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Acta Cryst. (2008). E64, o665-o666    [ doi:10.1107/S1600536808005710 ]

Three-dimensional network in piperazine-1,4-diium-picrate-piperazine (1/2/1)

Z.-L. Wang and L.-H. Jia

Abstract top

In the title compound, C4H12N22+·2C6H2N3O7-·C4H10N2, the piperazine-1,4-diium cations and piperazine molecules lie on crystallographic inversion centres. In the crystal structure, intermolecular N-H...O and N-H...N hydrogen bonds link the components to form two-dimensional layers parallel to the (001) plane. These layers are, in turn, connected by weak intermolecular C-H...O hydrogen bonds and [pi]-[pi] stacking interactions [centroid-centroid distance between parallel aryl rings = 3.764 (2) Å, interplanar spacing = 3.500 (2) Å and ring offset = 1.387 (2) Å], forming a three-dimensional framework.

Comment top

Studies of picric acid (abbr. PA, pKa = 0.38) have been carried out for many years due to its formation of salts which involve electrostatic forces, multiple hydrogen bond modes (e.g. Hundal et al., 1997; Szumna et al., 2000) and π–π stacking interactions (Colquhoun et al., 1986) which can improve the quality of the crystalline materials. Recently, picrate anion containing molecular adducts have also been reported frequently in order to probe the competition between various intermolecular forces in crystal engineering (Anitha et al., 2006a, 2006b; Vembu et al., 2003; Ma et al., 2005; Akutagawa et al., 2003, Kavitha et al., 2005; Arnaud et al., 2007). As part of our study on molecular adducts involved with PA and piperazine (abbr. PP), we report here the molecular and supra-molecular structure of the title compound (I).

In (I), the asymmetric unit (atoms labelled without lower case suffixes in Fig.1) consists of one picrate anion, half a PA di-cation and half a neutral PA molecule. In the picrate anion, the nitro group at the 4-position is almost coplanar with the phenyl ring with a dihedral angle of only 4.1 (2)°, however, the nitro groups at the 2- and 6-positions are both significantly twisted out of the plane of the benzene ring, with dihedral angles of 45.2 (2)° and 21.7 (2)°, respectively. The rotations of the nitro groups at the 2- and 6- positions means that the picrate anion retains the approximate mirror symmetry which is also observed in the structure of a recently reported analog (Kavitha et al., 2006).

Analysis of the crystal packing of (I) shows that the component ions and molecules are linked into a simple three-dimensional network by a combination of N–H···O (or N), C–H···O hydrogen bonds and π–π stacking interactions which can be analyzed in terms of several substructures. First, by the co-operative hydrogen-bonding actions, i.e. bifurcated N4···O1(O7), bifurcated C8···O1(O2) and C7···O1 (-x, 2 - y, 1 - z) hydrogen bonds, the PA anions, PP di-cations and PP neutral molecules are linked into a one-dimensional tape structure parallel to the [110] direction generated by translation and inversion operations (Fig.2). Secondly, by a combinative actions of N5—H5A···O2 (x, 1 + y, z) and C2—H2···O6 (x, y - 1, z) hydrogen-bonds, the adjacent [110] 1-D tapes are joined together, forming a two-dimensional layer parallel to the (001) plane lying in domain of -0.299 < z < 1.299 (Fig.3). Finally, the neighbouring (001) layers are joined together by means of C9···O5 (-x + 1, -y + 3, -z + 2), C10···O4 (-x + 1, -y + 2, -z + 2) hydrogen bonds and π–π stacking interactions, which form the simple 3-D network. The geometry details of the π–π stacking interactions are as follows. The C1—C6 aryl rings of the anions at (x, y, z) and (1 - x, 2 - y, 2 - z) are strictly parallel, with an inter-planar spacing of 3.500 (2) Å; the ring-centroid separation is 3.764 (2) Å, corresponding to a ring offset of 1.387 (2) Å.

Related literature top

For related literature, see: Akutagawa et al. (2003); Allen et al. (1987); Anitha et al. (2006a,b); Arnaud et al. (2007); Colquhoun et al. (1986); Hundal et al. (1997); Kavitha et al. (2005, 2006); Ma et al. (2005); Szumna et al. (2000); Vembu et al. (2003).

