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Acta Cryst. (2008). E64, m581    [ doi:10.1107/S1600536808006624 ]

Hexaaquazinc(II) dipicrate

S. Natarajan, K. V. Vijitha, S. A. M. B. Dhas, J. Suresh and P. L. N. Lakshman

Abstract top

In the title compound, [Zn(H2O)6](C6H2N3O7)2, the ZnII ion is located on an inversion center and is coordinated by six water molecules in an octahedral geometry. The picrate anions have no coordination interactions with the ZnII atom. The three nitro groups are twisted away from the attached benzene ring by19.8 (3), 6.5 (4) and 28.6 (3)°. There are numerous O-H...O hydrogen bonds in the crystal structure.

Comment top

Picric acid forms salts with many organic and metallic cations (Gartland et al., 1974). Picrates with various degrees of hydration are formed by metals (e.g. Li, Na), the alkaline earths (e.g. Cd, Hg) and various transition metals (e.g. Al, Y). Crystal structures have been reported for isomorphous NH4 and K picrates (Maartmann-Moe, 1969), thallium picrate (Herbstein et al., 1977) and recently for manganese picrate (Liu et al., 2008). The present work reports the crystal structure of the title compound, a zinc picrate. This work is part of a systematic investigation on the structures of the metal complexes of picric acid.

In the crystal structure of the title compound, each ZnII ion is coordinated by the O atoms of six water molecules and not by the O atoms from the picrate anions. The Zn—O distances range from 2.0297 (16) to 2.1126 (17) Å. The coordination polyhedra around the ZnII ion can be described as a distorted octahedron. The picrate anion adopts a keto form with a C1—O1 bond distance of 1.242 (3) Å; the C6—C1 [1.457 (3) Å] and C2—C1 [1.456 (3) Å] bond distances are longer than the other C—C bond lengths of the benzene ring. The three nitro groups are twisted out of the attached benzene ring by 19.8 (3)° [N1/O2/O3], 6.5 (4)° [N2/O4/O5] and 28.6 (3)° [N3/O6/O7]. The twisting of the nitro groups may be attributed to the O—H···O hydrogen bonding interactions taking place between water and picrate O atoms. The C2—C1—C6 bond angle of 111.20 (18)° is narrower than the corresponding angle in picric acid (116.4 (5)°; Yang et al., 2001).

The packing of molecules is governed by large number of O—H···O hydrogen bonds (Table 1). π···π interactions are observed between the benzene rings of inversion related picrate ions, with a centroid to centroid distance of 3.6268 (11) Å (Fig. 2).

Related literature top

For related literature, see: Gartland et al. (1974); Herbstein et al. (1977); Liu et al. (2008); Maartmann-Moe (1969); Yang et al. (2001).

Experimental top

Colourless needle shaped single crystals of the title compound were grown from a saturated aqueous solution containing picric acid and zinc chloride in a 1:1 stoichiometric ratio.

Refinement top

O-bound H atoms were located in a difference Fourier map and their positional parameters were refined, with Uiso(H) = 1.5Ueq(O). Some of the O—H distances were restrained to 0.85 (2) Å. C-bound H atoms were placed at calculated positions and allowed to ride on their carrier atoms, with C—H = 0.93 Å, and Uiso = 1.2Ueq(C).

