



![[pi]](/logos/entities/pi_rmgif.gif)
![[pi]](/logos/entities/pi_rmgif.gif)
Supporting information
![]() | Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270110007134/sk3363sup1.cif |
![]() | Structure factor file (CIF format) https://doi.org/10.1107/S0108270110007134/sk3363Isup2.hkl |
CCDC reference: 774904
A suspension containing 3,5-dimethylpyrazole (0.192 g, 0.02 mmol) and H3PO4 (0.49 g, 5 mmol) in distilled water (30 ml) was stirred thoroughly for 30 min at ambient temperature. The suspension was transferred into a Teflon jacket in a stainless steel pressure vessel and kept in an oven at 433 K for 3 d under autogeneous pressure. The solution was then slowly cooled to ambient temperature to yield light-brown crystals of (I) suitable for X-ray diffraction analysis.
All H atoms were located in difference Fourier maps and treated as riding, with C—H = 0.96–0.97, N—H = 0.86 and O—H = 0.82 Å [Please check added text] and with Uiso(H) = 1.2Ueq(C,N) or 1.5Ueq(O). The isotropic displacement parameters for methyl H atoms were refined. The best crystal available was a thin plate (0.35 × 0.23 × 0.02 mm), which diffracted weakly at higher angles, so data collection was terminated at θ = 24.2°. Despite this, the title structure was refined using 99% of the possible data, which is considered adequate to give a precise structure.
Data collection: APEX2 (Bruker, 2007); cell refinement: APEX2 (Bruker, 2007) and SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007) and XPREP (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997), DIAMOND (Brandenburg, 1999) and Mercury (Macrae et al., 2006); software used to prepare material for publication: PLATON (Spek, 2009).
C11H17N4+·H2O4P− | Z = 2 |
Mr = 302.27 | F(000) = 320 |
Triclinic, P1 | Dx = 1.421 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 7.649 (4) Å | Cell parameters from 1408 reflections |
b = 10.504 (2) Å | θ = 2.3–24.2° |
c = 10.538 (2) Å | µ = 0.21 mm−1 |
α = 117.624 (3)° | T = 298 K |
β = 104.576 (4)° | Flake, brown |
γ = 94.663 (4)° | 0.35 × 0.23 × 0.02 mm |
V = 706.4 (5) Å3 |
Bruker APEXII Kappa CCD area-detector diffractometer | 2239 independent reflections |
Radiation source: fine-focus sealed tube | 1536 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.036 |
ω and ϕ scans | θmax = 24.2°, θmin = 2.3° |
Absorption correction: multi-scan (SADABS; Bruker, 2001) | h = −8→8 |
Tmin = 0.933, Tmax = 0.986 | k = −12→12 |
4686 measured reflections | l = −12→12 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.052 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.136 | H-atom parameters constrained |
S = 1.03 | w = 1/[σ2(Fo2) + (0.0706P)2 + 0.0452P] where P = (Fo2 + 2Fc2)/3 |
2239 reflections | (Δ/σ)max = 0.017 |