Experimental top

All the reagents and solvents were used as obtained without further purification. 1:2 molar amount of anhydrous piperazine (0.2 mmol, 17.2 mg) and picric acid (0.4 mmol, 91.6 mg) were dissolved in 95% methanol (10 ml). The mixture was stirred for half an hour at ambient temperature and then filtered. The resulting yellow solution was kept in air for several days. Plate yellow crystals of (I) suitable for single-crystal X-ray diffraction analysis were grown by slow evaporation of the solution at the bottom of the vessel (yield: 45%, 56.7 mg, based on 2:1 organic salt; melting point: 512–514 K).

Refinement top

H atoms bonded to C atoms were placed in calculated positions with C–H=0.93Å (aromatic), 0.97Å (methylene) and Uiso(H) = 1.2Ueq(both aromatic and methylene C). H atoms attached to N atoms were located from the difference maps with the N–H distances being refined freely and Uiso(H) =1.2Ueq(N).

Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SMART (Bruker, 2001); data reduction: SAINT-Plus (Bruker, 2001); 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: PLATON (Spek, 2003).

Figures top
[Figure 1] Fig. 1. Molecular structure of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Inter-ion hydrogen bonds are shown as dashed lines, atoms marked with 'a', 'b' and 'c' are at symmetry positions (-x, 2 - y, 1 - z), (1 - x, 3 - y, 1 - z) and (-1 + x, -1 + y, z), respectively. An additional piperazine molecule is shown to illustrate the hydrogen bonding.
[Figure 2] Fig. 2. Part of the crystal structure of (I), showing the formation of the one-dimensional tape running parallel to the [110] direction. Hydrogen bonds are shown as dashed lines. For the sake of clarity, H atoms not involved in the motifs have been omitted. [symmetry code: (iii) -x, -y + 2, -z + 1]
[Figure 3] Fig. 3. Part of the crystal structure of (I), showing the linkage of adjacent 2-D layers by C9—H9A···O5, C10—H10A···O4 hydrogen bonds and π-π stacking interactions, which form the three-dimensional network. The green outlined area shows the 2-D layer parallel to the (001) plane. For the sake of clarity, H atoms not involved in the motifs have been omitted.
piperazine-1,4-diium–picrate–piperazine (1/2/1) top
Crystal data top
C4H12N22+·2C6H2N3O7–·C4H10N2Z = 1
Mr = 630.50F000 = 328
Triclinic, P1Dx = 1.612 Mg m−3
Hall symbol: -P 1Mo Kα radiation
λ = 0.71073 Å
a = 7.7150 (6) ÅCell parameters from 2518 reflections
b = 8.1658 (6) Åθ = 2.7–26.2º
c = 11.3024 (8) ŵ = 0.14 mm−1
α = 98.140 (1)ºT = 299 (2) K
β = 98.974 (1)ºPlate, yellow
γ = 109.250 (1)º0.20 × 0.10 × 0.06 mm
V = 649.62 (8) Å3
Data collection top