Computing details top

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS (Enraf–Nonius, 1994); data reduction: XCAD4 (Harms & Wocadlo, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound, showing 30% probability displacement ellipsoids and the atom-numbering scheme. Atoms labeled with the suffix a and double prime (") are generated by the symmetry operations (-x, 1 - y, 1 - z) and (1 - x,1 - y, 1 - z), respectively.
[Figure 2] Fig. 2. A packing diagram of the title compound. Dashed lines indicate π-π interactions.
Hexaaquazinc(II) dipicrate top
Crystal data top
[Zn(H2O)6](C6H2N3O7)2Z = 1
Mr = 629.68F000 = 320
Triclinic, P1Dx = 1.874 Mg m−3
Hall symbol: -P 1Mo Kα radiation
λ = 0.71073 Å
a = 7.8571 (4) ÅCell parameters from 25 reflections
b = 8.3311 (6) Åθ = 2–25º
c = 8.9897 (7) ŵ = 1.22 mm−1
α = 89.8350 (11)ºT = 293 (2) K
β = 83.097 (1)ºNeedle, colourless
γ = 72.8370 (9)º0.13 × 0.11 × 0.10 mm
V = 557.84 (7) Å3
Data collection top
Nonius MACH-3
diffractometer		Rint = 0.006
Radiation source: fine-focus sealed tubeθmax = 25.0º
Monochromator: graphiteθmin = 2.3º
T = 293(2) Kh = −1→9
ω–2θ scansk = −9→9
Absorption correction: ψ scan
(North et al., 1968)		l = −10→10
Tmin = 0.854, Tmax = 0.8862 standard reflections
2441 measured reflections every 60 min
1971 independent reflections intensity decay: none
1908 reflections with I > 2σ(I)
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.031H atoms treated by a mixture of
independent and constrained refinement
wR(F2) = 0.087  w = 1/[σ2(Fo2) + (0.0559P)2 + 0.2704P]
where P = (Fo2 + 2Fc2)/3
S = 1.14(Δ/σ)max = 0.001
1971 reflectionsΔρmax = 0.43 e Å−3
196 parametersΔρmin = −0.71 e Å−3
4 restraintsExtinction correction: none
Primary atom site location: structure-invariant direct methods
Crystal data top
[Zn(H2O)6](C6H2N3O7)2γ = 72.8370 (9)º
Mr = 629.68V = 557.84 (7) Å3
Triclinic, P1Z = 1
a = 7.8571 (4) ÅMo Kα
b = 8.3311 (6) ŵ = 1.22 mm−1
c = 8.9897 (7) ÅT = 293 (2) K
α = 89.8350 (11)º0.13 × 0.11 × 0.10 mm
β = 83.097 (1)º
Data collection top
Nonius MACH-3
diffractometer		1908 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)		Rint = 0.006
Tmin = 0.854, Tmax = 0.8862 standard reflections
2441 measured reflections every 60 min
1971 independent reflections intensity decay: none
Refinement top
R[F2 > 2σ(F2)] = 0.0314 restraints
wR(F2) = 0.087H atoms treated by a mixture of
independent and constrained refinement
S = 1.14Δρmax = 0.43 e Å−3
1971 reflectionsΔρmin = −0.71 e Å−3
196 parameters
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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Zn10.00000.50000.50000.02629 (14)
O1W0.2724 (2)0.4246 (2)0.4648 (2)0.0388 (4)
H1WA0.325 (5)0.498 (5)0.458 (4)0.058*
H1WB0.328 (5)0.351 (5)0.513 (4)0.058*
O2W−0.0055 (3)0.5054 (2)0.73549 (19)0.0421 (4)
H2WB0.085 (3)0.504 (5)0.774 (4)0.063*
H2WA−0.055 (5)0.439 (4)0.775 (4)0.063*
O3W−0.0111 (2)0.7546 (2)0.4830 (2)0.0404 (4)