189 parameters | Δρmax = 0.20 e Å−3 |
0 restraints | Δρmin = −0.38 e Å−3 |
C11H17N4+·H2O4P− | γ = 94.663 (4)° |
Mr = 302.27 | V = 706.4 (5) Å3 |
Triclinic, P1 | Z = 2 |
a = 7.649 (4) Å | Mo Kα radiation |
b = 10.504 (2) Å | µ = 0.21 mm−1 |
c = 10.538 (2) Å | T = 298 K |
α = 117.624 (3)° | 0.35 × 0.23 × 0.02 mm |
β = 104.576 (4)° |
Bruker APEXII Kappa CCD area-detector diffractometer | 2239 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2001) | 1536 reflections with I > 2σ(I) |
Tmin = 0.933, Tmax = 0.986 | Rint = 0.036 |
4686 measured reflections |
R[F2 > 2σ(F2)] = 0.052 | 0 restraints |
wR(F2) = 0.136 | H-atom parameters constrained |
S = 1.03 | Δρmax = 0.20 e Å−3 |
2239 reflections | Δρmin = −0.38 e Å−3 |
189 parameters |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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. |
x | y | z | Uiso*/Ueq | ||
P1 | 0.39358 (13) | 0.05811 (10) | −0.31027 (10) | 0.0380 (3) | |
O1 | 0.3604 (3) | −0.0879 (2) | −0.4499 (3) | 0.0489 (7) | |
O2 | 0.4609 (3) | 0.0548 (3) | −0.1632 (2) | 0.0494 (7) | |
O3 | 0.5414 (4) | 0.1740 (3) | −0.3051 (3) | 0.0508 (7) | |
H3A | 0.5581 | 0.1402 | −0.3874 | 0.076* | |
O4 | 0.2154 (4) | 0.1154 (3) | −0.3088 (4) | 0.0644 (8) | |
H4 | 0.2244 | 0.1867 | −0.3215 | 0.097* | |
N1 | 0.0607 (4) | 0.6786 (3) | 0.3971 (3) | 0.0440 (8) | |
H1 | 0.1403 | 0.7620 | 0.4517 | 0.053* | |
N2 | 0.2495 (4) | 0.1435 (3) | 0.0302 (3) | 0.0435 (8) | |
H2 | 0.3054 | 0.1305 | −0.0347 | 0.052* | |
N3 | 0.2854 (4) | 0.0944 (3) | 0.1294 (3) | 0.0403 (7) | |
H3 | 0.3682 | 0.0459 | 0.1390 | 0.048* | |
N4 | −0.1193 (4) | 0.6618 (3) | 0.3240 (3) | 0.0415 (7) | |
C1 | 0.1130 (5) | 0.2159 (4) | 0.0482 (4) | 0.0415 (9) | |
C2 | 0.0441 (7) | 0.2893 (5) | −0.0399 (5) | 0.0702 (13) | |
H2A | 0.1072 | 0.3917 | 0.0169 | 0.123 (6)* | |
H2B | −0.0869 | 0.2810 | −0.0587 | 0.123 (6)* | |
H2C | 0.0677 | 0.2425 | −0.1347 | 0.123 (6)* | |
C3 | 0.1765 (6) | 0.1002 (5) | 0.3339 (4) | 0.0576 (11) | |
H3B | 0.2521 | 0.0304 | 0.3280 | 0.123 (6)* | |
H3C | 0.0531 | 0.0590 | 0.3226 | 0.123 (6)* | |
H3D | 0.2286 | 0.1893 | 0.4304 | 0.123 (6)* | |
C4 | 0.1696 (5) | 0.1342 (4) | 0.2109 (4) | 0.0372 (8) | |
C5 | 0.0586 (5) | 0.2114 (3) | 0.1613 (4) | 0.0355 (8) | |
C6 | −0.0901 (5) | 0.2780 (4) | 0.2208 (4) | 0.0439 (9) | |
H6A | −0.0971 | 0.2583 | 0.3009 | 0.053* | |
H6B | −0.2085 | 0.2293 | 0.1398 | 0.053* | |
C7 | −0.0611 (4) | 0.4416 (3) | 0.2815 (4) | 0.0339 (8) | |
C8 | −0.1938 (5) | 0.5165 (4) | 0.2529 (4) | 0.0370 (8) | |
C9 | −0.3950 (5) | 0.4581 (4) | 0.1581 (4) | 0.0592 (11) | |
H9A | −0.4536 | 0.5391 | 0.1735 | 0.123 (6)* | |
H9B | −0.4545 | 0.3966 | 0.1870 | 0.123 (6)* | |
H9C | −0.4059 | 0.4011 | 0.0530 | 0.123 (6)* | |
