Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536805041103/fl6198sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536805041103/fl6198Isup2.hkl |
CCDC reference: 296561
Several approaches have been used for the synthesis of VOPO4·2H2O, the starting material in this study. The conventional approach involves the prolonged refluxing of V2O5 in aqueous phosphoric acid (Ladwig, 1965). A more rapid method uses a sonochemical approach (Park et al., 2001). In order to optimize the possible reactions, we decided to make a highly porous phosphate of formula VOPO4·2H2O by reacting foam gel V2O5 (Chandrappa et al., 2002) with phosphoric acid. The title compound was isolated from a mixture of excess imidazole and the above VOPO4·2H2O in a 3:1 molar ratio. This mixture was allowed to stand for 30 d under ambient conditions. Crystals began to grow at the surface of a greenish solid precipitate in the beaker. The title compound was obtained by careful removal of a single-crystal from the mixture.
H atoms of the phosphate groups were located from a difference Fourier map and refined independently. On introducing partially occupied H atoms into the PO4 groups, refinement of the H-atom positions was constrained, but the Uiso(H) values were refined freely. The H atoms of the imidazolium ions were refined within a rigid-body model riding on their parent C or N atoms, with C—H = 0.93 Å and N—H = 0.86 Å, and with Uiso(H) = 1.2Ueq(C,N). [Please check added text]
Data collection: SMART (Bruker, 1999); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97.
H3PO4·C3H5N2+·H2PO4− | F(000) = 544 |
Mr = 264.07 | Dx = 1.749 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 3640 reflections |
a = 9.138 (4) Å | θ = 2.6–31.3° |
b = 14.605 (6) Å | µ = 0.46 mm−1 |
c = 7.516 (3) Å | T = 296 K |
β = 91.447 (6)° | Prism, colourless |
V = 1002.8 (7) Å3 | 0.36 × 0.28 × 0.24 mm |
Z = 4 |
Bruker APEX CCD area-detector diffractometer | 2291 independent reflections |
Radiation source: fine-focus sealed tube | 1895 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.025 |
Detector resolution: 8.33 pixels mm-1 | θmax = 27.5°, θmin = 2.2° |
ω scans | h = −11→8 |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | k = −16→18 |
Tmin = 0.802, Tmax = 0.895 | l = −9→9 |
6101 measured reflections |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.038 | H-atom parameters constrained |
wR(F2) = 0.079 | w = 1/[σ2(Fo2) + (0.003P)2 + 1.182P] where P = [-max(Fo2,0) + 2Fc2]/3 |
S = 1.00 | (Δ/σ)max < 0.001 |
2291 reflections | Δρmax = 0.28 e Å−3 |
162 parameters | Δρmin = −0.36 e Å−3 |
40 restraints | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0192 (9) |
H3PO4·C3H5N2+·H2PO4− | V = 1002.8 (7) Å3 |
Mr = 264.07 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 9.138 (4) Å | µ = 0.46 mm−1 |
b = 14.605 (6) Å | T = 296 K |
c = 7.516 (3) Å | 0.36 × 0.28 × 0.24 mm |
β = 91.447 (6)° |
Bruker APEX CCD area-detector diffractometer | 2291 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 1895 reflections with I > 2σ(I) |
Tmin = 0.802, Tmax = 0.895 | Rint = 0.025 |
6101 measured reflections |
R[F2 > 2σ(F2)] = 0.038 | 40 restraints |
wR(F2) = 0.079 | H-atom parameters constrained |
S = 1.00 | Δρmax = 0.28 e Å−3 |
2291 reflections | Δρmin = −0.36 e Å−3 |
162 parameters |
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. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