Bruker SMART APEX CCD area-detector
diffractometer		2258 independent reflections
Radiation source: fine focus sealed Siemens Mo tube1917 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.028
T = 299(2) Kθmax = 25.0º
0.3° wide ω exposures scansθmin = 2.7º
Absorption correction: multi-scan
(SADABS; Sheldrick, 1997)		h = −9→9
Tmin = 0.963, Tmax = 0.992k = −9→9
6131 measured reflectionsl = −13→13
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)] = 0.068H atoms treated by a mixture of
independent and constrained refinement
wR(F2) = 0.169  w = 1/[σ2(Fo2) + (0.0397P)2 + 1.340P]
where P = (Fo2 + 2Fc2)/3
S = 1.13(Δ/σ)max < 0.001
2258 reflectionsΔρmax = 0.27 e Å−3
208 parametersΔρmin = −0.27 e Å−3
Primary atom site location: structure-invariant direct methodsExtinction correction: none
Crystal data top
C4H12N22+·2C6H2N3O7–·C4H10N2γ = 109.250 (1)º
Mr = 630.50V = 649.62 (8) Å3
Triclinic, P1Z = 1
a = 7.7150 (6) ÅMo Kα
b = 8.1658 (6) ŵ = 0.14 mm−1
c = 11.3024 (8) ÅT = 299 (2) K
α = 98.140 (1)º0.20 × 0.10 × 0.06 mm
β = 98.974 (1)º
Data collection top
Bruker SMART APEX CCD area-detector
diffractometer		2258 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1997)		1917 reflections with I > 2σ(I)
Tmin = 0.963, Tmax = 0.992Rint = 0.028
6131 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.068208 parameters
wR(F2) = 0.169H atoms treated by a mixture of
independent and constrained refinement
S = 1.13Δρmax = 0.27 e Å−3
2258 reflectionsΔρmin = −0.27 e Å−3
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
C10.1576 (5)0.8052 (4)0.9002 (3)0.0332 (8)
C20.2353 (5)0.7965 (5)1.0152 (3)0.0378 (9)
H20.22960.68831.03480.045*
C30.3230 (5)0.9530 (5)1.1019 (3)0.0348 (8)
C40.3317 (5)1.1141 (5)1.0738 (3)0.0380 (9)
H40.39121.21811.13290.046*
C50.2518 (5)1.1200 (5)0.9578 (3)0.0371 (8)
C60.1526 (5)0.9660 (5)0.8609 (3)0.0333 (8)
C70.1883 (5)1.0168 (5)0.4896 (3)0.0392 (9)
H7A0.30731.00680.52260.047*
H7B0.19711.05700.41320.047*
C80.0332 (5)0.8378 (5)0.4654 (3)0.0381 (9)
H8A0.05490.75610.40340.046*
H8B0.03370.79120.53970.046*
C90.3474 (5)1.5596 (5)0.4793 (4)0.0405 (9)
H9A0.41241.68690.49380.049*
H9B0.21331.53520.45810.049*
C100.5940 (5)1.5299 (5)0.6247 (3)0.0386 (9)
H10A0.62101.48480.69760.046*
H10B0.66391.65660.64250.046*
N10.0732 (4)0.6390 (4)0.8092 (3)0.0405 (8)
N20.4143 (5)0.9504 (4)1.2226 (3)0.0443 (8)
N30.2705 (6)1.2965 (4)0.9349 (3)0.0528 (9)
N40.1521 (4)1.1476 (4)0.5768 (3)0.0364 (7)
H4A0.157 (6)1.118 (5)0.647 (4)0.044*
H4B0.228 (6)1.255 (6)0.584 (4)0.044*
N50.3922 (5)1.4953 (4)0.5905 (3)0.0383 (7)
H5A0.359 (6)1.548 (5)0.649 (4)0.046*
O10.0655 (4)0.9638 (4)0.7581 (2)0.0471 (7)
O20.1103 (5)0.6367 (4)0.7077 (3)0.0579 (8)