C10 | 0.1002 (5) | 0.5482 (4) | 0.3742 (4) | 0.0366 (8) | |
C11 | 0.2918 (5) | 0.5410 (4) | 0.4450 (4) | 0.0567 (11) | |
H11A | 0.3556 | 0.5111 | 0.3717 | 0.123 (6)* | |
H11B | 0.2849 | 0.4708 | 0.4788 | 0.123 (6)* | |
H11C | 0.3582 | 0.6366 | 0.5299 | 0.123 (6)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
P1 | 0.0406 (6) | 0.0362 (5) | 0.0415 (5) | 0.0136 (4) | 0.0207 (4) | 0.0186 (4) |
O1 | 0.0562 (17) | 0.0381 (14) | 0.0461 (14) | 0.0019 (12) | 0.0256 (12) | 0.0131 (12) |
O2 | 0.0602 (17) | 0.0654 (17) | 0.0408 (14) | 0.0311 (14) | 0.0271 (12) | 0.0329 (13) |
O3 | 0.0596 (17) | 0.0401 (14) | 0.0474 (15) | 0.0038 (12) | 0.0274 (13) | 0.0141 (12) |
O4 | 0.0576 (18) | 0.077 (2) | 0.109 (2) | 0.0405 (16) | 0.0518 (17) | 0.070 (2) |
N1 | 0.044 (2) | 0.0372 (18) | 0.0471 (17) | 0.0098 (14) | 0.0177 (15) | 0.0169 (15) |
N2 | 0.050 (2) | 0.0497 (19) | 0.0426 (17) | 0.0174 (15) | 0.0276 (15) | 0.0256 (15) |
N3 | 0.0435 (18) | 0.0400 (17) | 0.0440 (17) | 0.0192 (14) | 0.0207 (14) | 0.0215 (14) |
N4 | 0.0386 (19) | 0.0439 (18) | 0.0445 (17) | 0.0153 (14) | 0.0158 (14) | 0.0222 (15) |
C1 | 0.047 (2) | 0.040 (2) | 0.041 (2) | 0.0190 (18) | 0.0202 (17) | 0.0180 (17) |
C2 | 0.103 (4) | 0.081 (3) | 0.063 (3) | 0.053 (3) | 0.046 (3) | 0.051 (3) |
C3 | 0.066 (3) | 0.076 (3) | 0.064 (3) | 0.037 (2) | 0.038 (2) | 0.049 (2) |
C4 | 0.039 (2) | 0.0336 (19) | 0.0414 (19) | 0.0127 (16) | 0.0199 (17) | 0.0166 (16) |
C5 | 0.040 (2) | 0.0283 (18) | 0.0389 (19) | 0.0114 (16) | 0.0189 (16) | 0.0135 (15) |
C6 | 0.045 (2) | 0.041 (2) | 0.052 (2) | 0.0135 (17) | 0.0249 (18) | 0.0236 (18) |
C7 | 0.032 (2) | 0.0353 (19) | 0.0363 (18) | 0.0111 (16) | 0.0163 (15) | 0.0166 (16) |
C8 | 0.039 (2) | 0.036 (2) | 0.0353 (18) | 0.0122 (16) | 0.0153 (16) | 0.0149 (16) |
C9 | 0.047 (3) | 0.055 (2) | 0.064 (3) | 0.013 (2) | 0.008 (2) | 0.025 (2) |
C10 | 0.037 (2) | 0.042 (2) | 0.0372 (19) | 0.0189 (17) | 0.0196 (16) | 0.0203 (17) |
C11 | 0.042 (2) | 0.063 (3) | 0.063 (3) | 0.019 (2) | 0.0154 (19) | 0.030 (2) |
P1—O1 | 1.496 (2) | C3—C4 | 1.485 (5) |
P1—O2 | 1.523 (2) | C3—H3B | 0.9600 |
P1—O3 | 1.565 (2) | C3—H3C | 0.9600 |
P1—O4 | 1.535 (3) | C3—H3D | 0.9600 |
O3—H3A | 0.8200 | C4—C5 | 1.390 (5) |
O4—H4 | 0.8200 | C5—C6 | 1.502 (5) |
N1—N4 | 1.349 (4) | C6—C7 | 1.503 (5) |
N1—C10 | 1.350 (4) | C6—H6A | 0.9700 |
N1—H1 | 0.8600 | C6—H6B | 0.9700 |
N2—C1 | 1.341 (4) | C7—C10 | 1.373 (4) |
N2—N3 | 1.346 (4) | C7—C8 | 1.392 (5) |
N2—H2 | 0.8600 | C8—C9 | 1.500 (5) |
N3—C4 | 1.344 (4) | C9—H9A | 0.9600 |
N3—H3 | 0.8600 | C9—H9B | 0.9600 |
N4—C8 | 1.341 (4) | C9—H9C | 0.9600 |
C1—C5 | 1.377 (5) | C10—C11 | 1.493 (5) |
C1—C2 | 1.489 (5) | C11—H11A | 0.9600 |
C2—H2A | 0.9600 | C11—H11B | 0.9600 |
C2—H2B | 0.9600 | C11—H11C | 0.9600 |