N1 | 0.1910 (4) | −0.0147 (3) | 0.6095 (6) | 0.0482 (12) | 0.775 (5) |
H1 | 0.1425 | −0.0293 | 0.7019 | 0.058* | 0.775 (5) |
C2 | 0.2814 (6) | 0.0540 (3) | 0.5987 (6) | 0.0496 (11) | 0.775 (5) |
H2 | 0.3060 | 0.0947 | 0.6899 | 0.059* | 0.775 (5) |
N3 | 0.3314 (4) | 0.0557 (3) | 0.4369 (6) | 0.0530 (11) | 0.775 (5) |
H3 | 0.3925 | 0.0948 | 0.3963 | 0.064* | 0.775 (5) |
C4 | 0.2694 (7) | −0.0156 (5) | 0.3435 (7) | 0.0698 (17) | 0.775 (5) |
H4 | 0.2844 | −0.0299 | 0.2248 | 0.084* | 0.775 (5) |
C5 | 0.1858 (6) | −0.0593 (3) | 0.4521 (8) | 0.0580 (12) | 0.775 (5) |
H5 | 0.1321 | −0.1118 | 0.4260 | 0.070* | 0.775 (5) |
N1A | 0.3153 (16) | 0.0060 (13) | 0.362 (2) | 0.0482 (12) | 0.225 (5) |
H1A | 0.3587 | 0.0205 | 0.2663 | 0.058* | 0.225 (5) |
C2A | 0.311 (2) | 0.0571 (13) | 0.516 (4) | 0.0580 (12) | 0.225 (5) |
H2A | 0.3574 | 0.1124 | 0.5406 | 0.070* | 0.225 (5) |
N3A | 0.226 (3) | 0.0103 (17) | 0.617 (3) | 0.0698 (17) | 0.225 (5) |
H3A | 0.2038 | 0.0251 | 0.7234 | 0.084* | 0.225 (5) |
C4A | 0.179 (2) | −0.0629 (15) | 0.533 (3) | 0.0530 (11) | 0.225 (5) |
H4A | 0.1091 | −0.1034 | 0.5744 | 0.064* | 0.225 (5) |
C5A | 0.241 (2) | −0.0697 (12) | 0.391 (2) | 0.0496 (11) | 0.225 (5) |
H5A | 0.2357 | −0.1201 | 0.3153 | 0.059* | 0.225 (5) |
P1 | 0.01161 (6) | 0.16289 (3) | 0.03493 (7) | 0.02685 (15) | |
O11 | 0.06306 (18) | 0.15451 (10) | −0.15976 (19) | 0.0386 (4) | |
H11 | 0.0805 | 0.2056 | −0.1990 | 0.036 (9)* | 0.70 (4) |
O12 | −0.11891 (17) | 0.22935 (11) | 0.0439 (2) | 0.0476 (4) | |
H12 | −0.1893 | 0.2077 | −0.0114 | 0.074 (11)* | |
O13 | 0.12885 (16) | 0.20326 (11) | 0.1534 (2) | 0.0355 (4) | |
H13 | 0.0916 | 0.2374 | 0.2261 | 0.036 (9)* | 0.30 (4) |
O14 | −0.03690 (19) | 0.06759 (10) | 0.0857 (2) | 0.0446 (4) | |
H14 | 0.0001 | 0.0301 | 0.0192 | 0.055 (17)* | 0.50 |
P2 | 0.50326 (6) | 0.16567 (4) | 0.03353 (7) | 0.02883 (15) | |
O21 | 0.55744 (18) | 0.15440 (11) | 0.2303 (2) | 0.0398 (4) | |
H21 | 0.5776 | 0.2048 | 0.2722 | 0.056 (9)* | |
O22 | 0.37996 (17) | 0.23818 (11) | 0.0257 (2) | 0.0412 (4) | |
H22 | 0.3072 | 0.2179 | 0.0738 | 0.084 (12)* | |
O23 | 0.62265 (16) | 0.20105 (11) | −0.0815 (2) | 0.0386 (4) | |
O24 | 0.43963 (19) | 0.07395 (11) | −0.0202 (2) | 0.0475 (4) | |
H24 | 0.5002 | 0.0336 | 0.0002 | 0.056 (18)* | 0.50 |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.044 (2) | 0.058 (3) | 0.0428 (17) | −0.0056 (16) | 0.0130 (15) | 0.0116 (19) |
C2 | 0.058 (2) | 0.051 (2) | 0.0405 (18) | −0.0082 (17) | 0.0060 (16) | −0.0091 (17) |
N3 | 0.062 (2) | 0.055 (2) | 0.0429 (19) | −0.0234 (15) | 0.0087 (15) | 0.0090 (17) |
C4 | 0.079 (4) | 0.087 (4) | 0.044 (2) | −0.025 (3) | 0.018 (2) | −0.024 (2) |
C5 | 0.067 (3) | 0.0396 (19) | 0.068 (3) | −0.0160 (17) | 0.007 (3) | −0.007 (2) |
N1A | 0.044 (2) | 0.058 (3) | 0.0428 (17) | −0.0056 (16) | 0.0130 (15) | 0.0116 (19) |
C2A | 0.067 (3) | 0.0396 (19) | 0.068 (3) | −0.0160 (17) | 0.007 (3) | −0.007 (2) |
N3A | 0.079 (4) | 0.087 (4) | 0.044 (2) | −0.025 (3) | 0.018 (2) | −0.024 (2) |
C4A | 0.062 (2) | 0.055 (2) | 0.0429 (19) | −0.0234 (15) | 0.0087 (15) | 0.0090 (17) |
C5A | 0.058 (2) | 0.051 (2) | 0.0405 (18) | −0.0082 (17) | 0.0060 (16) | −0.0091 (17) |
P1 | 0.0265 (3) | 0.0219 (3) | 0.0323 (3) | −0.0002 (2) | 0.0049 (2) | −0.0022 (2) |
O11 | 0.0562 (10) | 0.0293 (8) | 0.0306 (8) | −0.0045 (7) | 0.0063 (7) | 0.0009 (6) |
O12 | 0.0279 (8) | 0.0365 (9) | 0.0779 (12) | 0.0062 (7) | −0.0074 (8) | −0.0179 (8) |