H3WA0.014 (5)0.812 (4)0.549 (3)0.061*
H3WB−0.104 (3)0.817 (4)0.455 (4)0.061*
O10.6551 (2)−0.1387 (2)0.37983 (19)0.0378 (4)
O20.8538 (3)0.0707 (2)0.3227 (3)0.0595 (6)
O30.7109 (3)0.3187 (3)0.2651 (3)0.0595 (6)
O40.2551 (3)0.3894 (2)−0.0507 (2)0.0517 (5)
O50.0834 (3)0.2284 (3)−0.0310 (2)0.0547 (5)
O60.4083 (3)−0.3049 (3)0.3983 (2)0.0514 (5)
O70.2971 (3)−0.3042 (3)0.1909 (2)0.0571 (5)
N10.7226 (3)0.1697 (2)0.2785 (2)0.0353 (4)
N20.2129 (3)0.2680 (3)0.0013 (2)0.0380 (5)
N30.3679 (3)−0.2413 (3)0.2789 (2)0.0350 (4)
C10.5553 (3)−0.0462 (3)0.2971 (2)0.0265 (4)
C20.5767 (3)0.1112 (3)0.2393 (2)0.0275 (4)
C30.4649 (3)0.2134 (3)0.1486 (2)0.0303 (5)
H30.48330.31430.11780.036*
C40.3249 (3)0.1648 (3)0.1037 (2)0.0302 (5)
C50.2933 (3)0.0163 (3)0.1492 (2)0.0304 (5)
H50.1993−0.01540.11730.037*
C60.4035 (3)−0.0836 (3)0.2424 (2)0.0278 (4)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Zn10.0234 (2)0.0250 (2)0.0316 (2)−0.00531 (14)−0.01323 (14)0.00959 (13)
O1W0.0258 (8)0.0363 (9)0.0567 (11)−0.0088 (7)−0.0161 (7)0.0218 (8)
O2W0.0460 (11)0.0465 (10)0.0327 (9)−0.0074 (8)−0.0172 (8)0.0094 (7)
O3W0.0395 (10)0.0272 (9)0.0598 (11)−0.0089 (7)−0.0290 (8)0.0117 (8)
O10.0341 (9)0.0369 (9)0.0472 (10)−0.0110 (7)−0.0233 (7)0.0217 (7)
O20.0513 (12)0.0418 (11)0.0980 (16)−0.0184 (9)−0.0471 (11)0.0189 (10)
O30.0736 (14)0.0418 (11)0.0806 (15)−0.0325 (10)−0.0394 (12)0.0258 (10)
O40.0565 (12)0.0461 (11)0.0510 (11)−0.0064 (9)−0.0245 (9)0.0264 (9)
O50.0469 (11)0.0612 (12)0.0593 (12)−0.0097 (10)−0.0363 (10)0.0197 (10)
O60.0471 (11)0.0599 (12)0.0616 (12)−0.0293 (9)−0.0297 (9)0.0399 (10)
O70.0721 (14)0.0606 (13)0.0585 (12)−0.0428 (11)−0.0275 (11)0.0166 (10)
N10.0406 (11)0.0325 (10)0.0379 (10)−0.0134 (9)−0.0182 (9)0.0084 (8)
N20.0372 (11)0.0385 (11)0.0298 (10)0.0053 (9)−0.0136 (8)0.0075 (8)
N30.0278 (10)0.0398 (11)0.0412 (11)−0.0128 (8)−0.0119 (8)0.0136 (9)
C10.0245 (10)0.0266 (10)0.0260 (10)−0.0023 (8)−0.0079 (8)0.0063 (8)
C20.0292 (11)0.0272 (10)0.0267 (10)−0.0065 (9)−0.0105 (8)0.0047 (8)
C30.0359 (12)0.0257 (10)0.0262 (10)−0.0028 (9)−0.0083 (9)0.0058 (8)
C40.0292 (11)0.0316 (11)0.0244 (10)0.0022 (9)−0.0107 (8)0.0065 (8)
C50.0232 (10)0.0387 (12)0.0270 (10)−0.0034 (9)−0.0087 (8)0.0046 (9)
C60.0257 (10)0.0300 (11)0.0272 (10)−0.0062 (8)−0.0069 (8)0.0083 (8)
Geometric parameters (Å, °) top
Zn1—O1Wi2.0297 (16)O4—N21.228 (3)
Zn1—O1W2.0297 (16)O5—N21.224 (3)
Zn1—O3Wi2.1025 (16)O6—N31.230 (3)
Zn1—O3W2.1025 (16)O7—N31.221 (3)
Zn1—O2Wi2.1126 (17)N1—C21.451 (3)
Zn1—O2W2.1126 (17)N2—C41.451 (3)
O1W—H1WA0.83 (4)N3—C61.451 (3)
O1W—H1WB0.80 (4)C1—C21.456 (3)
O2W—H2WB0.822 (18)C1—C61.457 (3)
O2W—H2WA0.825 (18)C2—C31.374 (3)
O3W—H3WA0.837 (18)C3—C41.381 (3)
O3W—H3WB0.824 (19)C3—H30.93
O1—C11.242 (3)C4—C51.383 (3)
O2—N11.223 (3)C5—C61.374 (3)
O3—N11.224 (3)C5—H50.93
O1Wi—Zn1—O1W180.0O3—N1—C2118.43 (19)
O1Wi—Zn1—O3Wi92.05 (7)O5—N2—O4123.3 (2)
O1W—Zn1—O3Wi87.95 (7)O5—N2—C4118.6 (2)
O1Wi—Zn1—O3W87.95 (7)O4—N2—C4118.1 (2)