C2—H2C | 0.9600 | ||
O1—P1—O2 | 114.01 (15) | N3—C4—C5 | 107.9 (3) |
O1—P1—O4 | 111.46 (17) | N3—C4—C3 | 122.0 (3) |
O2—P1—O4 | 105.64 (15) | C5—C4—C3 | 130.1 (3) |
O1—P1—O3 | 109.37 (13) | C1—C5—C4 | 106.5 (3) |
O2—P1—O3 | 108.22 (15) | C1—C5—C6 | 126.8 (3) |
O4—P1—O3 | 107.89 (16) | C4—C5—C6 | 126.6 (3) |
P1—O3—H3A | 109.5 | C5—C6—C7 | 114.5 (3) |
P1—O4—H4 | 109.5 | C5—C6—H6A | 108.6 |
N4—N1—C10 | 111.6 (3) | C7—C6—H6A | 108.6 |
N4—N1—H1 | 124.2 | C5—C6—H6B | 108.6 |
C10—N1—H1 | 124.2 | C7—C6—H6B | 108.6 |
C1—N2—N3 | 109.5 (3) | H6A—C6—H6B | 107.6 |
C1—N2—H2 | 125.2 | C10—C7—C8 | 105.4 (3) |
N3—N2—H2 | 125.2 | C10—C7—C6 | 127.9 (3) |
C4—N3—N2 | 108.3 (3) | C8—C7—C6 | 126.6 (3) |
C4—N3—H3 | 125.8 | N4—C8—C7 | 110.7 (3) |
N2—N3—H3 | 125.8 | N4—C8—C9 | 119.5 (3) |
C8—N4—N1 | 105.2 (3) | C7—C8—C9 | 129.8 (3) |
N2—C1—C5 | 107.7 (3) | C8—C9—H9A | 109.5 |
N2—C1—C2 | 123.4 (3) | C8—C9—H9B | 109.5 |
C5—C1—C2 | 128.9 (3) | H9A—C9—H9B | 109.5 |
C1—C2—H2A | 109.5 | C8—C9—H9C | 109.5 |
C1—C2—H2B | 109.5 | H9A—C9—H9C | 109.5 |
H2A—C2—H2B | 109.5 | H9B—C9—H9C | 109.5 |
C1—C2—H2C | 109.5 | N1—C10—C7 | 107.0 (3) |
H2A—C2—H2C | 109.5 | N1—C10—C11 | 120.7 (3) |
H2B—C2—H2C | 109.5 | C7—C10—C11 | 132.3 (3) |
C4—C3—H3B | 109.5 | C10—C11—H11A | 109.5 |
C4—C3—H3C | 109.5 | C10—C11—H11B | 109.5 |
H3B—C3—H3C | 109.5 | H11A—C11—H11B | 109.5 |
C4—C3—H3D | 109.5 | C10—C11—H11C | 109.5 |
H3B—C3—H3D | 109.5 | H11A—C11—H11C | 109.5 |
H3C—C3—H3D | 109.5 | H11B—C11—H11C | 109.5 |
C1—N2—N3—C4 | 0.7 (4) | C4—C5—C6—C7 | 121.5 (4) |
C10—N1—N4—C8 | −0.3 (4) | C5—C6—C7—C10 | −44.3 (5) |
N3—N2—C1—C5 | −0.7 (4) | C5—C6—C7—C8 | 134.6 (4) |
N3—N2—C1—C2 | 177.6 (3) | N1—N4—C8—C7 | 0.2 (4) |
N2—N3—C4—C5 | −0.3 (4) | N1—N4—C8—C9 | −179.4 (3) |
N2—N3—C4—C3 | −178.3 (3) | C10—C7—C8—N4 | −0.1 (4) |
N2—C1—C5—C4 | 0.5 (4) | C6—C7—C8—N4 | −179.2 (3) |
C2—C1—C5—C4 | −177.7 (4) | C10—C7—C8—C9 | 179.5 (3) |
N2—C1—C5—C6 | 179.9 (3) | C6—C7—C8—C9 | 0.4 (6) |
C2—C1—C5—C6 | 1.7 (6) | N4—N1—C10—C7 | 0.2 (4) |
N3—C4—C5—C1 | −0.1 (4) | N4—N1—C10—C11 | −179.9 (3) |
C3—C4—C5—C1 | 177.7 (4) | C8—C7—C10—N1 | 0.0 (4) |
N3—C4—C5—C6 | −179.5 (3) | C6—C7—C10—N1 | 179.1 (3) |
C3—C4—C5—C6 | −1.8 (6) | C8—C7—C10—C11 | −180.0 (4) |
C1—C5—C6—C7 | −57.8 (5) | C6—C7—C10—C11 | −0.9 (6) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O1i | 0.86 | 1.89 | 2.726 (4) | 164 |
N2—H2···O2 | 0.86 | 1.96 | 2.789 (4) | 161 |
N3—H3···O2ii | 0.86 | 1.79 | 2.649 (4) | 178 |
O3—H3A···O1iii | 0.82 | 1.83 | 2.639 (3) | 169 |
O4—H4···N4iv | 0.82 | 1.85 | 2.571 (4) | 146 |
Symmetry codes: (i) x, y+1, z+1; (ii) −x+1, −y, −z; (iii) −x+1, −y, −z−1; (iv) −x, −y+1, −z. |
Experimental details
Crystal data | |
Chemical formula | C11H17N4+·H2O4P− |
