhombic chiral space group P212121, and the asymmetric unit consists of one crystallographically independent Fe(III) atom, one ppat, and one coordinated water molecule as shown in Figure 7a. The Fe(III)

atom adopts octahedral geometry, being coordinated by five oxygen atoms from four different ppat ligands and one water molecule. The Fe-O bond lengths are between 1.919(2)2.103(2) Å. The cis O-Fe(1)-O angles range from 81.65(11)° to 97.22(10)°. The coordination mode of ppat is Scheme 1D, µ4. Each Fe(III) is connected to four ppat groups and vice versa, which results in a 3D four-connected framework with diamond topology. Compound 7 is the supramolecular isomer of MIL49,36 which has a two-dimensional structure containing dimers of edge-sharing FeO5(H2O) octahedra and ppat groups. Different from MIL-49, compound 7 is a chiral three-dimensional framework contaning 3D isolated FeO5(H2O) octahedra (Figure 7b). Magnetic Properties. The temperature dependence of the magnetic susceptibility was measured on a polycrystalline sample of 5 in the temperature range of 2-300 K under 1 kOe (Figure 8). The χmT value at 300 K is 9.03 cm3 K mol-1, which is higher than the spin-only value for three isolated Co(II) ions (5.625 cm3 K mol-1), in accordance with the well-documented orbital contribution of high-spin Co(II) ions.48 As the temperature is lowered, the χmT value steadily decreases and reaches 0.378 cm3 mol-1 K at 2 K, indicating antiferromagnetic coupling. Above 20 K, the inverse magnetic susceptibility versus temperature obeys the Curie-Weiss law χm ) C/(T - θ), where C ) 9.559 cm3 K mol-1 and θ ) -13.2 K. This gives an average g value of 2.53, which is reasonable due to the large anisotropy of Co(II) ions. The main magnetic exchange pathways in 5 can be propagated via bis(µ-oxo), µ-O,O′carboxylato, and µ-O,O′-phosphonato bridges. If we have only the nearest superexchange interactions between Co centers via bis(µ-oxo) bridges (Co-Co distances 3.187 and 3.183 Å) taken into account, weak ferromagnetic coupling generally would be

A Series of Metal Phosphonoacetates

Crystal Growth & Design, Vol. 6, No. 6, 2006 1451

superexhange interaction. The magnetic behavior of 6 is consistent with large separation between V(IV) centers. The variable-temperature magnetic susceptibilities of 7 have been measured on a crystalline sample in a field of 5 kOe (Figure 10). A plot of χmT vs T shows that the χmT value at 300 K is 3.66 cm3 K mol-1, which is lower than the spin-only value for high-spin Fe(III) ion (4.37 cm3 K mol-1, g ) 2.0), indicating rather antiferromagnetic coupling even at room temperature. The inverse magnetic susceptibility gives clear evidence of antiferromagnetic behavior above 30 K. The Curie constant determined in the range 30-300 K is 4.71 cm3 K mol-1, which is close to the theoretical spin-only value (4.37) for a high-spin-state Fe(III) ion. The Curie-Weiss temperature θ is -78.1 K. The Curie constant in combination with charge balance and the white color of the crystals confirms +3 valence of the Fe atom. Compound 7 shows a magnetic hysteresis loop (Hc ≈ 800 Oe and Mr ) 33 cm3/mol) characteristic of canted antiferromagnetic behavior.50 The canting of spins is consistent with the lack of inversion center between neighboring Fe(III) ions. Conclusions Seven new metal phosphonoacetates were synthesized by hydrothermal in situ hydrolysis of triethyl phosphonoacetates, and a variety of coordination modes of the phosphonoacetates in combination with different metal ions and possible second ligands (or templates) resulted rich structures. The work further confirmed that, compared with traditional methods for metal phosphonates, hydrothermal in situ hydrolysis of triethyl phosphonoacetates is a better route for growing single crystals suitable for X-ray single crystal structural analyses. When metal ions containing unpaired electrons were used, some interesting magnetic behavior such as spin canting can be expected. Acknowledgment. This work was financially supported by NNSFC (Grant 20401011), Foundation for the Author of National Excellent Doctoral Dissertation of PR China (Grant 200422), Youth Foundation of Shanxi (Grant 20041009), and Education Bureau of Shanxi. Supporting Information Available: Crystallographic data in CIF format, 3D packing arrays for compounds 1, 4, and 6, and χm vs T curves for compounds 5 and 6. This material is available free of charge via the Internet at http://pubs.acs.org. Figure 10. χmT (a) and χm (b) versus T curves for 7 measured at an applied field of 5 kOe and (c) Magnetic hysteresis loop at 2 K. The inset in panel b is the χm-1 versus T curve.

