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Acta Cryst. (2009). E65, m183    [ doi:10.1107/S1600536808028456 ]

A second modification of poly[diaquadi-[mu]-citrato(3-)-trizinc(II)]

X.-H. Li, W.-L. Chen and E.-B. Wang

Abstract top

A second modification of the zinc(II) coordination polymer with citric acid, [Zn3(C6H5O7)2(H2O)2]n or [Zn(citrate)2(H2O)2], has been synthesized under hydrothermal conditions by reacting zinc acetate with citric acid. The structure contains two unique Zn atoms, one with a distorted octahedral coordination and located on an inversion centre, and one with a distorted tetrahedral coordination. The ZnO6 and ZnO4 units are linked into layers extending parallel to (010).

Comment top

The design and synthesis of coordination polymers with extended frameworks has drawn great attention due to their potential applications in catalysis, ligand exchange and their physical properties (Yaghi et al., 1996; Bourne et al., 2001). The coordination chemistry of biologically relevant transition metal ions toward citric acid has been widely investigated (Liu et al., 2005; Xie et al., 2005.) In this work, a new zinc(II) coordination polymer with citric acid (1) has been synthesized. The structure of (1) is reported here, shown in Fig. 1.

In (1) a compact layered structure is evident. An isolated Zn(1) ion is situated on an inversion center and is linked with two symmetry-related citrate ligands. It is surrounded in a distorted octahedral coordination by six oxygen atoms from four carboxylate oxygen atoms and two hydroxyl oxygen atoms from the citrate ligands. The Zn(1)—O distance are in the range of 2.0707 (18) - 2.1029 (18) Å. The Zn(2) ion is coordinated by three oxygen atoms from three carboxylate ligands and an oxygen from a water molecule in a distorted tetrahedral coordination. The Zn(2)—O distances are in the range of 1.9475 (19) - 2.0141 (19) Å. The ZnO6 and ZnO4 units are linked into a layer structure extending parallel to the ac plane (Fig. 2).

Recently, another polymorph of a compound with this composition has been reported by Wu (2008). The main structural difference of (1) and the first polymorph is the coordination of the zinc cations. In the first polymorph solely ZnO6 units are present. However, by linking the structural units, a layered structure is likewise formed in this polymorph.

Related literature top

For the structure of the first polymorph, see: Wu (2008). For general background, see Bourne et al. (2001); Yaghi et al. (1996). Biologically relevant transition-metal citrate compounds have bee reported by Liu et al. (2005) and Xie et al. (2005).

Experimental top

Compound (1) was prepared from a weak acidic mixture of zinc acetate (0.255 g, 1 mmol), citric acid (0.49 g, 1.5 mmol) and a 15 ml alcohol/water mixture, which was sealed in a 30 ml Teflon-lined steel vessel and kept at 433 K under autogenously pressure for three d. After cooling, yellow crystals were isolated and air-dried with a yield of approximately 63%.

Refinement top

All H-atoms bound to carbon were refined using a riding model with d(C—H) = 0.97 Å and Uiso(H) = 1.5Ueq(C). H atoms of the water molecule were located in difference maps and refined isotropically with d(O—H) = 0.85 Å and Uiso(H) = 1.5Ueq(O).

Computing details top

Data collection: RAPID-AUTO (Rigaku, 1998); cell refinement: RAPID-AUTO (Rigaku, 1998); data reduction: RAPID-AUTO (Rigaku, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL-Plus (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. A view of the molecule of (1). Displacement ellipsoids are drawn at the 70% probability level. Hydrogen atoms are drawn as small circles of arbitrary radius.
[Figure 2] Fig. 2. 2-D packing arrangement of (1) viewed along the b axis. Color codes: Zn (yellow), O (red), C (grey). Hydrogen atoms are omitted for clarity.
poly[diaquadi-µ-citrato(3-)-trizinc(II)] top
Crystal data top
[Zn3(C6H5O7)2(H2O)2]Z = 1
Mr = 610.34F(000) = 304
Triclinic, P1Dx = 2.312 Mg m−3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 6.4649 (13) ÅCell parameters from 2026 reflections
b = 7.2666 (15) Åθ = 3.3–27.5°
c = 9.6951 (19) ŵ = 4.16 mm−1
α = 85.27 (3)°T = 298 K
β = 77.31 (3)°Block, yellow
γ = 80.99 (3)°0.28 × 0.26 × 0.22 mm
V = 438.29 (15) Å3
Data collection top
Rigaku R-AXIS RAPID IP
diffractometer		2004 independent reflections
Radiation source: fine-focus sealed tube1763 reflections with I > 2σ(I)
graphiteRint = 0.029
ω–scansθmax = 27.5°, θmin = 3.3°
Absorption correction: multi-scan
ABSCOR (Higashi, 1995)		h = −8→8
Tmin = 0.389, Tmax = 0.461k = −9→9
4339 measured reflectionsl = −12→12
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.027Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.066H atoms treated by a mixture of independent and constrained refinement
S = 1.03 w = 1/[σ2(Fo2) + (0.0291P)2 + 0.3186P]
where P = (Fo2 + 2Fc2)/3
2004 reflections(Δ/σ)max < 0.001
146 parametersΔρmax = 0.87 e Å−3
0 restraintsΔρmin = −0.60 e Å−3
Crystal data top
[Zn3(C6H5O7)2(H2O)2]γ = 80.99 (3)°
Mr = 610.34V = 438.29 (15) Å3
Triclinic, P1Z = 1
a = 6.4649 (13) ÅMo Kα radiation
b = 7.2666 (15) ŵ = 4.16 mm−1
c = 9.6951 (19) ÅT = 298 K
α = 85.27 (3)°0.28 × 0.26 × 0.22 mm
β = 77.31 (3)°
Data collection top
Rigaku R-AXIS RAPID IP
diffractometer		2004 independent reflections
Absorption correction: multi-scan
ABSCOR (Higashi, 1995)		1763 reflections with I > 2σ(I)
Tmin = 0.389, Tmax = 0.461Rint = 0.029
4339 measured reflectionsθmax = 27.5°
Refinement top
R[F2 > 2σ(F2)] = 0.027H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.066Δρmax = 0.87 e Å−3
S = 1.03Δρmin = −0.60 e Å−3
2004 reflectionsAbsolute structure: ?
146 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