Mr | 302.27 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 298 |
a, b, c (Å) | 7.649 (4), 10.504 (2), 10.538 (2) |
α, β, γ (°) | 117.624 (3), 104.576 (4), 94.663 (4) |
V (Å3) | 706.4 (5) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.21 |
Crystal size (mm) | 0.35 × 0.23 × 0.02 |
Data collection | |
Diffractometer | Bruker APEXII Kappa CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2001) |
Tmin, Tmax | 0.933, 0.986 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 4686, 2239, 1536 |
Rint | 0.036 |
(sin θ/λ)max (Å−1) | 0.576 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.052, 0.136, 1.03 |
No. of reflections | 2239 |
No. of parameters | 189 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.20, −0.38 |
Computer programs: , APEX2 (Bruker, 2007) and SAINT (Bruker, 2007), SAINT (Bruker, 2007) and XPREP (Bruker, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997), DIAMOND (Brandenburg, 1999) and Mercury (Macrae et al., 2006), PLATON (Spek, 2009).
P1—O1 | 1.496 (2) | N1—C10 | 1.350 (4) |
P1—O2 | 1.523 (2) | N2—C1 | 1.341 (4) |
P1—O3 | 1.565 (2) | N2—N3 | 1.346 (4) |
P1—O4 | 1.535 (3) | N3—C4 | 1.344 (4) |
N1—N4 | 1.349 (4) | N4—C8 | 1.341 (4) |
C1—C5—C6—C7 | −57.8 (5) | C5—C6—C7—C10 | −44.3 (5) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O1i | 0.86 | 1.89 | 2.726 (4) | 164.0 |
N2—H2···O2 | 0.86 | 1.96 | 2.789 (4) | 161.3 |
N3—H3···O2ii | 0.86 | 1.79 | 2.649 (4) | 178.4 |
O3—H3A···O1iii | 0.82 | 1.83 | 2.639 (3) | 169.0 |
O4—H4···N4iv | 0.82 | 1.85 | 2.571 (4) | 146.3 |
Symmetry codes: (i) x, y+1, z+1; (ii) −x+1, −y, −z; (iii) −x+1, −y, −z−1; (iv) −x, −y+1, −z. |
Atom | Charge | Atom | Charge |
P1 | 1.435 | C1 | 0.173 |
N1 | -0.152 | C2 | -0.263 |
N2 | -0.118 | C3 | -0.250 |
N3 | -0.149 | C4 | 0.178 |
N4 | -0.244 | C5 | -0.006 |
O1 | -0.741 | C6 | -0.230 |
O2 | -0.821 | C7 | -0.036 |
O3 | -0.623 | C8 | 0.101 |
O4 | -0.630 | C9 | -0.231 |
C10 | 0.145 | C11 | -0.253 |
Dipole (a.u.) | 5.58976 | ||
Ebinding (eV) | -173.12 | ||
EHOMO (eV) | -3.791 | ELUMO (eV) | -2.453 |
Hybrid organic–inorganic adducts are of current interest due to their intriguing architectures and potential applications in crystal engineering (Ma et al., 2009; Almeida Paz et al., 2004). The intermolecular forces between the different components of these hybrid crystals are provided by hydrogen-bonding or other non-covalent and non-ionic interactions (Almarsson & Zaworotko, 2004). Among the various compounds available for studying phosphoric acid–ligand interactions, amines and N-unsubstituted pyrazoles possessing one or more active lone pairs have been frequently used (Turki et al., 2006; Elaoud et al., 2000). The strong N—H···O hydrogen bonds and possible π–π stacking in these hybrid systems facilitate