O3−0.0265 (5)0.5088 (4)0.8379 (3)0.0720 (10)
O40.4179 (6)0.8106 (4)1.2447 (3)0.0925 (14)
O50.4870 (5)1.0892 (4)1.2985 (3)0.0599 (9)
O60.3035 (6)1.4152 (4)1.0227 (3)0.0831 (12)
O70.2583 (6)1.3203 (4)0.8304 (3)0.0799 (12)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0349 (19)0.0294 (18)0.0331 (19)0.0089 (15)0.0063 (15)0.0074 (15)
C20.044 (2)0.0331 (19)0.036 (2)0.0137 (17)0.0052 (17)0.0123 (16)
C30.041 (2)0.039 (2)0.0265 (18)0.0153 (16)0.0073 (15)0.0104 (15)
C40.043 (2)0.0330 (19)0.037 (2)0.0147 (16)0.0079 (16)0.0037 (15)
C50.048 (2)0.034 (2)0.0346 (19)0.0204 (17)0.0097 (17)0.0113 (15)
C60.0357 (19)0.038 (2)0.0319 (19)0.0159 (16)0.0114 (16)0.0127 (15)
C70.0343 (19)0.041 (2)0.043 (2)0.0122 (16)0.0077 (16)0.0143 (17)
C80.045 (2)0.0317 (19)0.040 (2)0.0151 (16)0.0065 (17)0.0120 (16)
C90.035 (2)0.0284 (18)0.055 (2)0.0098 (15)0.0019 (17)0.0097 (17)
C100.047 (2)0.0268 (18)0.0346 (19)0.0065 (16)0.0011 (16)0.0090 (15)
N10.0443 (19)0.0374 (18)0.0353 (18)0.0124 (15)0.0026 (14)0.0059 (14)
N20.052 (2)0.0418 (19)0.0361 (18)0.0139 (16)0.0038 (15)0.0122 (15)
N30.081 (3)0.0366 (19)0.045 (2)0.0290 (18)0.0066 (18)0.0097 (16)
N40.0375 (17)0.0305 (16)0.0325 (17)0.0015 (13)0.0018 (13)0.0119 (13)
N50.0465 (19)0.0312 (16)0.0364 (17)0.0113 (14)0.0139 (14)0.0050 (13)
O10.0584 (17)0.0417 (15)0.0355 (15)0.0130 (13)−0.0024 (13)0.0163 (12)
O20.083 (2)0.0518 (18)0.0359 (16)0.0215 (16)0.0153 (15)0.0029 (13)
O30.082 (2)0.0404 (17)0.070 (2)−0.0071 (16)0.0138 (18)0.0096 (16)
O40.140 (4)0.0456 (19)0.063 (2)0.017 (2)−0.035 (2)0.0223 (17)
O50.082 (2)0.0534 (19)0.0335 (15)0.0252 (17)−0.0068 (15)−0.0042 (14)
O60.150 (4)0.0452 (19)0.061 (2)0.053 (2)0.010 (2)0.0046 (16)
O70.142 (4)0.0444 (19)0.049 (2)0.030 (2)0.005 (2)0.0194 (15)
Geometric parameters (Å, °) top
C1—C21.366 (5)C9—N51.465 (5)
C1—C61.454 (5)C9—C10ii1.504 (5)
C1—N11.461 (5)C9—H9A0.9700
C2—C31.385 (5)C9—H9B0.9700
C2—H20.9300C10—N51.465 (5)
C3—C41.380 (5)C10—C9ii1.504 (5)
C3—N21.441 (5)C10—H10A0.9700
C4—C51.373 (5)C10—H10B0.9700
C4—H40.9300N1—O31.210 (4)
C5—C61.442 (5)N1—O21.224 (4)
C5—N31.464 (5)N2—O41.210 (4)
C6—O11.243 (4)N2—O51.221 (4)
C7—N41.475 (5)N3—O61.215 (4)
C7—C81.508 (5)N3—O71.219 (4)
C7—H7A0.9700N4—C8i1.484 (5)
C7—H7B0.9700N4—H4A0.86 (4)
C8—N4i1.484 (5)N4—H4B0.86 (4)
C8—H8A0.9700N5—H5A0.86 (4)
C8—H8B0.9700
C2—C1—C6125.4 (3)N5—C9—C10ii110.2 (3)
C2—C1—N1117.1 (3)N5—C9—H9A109.6
C6—C1—N1117.5 (3)C10ii—C9—H9A109.6
C1—C2—C3118.3 (3)N5—C9—H9B109.6
C1—C2—H2120.8C10ii—C9—H9B109.6
C3—C2—H2120.8H9A—C9—H9B108.1
C4—C3—C2121.2 (3)N5—C10—C9ii109.1 (3)
C4—C3—N2118.7 (3)N5—C10—H10A109.9
C2—C3—N2120.0 (3)C9ii—C10—H10A109.9
C5—C4—C3119.5 (3)N5—C10—H10B109.9