expected by analysis of Co-O-Co angles [Co-O-Co angles 94.0°, 99.1°, and 99.4°].49 The expectation is not consistent with the experimental result, which indicates that the next nearest superexchange interactions via µ-O,O′-carboxylato and µ-O,O′phosphonato bridges play an important role in the magnetic behavior. The variable-temperature magnetic susceptibilities of 6 have been measured on a crystalline sample in a field of 5 kOe (Figure 9). A plot of χmT vs T for 6 shows that the χmT value at 320 K is 0.83 cm3 K mol-1, which is in agreement with two isolated V(IV) ions (for g ) 2.10). As the temperature is lowered, the χmT value steadily decreases and reaches 0.548 cm3 mol-1 K at 2 K. The linear fit of inverse magnetic susceptibility between 2 and 320 K by the Curie-Weiss equation, χm ) C/(T - θ), gives Curie constant C ) 0.825 cm3 K mol-1 and θ ) -3.8 K, which indicates rather weak

References (1) Maeda, K. Microporous Mesoporous Mater. 2004, 73, 47. (2) Clearfield, A. Chem. Mater. 1998, 10, 2801. (3) Cheetham, K.; Ferey, G.; Loiseau, T. Angew. Chem., Int. Ed. 1999, 38, 3268. (4) Bellitto, A. C.; Ibrahim, S. A.; Mahmoud, M. R.; Rizzi, R. J. Chem. Soc., Dalton Trans. 2000, 3913. (5) Bujoli, B.; Pena, O.; Palvadeau, P.; Bideau, J. L.; Payen, C.; Rouxelt, J. Chem. Mater. 1993, 5, 583. (6) Neff, G. A.; Helfrich, M. R.; Clifton, M. C.; Page, C. J. Chem. Mater. 2000, 12, 2363. (7) Bideau, J. L.; Payen, C.; Palvadeau, P.; Bujoli, B. Inorg. Chem. 1994, 33, 4885. (8) Zhu, J.; Bu, X.; Feng, P.; Stucky, G. D. J. Am. Chem. Soc. 2000, 122, 11563. (9) Guliants, V. V.; Benziger, J. B.; Sundaresan, S. Chem. Mater. 1995, 7, 1493. (10) Amicangelo, J. C.; Rosenthal, G. L.; Leenstra, W. R. Chem. Mater. 2003, 15, 390. (11) Zhang, B.; Poojary, D. M.; Clearfield, A. Inorg. Chem. 1998, 37, 1844. (12) Poojary, D. M.; Zhang, B.; Clearfield, A. Chem. Mater. 1999, 11, 421.