The highest residual peak, 0.871 e A3, is close to O (1) (with the distance of ca 0.967 A), to C(1) with the distance of ca 1.296 A, but featureless. The deepest hole is -0.604 e A3.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Zn10.00000.00000.00000.02280 (11)
Zn20.43151 (4)−0.21372 (4)0.32805 (3)0.02389 (10)
C1−0.1926 (4)0.3065 (4)0.4125 (2)0.0263 (5)
C2−0.0112 (4)0.3838 (3)0.3087 (2)0.0220 (5)
H2A0.10330.39240.35690.026*
H2B−0.06240.50870.27560.026*
C30.0768 (3)0.2625 (3)0.1818 (2)0.0179 (4)
C40.2481 (4)0.3533 (3)0.0755 (2)0.0224 (5)
H4A0.19080.48270.05820.027*
H4B0.36980.35270.11890.027*
C50.3282 (4)0.2647 (3)−0.0660 (2)0.0213 (5)
C60.1701 (4)0.0658 (3)0.2287 (2)0.0198 (4)
O1−0.2934 (4)0.1977 (5)0.3701 (2)0.0669 (9)
O2−0.2314 (3)0.3509 (3)0.53876 (18)0.0344 (5)
O30.2747 (3)0.1149 (3)−0.09162 (18)0.0300 (4)
O40.4538 (3)0.3523 (3)−0.15702 (18)0.0300 (4)
O50.2952 (3)0.0518 (3)0.31332 (18)0.0260 (4)
O60.1257 (3)−0.0737 (2)0.17968 (19)0.0324 (4)
O7−0.0943 (3)0.2466 (2)0.11071 (17)0.0210 (3)
O80.6828 (3)−0.1961 (3)0.41525 (19)0.0334 (4)
H20.7285−0.09270.38850.050*
H10.6486−0.20040.50510.050*
H1A−0.191 (6)0.237 (5)0.173 (4)0.049 (11)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Zn10.0297 (2)0.0247 (2)0.01762 (18)−0.01201 (16)−0.00723 (15)−0.00034 (15)
Zn20.02577 (16)0.02446 (16)0.01887 (15)−0.00433 (11)0.00168 (10)−0.00202 (11)
C10.0259 (12)0.0329 (13)0.0189 (10)−0.0080 (10)0.0010 (9)−0.0016 (10)
C20.0240 (11)0.0246 (12)0.0160 (10)−0.0050 (9)0.0003 (8)−0.0023 (9)
C30.0198 (10)0.0219 (11)0.0130 (9)−0.0066 (9)−0.0025 (8)−0.0018 (8)
C40.0256 (12)0.0246 (12)0.0168 (10)−0.0103 (9)0.0010 (9)−0.0011 (9)
C50.0185 (11)0.0260 (12)0.0182 (10)−0.0029 (9)−0.0011 (8)−0.0014 (9)
C60.0210 (11)0.0242 (11)0.0140 (9)−0.0064 (9)−0.0011 (8)−0.0010 (9)
O10.0598 (15)0.119 (2)0.0318 (11)−0.0641 (17)0.0145 (10)−0.0292 (14)
O20.0445 (11)0.0434 (11)0.0162 (8)−0.0231 (9)0.0056 (7)−0.0072 (8)
O30.0324 (10)0.0317 (10)0.0256 (9)−0.0144 (8)0.0045 (7)−0.0106 (8)
O40.0338 (10)0.0315 (10)0.0215 (8)−0.0144 (8)0.0094 (7)−0.0056 (7)
O50.0269 (9)0.0278 (9)0.0254 (8)−0.0009 (7)−0.0118 (7)−0.0031 (7)
O60.0510 (12)0.0192 (9)0.0351 (10)−0.0106 (8)−0.0243 (9)0.0041 (7)
O70.0204 (8)0.0277 (9)0.0157 (7)−0.0045 (7)−0.0047 (6)−0.0013 (6)
O80.0377 (11)0.0377 (11)0.0253 (9)−0.0043 (8)−0.0086 (8)−0.0020 (8)