molecular assemblies with one-dimensional chains, two-dimensional layers or three-dimensional frameworks (Turner & Batten, 2008; Oueslati et al., 2006). The recurring structural ensembles in these structures, referred to as synthons (Desiraju, 1995), have been used as building blocks for designing new crystalline materials. Several monophosphate ion–organic ligand hybrid systems also display interesting physical properties, such as ferroelectricity, piezoelectricity and nonlinear optical phenomena (Masse et al., 1993).
The asymmetric unit of (I) consists of a 4-(3,5-dimethyl-1H-pyrazol-4-ylmethyl)-3,5-dimethyl-1H-pyrazol-2-ium (mdmp) cation and a dihydrogen phosphate counteranion (Fig. 1). The molecular conformation of the mdmp cation can be defined in terms of two torsion angles, C2—C3—C10—C5 = -44.3 (5)° and C3—C10—C5—C1 = -57.8 (5)°. The two pyrazole rings (A and B) are essentially planar, with r.m.s. fits of the atomic positions of 0.001 Å for ring A and 0.003 Å for ring B. The twist about the methylene bridge in the mdmp+ cation is reflected by the dihedral angle of 82.2 (2)° between the pyrazole rings; the corresponding value in a crystal of mdmp without any phosphate counterion is 81.7 (2)°. The deviation of the A/B dihedral angle in (I) [82.2 (2)°] from that observed in 4,4'-methylenebispyrazole [90.3 (1)°; Monge et al., 1994], in which both the pyrazole rings are unsubstituted, is probably due to non-bonding interactions between the methyl groups and the H atoms of the methylene bridge.
The N—N bond length in the pyrazole ring varies over a wide range, 1.234 (8)–1.385 (4) Å, depending on the substituents at the N atoms (Kettmann & Světlík, 2002). Accordingly, the adjacent C—N distances range from 1.288 (4) to 1.461 (8) Å. The conjugation within the π-electron system of the pyrazole rings in (I) is reflected in the N—N [1.346 (4)–1.349 (4) Å] and C—N [1.341 (4)–1.350 (4) Å] bond lengths (Table 1), which are intermediate between a single and a double bond, and agree with those reported in the literature (Monge et al., 1994; Masse & Tordjman, 1990). The P—O [1.496 (2)–1.523 (2) Å] and P—OH [1.535 (3)–1.565 (2) Å] bond distances in (I) are comparable with the reported values for related phosphates (Oueslati et al., 2006; Turki et al., 2006; Smirani et al., 2004).
As often observed in this kind of system, the two components of (I), i.e. the mdmp+ and H2PO4- ions, are connected through a network of hydrogen bonds and aromatic π–π stacking, in which both pyrazole rings participate (Table 2). It is convenient to consider the substructures generated by different kinds of hydrogen bond acting individually, and then a combination of substructures to build a supramolecular assembly.