O1W—Zn1—O3W92.05 (7)O7—N3—O6122.8 (2)
O3Wi—Zn1—O3W180.0O7—N3—C6118.70 (19)
O1Wi—Zn1—O2Wi92.82 (8)O6—N3—C6118.5 (2)
O1W—Zn1—O2Wi87.18 (8)O1—C1—C2124.7 (2)
O3Wi—Zn1—O2Wi93.38 (8)O1—C1—C6124.1 (2)
O3W—Zn1—O2Wi86.62 (8)C2—C1—C6111.20 (18)
O1Wi—Zn1—O2W87.18 (8)C3—C2—N1115.76 (19)
O1W—Zn1—O2W92.82 (8)C3—C2—C1124.3 (2)
O3Wi—Zn1—O2W86.62 (8)N1—C2—C1119.89 (18)
O3W—Zn1—O2W93.38 (8)C2—C3—C4119.3 (2)
O2Wi—Zn1—O2W180.0C2—C3—H3120.3
Zn1—O1W—H1WA118 (2)C4—C3—H3120.3
Zn1—O1W—H1WB120 (3)C3—C4—C5121.54 (19)
H1WA—O1W—H1WB107 (3)C3—C4—N2119.3 (2)
Zn1—O2W—H2WB121 (3)C5—C4—N2119.1 (2)
Zn1—O2W—H2WA111 (3)C6—C5—C4118.8 (2)
H2WB—O2W—H2WA112 (4)C6—C5—H5120.6
Zn1—O3W—H3WA125 (3)C4—C5—H5120.6
Zn1—O3W—H3WB116 (2)C5—C6—N3115.6 (2)
H3WA—O3W—H3WB104 (3)C5—C6—C1124.8 (2)
O2—N1—O3121.6 (2)N3—C6—C1119.51 (18)
O2—N1—C2119.98 (19)
O2—N1—C2—C3−160.3 (2)O5—N2—C4—C56.7 (3)
O3—N1—C2—C319.3 (3)O4—N2—C4—C5−172.1 (2)
O2—N1—C2—C120.3 (3)C3—C4—C5—C60.6 (3)
O3—N1—C2—C1−160.1 (2)N2—C4—C5—C6177.90 (19)
O1—C1—C2—C3−179.5 (2)C4—C5—C6—N3−176.93 (19)
C6—C1—C2—C31.8 (3)C4—C5—C6—C1−0.7 (3)
O1—C1—C2—N1−0.2 (3)O7—N3—C6—C526.2 (3)
C6—C1—C2—N1−178.87 (19)O6—N3—C6—C5−152.9 (2)
N1—C2—C3—C4178.65 (19)O7—N3—C6—C1−150.2 (2)
C1—C2—C3—C4−2.0 (3)O6—N3—C6—C130.7 (3)
C2—C3—C4—C50.7 (3)O1—C1—C6—C5−179.1 (2)
C2—C3—C4—N2−176.59 (19)C2—C1—C6—C5−0.4 (3)
O5—N2—C4—C3−176.0 (2)O1—C1—C6—N3−3.0 (3)
O4—N2—C4—C35.2 (3)C2—C1—C6—N3175.65 (19)
Symmetry codes: (i) −x, −y+1, −z+1.
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O3W—H3WB···O1ii0.82 (2)2.02 (2)2.781 (2)153 (3)
O3W—H3WB···O2ii0.82 (2)2.38 (3)2.972 (3)130 (3)
O3W—H3WA···O2iii0.84 (2)2.07 (2)2.880 (3)164 (3)
O2W—H2WB···O3iii0.82 (2)2.48 (3)3.083 (3)131 (3)
O1W—H1WA···O6iv0.83 (4)1.99 (4)2.799 (3)164 (3)
O1W—H1WB···O1v0.80 (4)1.99 (4)2.705 (2)149 (3)
O1W—H1WB···O6v0.80 (4)2.24 (4)2.839 (2)132 (3)
O2W—H2WB···O4vi0.82 (2)2.22 (3)2.931 (3)144 (3)
O2W—H2WA···O5vi0.82 (2)2.57 (3)3.097 (3)123 (3)
O2W—H2WA···O7vii0.82 (2)2.46 (2)3.223 (3)154 (3)
Symmetry codes: (ii) x−1, y+1, z; (iii) −x+1, −y+1, −z+1; (iv) x, y+1, z; (v) −x+1, −y, −z+1; (vi) x, y, z+1; (vii) −x, −y, −z+1.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O3W—H3WB···O1i0.82 (2)2.02 (2)2.781 (2)153 (3)
O3W—H3WB···O2i0.82 (2)2.38 (3)2.972 (3)130 (3)
O3W—H3WA···O2ii0.84 (2)2.07 (2)2.880 (3)164 (3)
O2W—H2WB···O3ii0.82 (2)2.48 (3)3.083 (3)131 (3)
O1W—H1WA···O6iii0.83 (4)1.99 (4)2.799 (3)164 (3)
O1W—H1WB···O1iv0.80 (4)1.99 (4)2.705 (2)149 (3)
O1W—H1WB···O6iv0.80 (4)2.24 (4)2.839 (2)132 (3)
O2W—H2WB···O4v0.82 (2)2.22 (3)2.931 (3)144 (3)
O2W—H2WA···O5v0.82 (2)2.57 (3)3.097 (3)123 (3)
O2W—H2WA···O7vi0.82 (2)2.46 (2)3.223 (3)154 (3)
Symmetry codes: (i) x−1, y+1, z; (ii) −x+1, −y+1, −z+1; (iii) x, y+1, z; (iv) −x+1, −y, −z+1; (v) x, y, z+1; (vi) −x, −y, −z+1.
Acknowledgements top

The authors thank the UGC for the SAP programme and the DST for the FIST programme.

references
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