Geometric parameters (Å, °) top
Zn1—O32.0707 (18)C3—O71.449 (3)
Zn1—O3i2.0707 (18)C3—C41.529 (3)
Zn1—O6i2.0768 (18)C3—C61.535 (3)
Zn1—O62.0768 (18)C4—C51.515 (3)
Zn1—O7i2.1029 (18)C4—H4A0.9700
Zn1—O72.1029 (18)C4—H4B0.9700
Zn2—O2ii1.9475 (19)C5—O31.252 (3)
Zn2—O4iii1.9528 (18)C5—O41.264 (3)
Zn2—O51.9992 (19)C6—O61.252 (3)
Zn2—O82.0141 (19)C6—O51.261 (3)
C1—O11.245 (3)O2—Zn2ii1.9475 (19)
C1—O21.254 (3)O4—Zn2iii1.9528 (18)
C1—C21.516 (3)O7—H1A0.78 (4)
C2—C31.526 (3)O8—H20.8500
C2—H2A0.9700O8—H10.8500
C2—H2B0.9700
O3—Zn1—O3i180.00 (9)O7—C3—C2109.47 (18)
O3—Zn1—O6i91.13 (8)O7—C3—C4107.60 (17)
O3i—Zn1—O6i88.87 (8)C2—C3—C4110.10 (18)
O3—Zn1—O688.87 (8)O7—C3—C6108.42 (17)
O3i—Zn1—O691.13 (8)C2—C3—C6110.98 (18)
O6i—Zn1—O6180.00 (11)C4—C3—C6110.19 (19)
O3—Zn1—O7i94.73 (7)C5—C4—C3116.49 (18)
O3i—Zn1—O7i85.27 (7)C5—C4—H4A108.2
O6i—Zn1—O7i78.62 (7)C3—C4—H4A108.2
O6—Zn1—O7i101.38 (7)C5—C4—H4B108.2
O3—Zn1—O785.27 (7)C3—C4—H4B108.2
O3i—Zn1—O794.73 (7)H4A—C4—H4B107.3
O6i—Zn1—O7101.38 (7)O3—C5—O4122.0 (2)
O6—Zn1—O778.62 (7)O3—C5—C4122.6 (2)
O7i—Zn1—O7180.00 (8)O4—C5—C4115.4 (2)
O2ii—Zn2—O4iii109.95 (8)O6—C6—O5122.3 (2)
O2ii—Zn2—O5108.17 (9)O6—C6—C3119.8 (2)
O4iii—Zn2—O5119.97 (8)O5—C6—C3117.8 (2)
O2ii—Zn2—O8108.62 (8)C1—O2—Zn2ii116.04 (16)
O4iii—Zn2—O8106.38 (8)C5—O3—Zn1128.61 (16)
O5—Zn2—O8103.11 (8)C5—O4—Zn2iii111.81 (15)
O1—C1—O2122.6 (2)C6—O5—Zn2108.96 (16)
O1—C1—C2118.9 (2)C6—O6—Zn1111.25 (16)
O2—C1—C2118.5 (2)C3—O7—Zn1106.24 (13)
C1—C2—C3112.11 (19)C3—O7—H1A103 (3)
C1—C2—H2A109.2Zn1—O7—H1A111 (3)
C3—C2—H2A109.2Zn2—O8—H2109.3
C1—C2—H2B109.2Zn2—O8—H1111.9
C3—C2—H2B109.2H2—O8—H1107.6
H2A—C2—H2B107.9
Symmetry codes: (i) −x, −y, −z; (ii) −x, −y, −z+1; (iii) −x+1, −y, −z.
Table 1
Selected geometric parameters (Å) top
Zn1—O32.0707 (18)Zn2—O4ii1.9528 (18)
Zn1—O62.0768 (18)Zn2—O51.9992 (19)
Zn1—O72.1029 (18)Zn2—O82.0141 (19)
Zn2—O2i1.9475 (19)
Symmetry codes: (i) −x, −y, −z+1; (ii) −x+1, −y, −z.
Acknowledgements top

This work was supported by the National Natural Science Foundation of China (20701005/20701006), the Analysis and Testing Foundation of Northeast Normal University and the Ph. D Station Foundation of Ministry of Education (20060200002).

references
References top

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