O13 | 0.0270 (8) | 0.0414 (9) | 0.0382 (8) | 0.0037 (7) | 0.0021 (6) | −0.0102 (7) |
O14 | 0.0619 (11) | 0.0266 (8) | 0.0463 (9) | −0.0061 (8) | 0.0240 (8) | −0.0009 (7) |
P2 | 0.0243 (3) | 0.0273 (3) | 0.0349 (3) | 0.0023 (2) | 0.0015 (2) | −0.0013 (2) |
O21 | 0.0483 (10) | 0.0353 (9) | 0.0358 (8) | −0.0007 (7) | 0.0000 (7) | 0.0004 (7) |
O22 | 0.0276 (8) | 0.0324 (8) | 0.0638 (11) | 0.0055 (7) | 0.0090 (7) | 0.0072 (7) |
O23 | 0.0247 (7) | 0.0526 (10) | 0.0386 (8) | 0.0039 (7) | 0.0037 (6) | 0.0047 (7) |
O24 | 0.0438 (10) | 0.0326 (9) | 0.0655 (11) | −0.0007 (8) | −0.0102 (8) | −0.0090 (8) |
N1—C2 | 1.303 (5) | C5—H5 | 0.9300 |
N1—C5 | 1.351 (6) | P1—O13 | 1.4965 (16) |
N1—H1 | 0.8600 | P1—O14 | 1.5125 (16) |
C2—N3 | 1.311 (4) | P1—O12 | 1.5405 (16) |
C2—H2 | 0.9300 | P1—O11 | 1.5530 (16) |
N3—C4 | 1.369 (6) | P2—O23 | 1.5010 (16) |
N3—H3 | 0.8600 | P2—O24 | 1.5112 (17) |
C4—C5 | 1.299 (7) | P2—O22 | 1.5464 (16) |
C4—H4 | 0.9300 | P2—O21 | 1.5565 (17) |
C2—N1—C5 | 109.0 (3) | O13—P1—O11 | 111.24 (9) |
C2—N1—H1 | 125.5 | O14—P1—O11 | 105.22 (9) |
C5—N1—H1 | 125.5 | O12—P1—O11 | 110.11 (10) |
N1—C2—N3 | 108.0 (3) | P1—O11—H11 | 109.5 |
N1—C2—H2 | 126.0 | P1—O12—H12 | 109.5 |
N3—C2—H2 | 126.0 | P1—O13—H13 | 109.5 |
C2—N3—C4 | 108.2 (3) | P1—O14—H14 | 109.5 |
C2—N3—H3 | 125.9 | O23—P2—O24 | 115.57 (10) |
C4—N3—H3 | 125.9 | O23—P2—O22 | 106.37 (9) |
C5—C4—N3 | 107.1 (4) | O24—P2—O22 | 108.77 (10) |
C5—C4—H4 | 126.5 | O23—P2—O21 | 111.44 (9) |
N3—C4—H4 | 126.5 | O24—P2—O21 | 105.72 (10) |
C4—C5—N1 | 107.8 (4) | O22—P2—O21 | 108.82 (9) |
C4—C5—H5 | 126.1 | P2—O21—H21 | 109.5 |
O13—P1—O14 | 115.00 (10) | P2—O22—H22 | 109.5 |
O13—P1—O12 | 105.62 (9) | P2—O24—H24 | 109.5 |
O14—P1—O12 | 109.67 (10) | ||
C5—N1—C2—N3 | 1.5 (5) | N3—C4—C5—N1 | 2.0 (7) |
N1—C2—N3—C4 | −0.3 (5) | C2—N1—C5—C4 | −2.2 (6) |
C2—N3—C4—C5 | −1.1 (6) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O14i | 0.86 | 1.97 | 2.827 (4) | 177 |
N3—H3···O21 | 0.86 | 2.16 | 2.986 (4) | 160 |
O11—H11···O13ii | 0.82 | 1.79 | 2.587 (2) | 162 |
O12—H12···O23iii | 0.82 | 1.79 | 2.554 (2) | 155 |
O13—H13···O11iv | 0.82 | 1.82 | 2.587 (2) | 155 |
O14—H14···O14v | 0.82 | 1.67 | 2.461 (3) | 162 |
O21—H21···O23iv | 0.82 | 1.80 | 2.602 (2) | 165 |
O22—H22···O13 | 0.82 | 1.76 | 2.561 (2) | 164 |
O24—H24···O24vi | 0.82 | 1.67 | 2.441 (4) | 156 |
Symmetry codes: (i) −x, −y, −z+1; (ii) x, −y+1/2, z−1/2; (iii) x−1, y, z; (iv) x, −y+1/2, z+1/2; (v) −x, −y, −z; (vi) −x+1, −y, −z. |
Experimental details
Crystal data | |
Chemical formula | H3PO4·C3H5N2+·H2PO4− |
Mr | 264.07 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 296 |
a, b, c (Å) | 9.138 (4), 14.605 (6), 7.516 (3) |
β (°) | 91.447 (6) |
V (Å3) | 1002.8 (7) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.46 |
Crystal size (mm) | 0.36 × 0.28 × 0.24 |
Data collection | |
Diffractometer | Bruker APEX CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.802, 0.895 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6101, 2291, 1895 |
Rint | 0.025 |
(sin θ/λ)max (Å−1) | 0.650 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.038, 0.079, 1.00 |
No. of reflections | 2291 |
No. of parameters | 162 |
No. of restraints | 40 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.28, −0.36 |
Computer programs: SMART (Bruker, 1999), SAINT (Bruker, 1999), SAINT, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), PLATON (Spek, 2003), SHELXL97.