Centrosymmetrically related phosphate tetrahedra are connected through pairs of O3—H(O3)···O1 hydrogen bonds, which according to graph-set notation (Bernstein et al., 1995) can be described as an R22(8) ring centred at (1/2, 0, 1/2). Intermolecular N1—H(N1)···O1(x, 1 + y, 1 + z) and N2—H(N2)···O2(x, y, z) hydrogen bonds link the mdmp+ cation and phosphate anion into a polymeric C(13) chain propagating along the [001] direction, as shown in Fig. 2. Similarly, another C(13) chain running along the [010] direction is formed by intermolecular N3—H(N3)···O2(1 - x, -y, -z) and O4—H(O4)···N4(-x, 1 - y, -z) hydrogen bonds. The interactions mentioned above generate two types of supramolecular arrangement. In the first, two phosphate anions at (x, y, z) and (1 - x, -y, -z), together with the pyrazole B rings of mdmp+ cations at (1 - x, -y, -z) and (x, y, z), give rise to the formation of a cyclic R44(10) synthon having its symmetry centre at (1/2, 0, 0) (Fig. 3). The second R44(14) synthon (Fig. 3) is formed by two H2PO4- anions at (x, y, z) and (-x, -y, -1 - z) and two pyrazole A rings of cations at (-x, 1 - y, -z) and (x, y - 1, z - 1), with a symmetry centre at (0, 0, -1/2). Propagation of the R44(10) and R44(14) rings through lattice translations generates an R44(24) synthon centred at (0, 1/2, 0), which in combination with other R44(X) rings forms a three-dimensional molecular framework. Viewed down (111), the three-dimensional network appears as a honeycomb structure with fused R44(X) rings (Fig. 3).
The molecular packing in (I) facilitates π–π interactions. The pyrazole B rings of centrosymmetrically related mdmp+ cations form a π–π stacking interaction across the inversion centre at (0, 0, 0); the interplanar spacing and centroid separation are 3.447 and 3.474 (3) Å, respectively, corresponding to a centroid offset of 0.432 Å. Similarly, the pyrazole A rings in the cations at (x, y, z) and (-x, 1 - y, 1 - z) form a second π–π stacking interaction across the inversion centre at (0, 1/2, 1/2), where the interplanar spacing and centroid separation are 3.586 and 4.462 (3) Å, respectively, corresponding to a centroid offset of 2.656 Å.
Solid-state density functional theory (DFT) calculations of (I) have been performed using the DMOL3 code (Delly, 1996, 1998) in the framework of a generalized-gradient approximation (GGA) (Perdew et al., 1996). The starting atomic coordinates were taken from the final X-ray refinement cycle. The geometry of the system was fully optimized using the hybrid exchange-correlation function BLYP (Becke, 1988; Lee et al., 1988) and a double numeric plus polarization (DNP) basis set. The cell parameters were kept fixed during the DFT calculations. No constraints were applied to bond lengths, bond angles or dihedral angles during the calculations, and all atoms were free to optimize.
A superposition of molecular conformations of (I), as established by the X-ray study and quantum mechanical calculations, shows good agreement (Fig. 4); the r.m.s. deviation between the coordinates obtained by geometry optimization and X-ray structure analysis is 0.025 Å. The net charges of atoms and dipoles, and the molecular orbital energy of (I) calculated at the BLYP level are listed in Table 3. The O and N atoms in (I) bear negative charges, while atom P1 bears a positive charge. The C atoms of the pyrazole rings with methyl substituents (C1, C2, C4 and C6) bear positive charges, while the bridging C (C10) and methyl C (C7, C8, C9 and C11) atoms bear negative charges. The bridge-head C atoms of ring A (C3) and ring B (C5) are almost neutral. The orbital energy level analysis for (I) at the BLYP level shows EHOMO (highest occupied molecular orbital) and ELUMO (lowest unoccupied molecular orbital) values of -3.791 and -2.453 eV, respectively. The HOMO–LUMO energy separation has been used as a simple indicator of kinetic stability (Aihara, 1999; Kim et al., 2005). The small HOMO–LUMO gap in (I) (1.338 eV) probably indicates a high chemical reactivity for the title compound. The charge densities for the HOMO and LUMO are shown in Fig. 5.