C5—C4—H4120.2C9ii—C10—H10B109.9
C3—C4—H4120.2H10A—C10—H10B108.3
C4—C5—C6124.3 (3)O3—N1—O2122.7 (3)
C4—C5—N3116.0 (3)O3—N1—C1118.9 (3)
C6—C5—N3119.7 (3)O2—N1—C1118.3 (3)
O1—C6—C5126.4 (3)O4—N2—O5122.3 (3)
O1—C6—C1122.4 (3)O4—N2—C3118.7 (3)
C5—C6—C1111.1 (3)O5—N2—C3119.0 (3)
N4—C7—C8110.9 (3)O6—N3—O7122.6 (4)
N4—C7—H7A109.5O6—N3—C5117.9 (3)
C8—C7—H7A109.5O7—N3—C5119.5 (3)
N4—C7—H7B109.5C7—N4—C8i112.2 (3)
C8—C7—H7B109.5C7—N4—H4A109 (3)
H7A—C7—H7B108.0C8i—N4—H4A109 (3)
N4i—C8—C7110.4 (3)C7—N4—H4B114 (3)
N4i—C8—H8A109.6C8i—N4—H4B102 (3)
C7—C8—H8A109.6H4A—N4—H4B110 (4)
N4i—C8—H8B109.6C10—N5—C9110.9 (3)
C7—C8—H8B109.6C10—N5—H5A109 (3)
H8A—C8—H8B108.1C9—N5—H5A109 (3)
C6—C1—C2—C3−2.3 (6)N4—C7—C8—N4i55.1 (4)
N1—C1—C2—C3177.5 (3)C2—C1—N1—O344.6 (5)
C1—C2—C3—C40.2 (6)C6—C1—N1—O3−135.6 (4)
C1—C2—C3—N2−177.1 (3)C2—C1—N1—O2−133.7 (4)
C2—C3—C4—C50.2 (6)C6—C1—N1—O246.1 (5)
N2—C3—C4—C5177.5 (3)C4—C3—N2—O4−175.0 (4)
C3—C4—C5—C61.6 (6)C2—C3—N2—O42.4 (6)
C3—C4—C5—N3−178.8 (3)C4—C3—N2—O54.3 (5)
C4—C5—C6—O1173.8 (4)C2—C3—N2—O5−178.4 (4)
N3—C5—C6—O1−5.7 (6)C4—C5—N3—O6−20.6 (6)
C4—C5—C6—C1−3.2 (5)C6—C5—N3—O6159.0 (4)
N3—C5—C6—C1177.2 (3)C4—C5—N3—O7157.2 (4)
C2—C1—C6—O1−173.5 (4)C6—C5—N3—O7−23.2 (6)
N1—C1—C6—O16.7 (5)C8—C7—N4—C8i−56.1 (4)
C2—C1—C6—C53.7 (5)C9ii—C10—N5—C9−58.5 (4)
N1—C1—C6—C5−176.1 (3)C10ii—C9—N5—C1059.1 (4)
Symmetry codes: (i) −x, −y+2, −z+1; (ii) −x+1, −y+3, −z+1.
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N4—H4A···O10.86 (4)1.95 (4)2.745 (4)153 (4)
N4—H4A···O70.86 (4)2.31 (4)2.870 (5)123 (3)
N4—H4B···N50.86 (4)1.94 (4)2.799 (4)176 (4)
N5—H5A···O2iii0.86 (4)2.41 (4)3.153 (5)145 (4)
C2—H2···O6iv0.932.473.335 (5)155
C7—H7B···O1i0.972.523.211 (5)128
C8—H8B···O10.972.603.267 (5)127
C8—H8B···O20.972.523.458 (5)162
C9—H9A···O5v0.972.603.272 (5)127
C10—H10A···O4vi0.972.523.310 (5)138
Symmetry codes: (iii) x, y+1, z; (iv) x, y−1, z; (i) −x, −y+2, −z+1; (v) −x+1, −y+3, −z+2; (vi) −x+1, −y+2, −z+2.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N4—H4A···O10.86 (4)1.95 (4)2.745 (4)153 (4)
N4—H4A···O70.86 (4)2.31 (4)2.870 (5)123 (3)
N4—H4B···N50.86 (4)1.94 (4)2.799 (4)176 (4)
N5—H5A···O2i0.86 (4)2.41 (4)3.153 (5)145 (4)
C2—H2···O6ii0.932.473.335 (5)155
C7—H7B···O1iii0.972.523.211 (5)128
C8—H8B···O10.972.603.267 (5)127
C8—H8B···O20.972.523.458 (5)162
C9—H9A···O5iv0.972.603.272 (5)127
C10—H10A···O4v0.972.523.310 (5)138
Symmetry codes: (i) x, y+1, z; (ii) x, y−1, z; (iii) −x, −y+2, −z+1; (iv) −x+1, −y+3, −z+2; (v) −x+1, −y+2, −z+2.
Acknowledgements top

This work received financial support from the Hubei Province Key Fundamental Project.

references
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