N1—C2 | 1.303 (5) | P1—O12 | 1.5405 (16) |
N1—C5 | 1.351 (6) | P1—O11 | 1.5530 (16) |
C2—N3 | 1.311 (4) | P2—O23 | 1.5010 (16) |
N3—C4 | 1.369 (6) | P2—O24 | 1.5112 (17) |
C4—C5 | 1.299 (7) | P2—O22 | 1.5464 (16) |
P1—O13 | 1.4965 (16) | P2—O21 | 1.5565 (17) |
P1—O14 | 1.5125 (16) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O14i | 0.86 | 1.97 | 2.827 (4) | 177 |
N3—H3···O21 | 0.86 | 2.16 | 2.986 (4) | 160 |
O11—H11···O13ii | 0.82 | 1.79 | 2.587 (2) | 162 |
O12—H12···O23iii | 0.82 | 1.79 | 2.554 (2) | 155 |
O13—H13···O11iv | 0.82 | 1.82 | 2.587 (2) | 155 |
O14—H14···O14v | 0.82 | 1.67 | 2.461 (3) | 162 |
O21—H21···O23iv | 0.82 | 1.80 | 2.602 (2) | 165 |
O22—H22···O13 | 0.82 | 1.76 | 2.561 (2) | 164 |
O24—H24···O24vi | 0.82 | 1.67 | 2.441 (4) | 156 |
Symmetry codes: (i) −x, −y, −z+1; (ii) x, −y+1/2, z−1/2; (iii) x−1, y, z; (iv) x, −y+1/2, z+1/2; (v) −x, −y, −z; (vi) −x+1, −y, −z. |
Recently, there has been much interest in vanadium phosphate-based compounds, due mostly to their potential application as battery materials, electrochromic displays and catalysts (Padhi et al., 1997; Song et al., 2005; Whittingham, 2004; Whittingham et al., 2005). Since the early 1980 s, a new class of ionic liquids, based on imidazole (Imd), has also attracted great interest due to its potential commercial and environmental advantages (Seddon, 1997). These ionic liquids are solvent-free, allowing them, potentially, to behave in a very different manner from conventional ionic electrolytic solutions. They are also capable of operating over a wide range of temperature, from ambient to well over 373 K. The possible use of an imidazolium salt, ImdX, mixed with the corresponding lithium salt, LiX, could be very attractive for advanced lithium batteries. Such a battery might contain a lithium-containing anode material, an imidazolium electrolyte and a cathode containing a layered-structure vanadium oxide or phosphate. However, a concern with such a system is the possible intercalation of the imidazolium cations between the layers of the oxide/phosphate structures. Such intercalation compounds have not previously been reported. While studying these possible reactions, we accidentally synthesized the title compound, (I), containing only imidazolium cations and phosphate anions. This paper describes the crystal structure of this compound.
Colourless crystals of (I) were found to crystallize in the monoclinic system. The structure is of an ionic type with hydrogen bonding (Figs. 1 and 2). It contains two phosphate groups and one imidazolium cation. Some of the H atoms are disordered between the two phosphate groups so they alternate between H2PO4− and H3PO4. This disorder provides H atoms for all the short O—O distances (~2.5 Å), making them hydrogen bonds (Table 2). The imidazolium cation is also disordered between two orientations in about a 3:1 ratio. The strong hydrogen bonding in this structure is in addition to the electrostatic interactions between the phosphate anions and the imidazolium cations. Both PO4 tetrahedra (Table 1) have two short P—O distances in the range 1.50–1.51 Å, while the other two lie between 1.54 and 1.56 Å.