1452 Crystal Growth & Design, Vol. 6, No. 6, 2006 (13) LaDuca, R.; Rose, D.; DeBord, J. R. D.; Haushalter, R. C.; O’Connor, C. J.; Zubieta, J. J. Solid State Chem. 1996, 123, 408. (14) Mao, J.-G.; Clearfield, A. Inorg. Chem. 2002, 41, 2319. (15) Drumel, S.; Janvier, P.; Barbom, P.; Bujoli-Doeuff, M.; Bujoli, B. Inorg. Chem. 1995, 34, 148. (16) Hartman, S. J.; Todorov, E.; Cruz, C.; Sevov, S. C. Chem. Commun. 2000, 1213. (17) Zhang, Y.; Scott, K. J.; Clearfield, A. Chem. Mater. 1993, 5, 495. (18) Kijima, T.; Watanabe, S.; Machida, M. Inorg. Chem. 1994, 33, 2586. (19) Doran, M. B.; Norquist, A. J.; O’Hare, D. Chem. Mater. 2003, 15, 1449. (20) Khan, M. I.; Lee, Y.-S.; O’Connor, C. J.; Haushalter, R. C.; Zubieta, J. J. Am. Chem. Soc. 1994, 116, 4525. (21) Zheng, L.-M.; Duan, C.-Y.; Ye, X.-R.; Zhang, L.-Y.; Wang, C.; Xin, X.-Q. J. Chem. Soc., Dalton Trans. 1998, 905. (22) Stock, N.; Frey, S. A.; Stucky, G. D.; Cheetham, A. K. J. Chem. Soc., Dalton Trans. 2000, 4292. (23) Distler, A.; Sevov, S. C. Chem. Commun. 1998, 959. (24) Rabu, P.; Janvier, P.; Bujoli, B. J. Mater. Chem. 1999, 9, 1323. (25) Serpaggi, F.; Ferey, G. Inorg. Chem. 1999, 38, 4741. (26) Riou-Cavellec, M.; Sanselme, M.; Guillou, N.; Ferey, G. Inorg. Chem. 2001, 40, 723. (27) Ayyappan, S.; Delgado, G. D.; Cheetham, A. K.; Fe´rey, G.; Rao, C. N. R. J. Chem. Soc., Dalton Trans. 1999, 2905. (28) Hix, G. B.; Kariuki, B. M.; Kitchin, S.; Tremayne, M. Inorg. Chem. 2001, 40, 1477. (29) Jankovics, H.; Daskalakis, M.; Raptopoulou, C. P.; Terzis, A.; Tangoulis, V.; Giapintzakis, J.; Kiss, T.; Salifoglou, A. Inorg. Chem. 2002, 41, 3366. (30) Massiot, D.; Drumel, S.; Janvier, P.; Bujoli-Doeuff, M.; Bujoli, B. Chem. Mater. 1997, 9, 6. (31) Poojary, D. M.; Zhang, B.; Bellinghausen, P.; Clearfield, A. Inorg. Chem. 1996, 35, 5254.

Hou and Zhang (32) Poojary, D. M.; Zhang, B.; Bellinghausen, P.; Clearfield, A. Inorg. Chem. 1996, 35, 4942. (33) Serre, C.; Ferey, G. Inorg. Chem. 2001, 40, 5350. (34) Serre, C.; Ferey, G. Inorg. Chem. 1999, 38, 5370. (35) Zhang, X.-M. Coord. Chem. ReV. 2005, 249, 1201 and references therein. (36) Sanselme, M.; Riou-Cavellec, M.; Greneche, J.-M.; Ferey, G. J. Solid State Chem. 2002, 164, 354. (37) Hix, G. B.; Turner, A.; Kariuki, B. M.; Tremayne, M.; MacLean, E. J. J. Mater. Chem. 2002, 12, 3220. (38) Zhang, X.-M. Eur. J. Inorg. Chem. 2004, 544. (39) Zhang, X.-M.; Fang, R.-Q.; Wu, H.-S. Cryst. Growth Des. 2005, 5, 1335. (40) Sheldrick, G. M. SHELX-97, Program for X-ray Crystal Structure Solution and Refinement; Go¨ttingen University: Germany, 1997. (41) Spek, A. L. PLATON, version 1.07. J. Appl. Crystallogr. 2003, 36, 7. (42) Choudhury, A.; Natarajan, S.; Rao, C. N. R. Inorg. Chem. 2000, 39, 4295. (43) Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coordination Compounds; John Wiley & Sons: New York, 1986. (44) Liao, J.-H.; Wu, P.-C.; Bai, Y.-H. Inorg. Chem. Commun. 2005, 8, 390. (45) Slepokura, K.; Piatkowska, A.; Lis, T. Z. Kristallogr. 2002, 217, 614. (46) Brown, D.; Altermatt, D. Acta Crystallogr., Sect. B 1985, 41, 244. (47) Schindler, M.; Hawthorne, F. C.; Baur, W. H. Chem. Mater. 2000, 12, 1248. (48) Humphrey, S. M.; Wood, P. T. J. Am. Chem. Soc. 2004, 126, 13236. (49) Kahn, O. Molecular Magnetism; Wiley-VCH: New York, 1993. (50) Gao, E.-Q.; Wang, Z.-M.; Yan, C.-H. Chem. Commun. 2003, 1748.

CG0600750