organic compounds
4-Methoxybenzamidinium 2,6-dimethoxybenzoate
aChemistry Department, "Sapienza" University of Rome, P.le A. Moro, 5, I-00185 Rome, Italy
*Correspondence e-mail: g.portalone@caspur.it
The title compound, C8H11N2O+·C9H9O4−, was synthesized by the reaction of 4-methoxybenzamidine (4-amidinoanisole) and 2,6-dimethoxybenzoic acid. The structure consists of non-planar pairs of hydrogen-bonded 4-methoxybenzamidinium cations and 2,6-dimethoxybenzoate anions. In the cation, the amidinium group is tilted by 27.94 (10)° with respect to the benzene ring. In the anion, the sterically bulky ortho-methoxy substituents force the carboxyate group to be twisted away from the plane of the benzene ring by 73.24 (6)°. The ions are further associated in the crystal into chains along the b-axis direction by intermolecular N—H⋯O hydrogen bonds.
Related literature
For the biological and pharmacological relevance of benzamidine, see: Marquart et al. (1983); Sprang et al. (1987); Bode et al. (1990); Powers & Harper (1999); Grzesiak et al. (2000). For the structure of benzamidine, see: Barker et al. (1996). For supramolecular association in proton-transfer adducts containing benzamidinium cations, see; Papoutsakis et al. (1999); Portalone (2008, 2010). For the structure of benzdiamidine, see: Jokić et al. (2001). For the orthorhombic and tetragonal polymorphs of 2,6-dimethoxybenzoic acid, see: Swaminathan et al. (1976); Bryan & White (1982); Portalone (2009, 2011). For the analysis of benzene ring deformations induced by substitution, see: Schultz et al. (1993); Portalone et al. (1998); For computation of ring patterns formed by hydrogen bonds in crystal structures, see: Etter et al. (1990); Bernstein et al. (1995); Motherwell et al. (1999).
Experimental
Crystal data
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Refinement
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Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED; program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: WinGX (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).
Supporting information
10.1107/S160053681105519X/rz2691sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S160053681105519X/rz2691Isup2.hkl
Supporting information file. DOI: 10.1107/S160053681105519X/rz2691Isup3.cml
The title compound was formed during cocrystallization in a 1:1 molar ratio of 2,6-dimethoxybenzoic acid (1 mmol, Aldrich at 98% purity) and 4-methoxybenzamidine (1 mmol, Fluka at 96% purity). The two components were dissolved in water (10 ml) and gently heated under reflux for 3 h. After cooling the solution to an ambient temperature, colourless crystals suitable for single-crystal X-ray diffraction were grown by slow evaporation of the solvent after two weeks.
The amine H atoms were located in a difference Fourier map and refined freely. All other H atoms could be identified in difference Fourier maps, but were placed in calculated positions, with C—H = 0.97 Å (phenyl) and 0.99 Å (methyl), and refined as riding on their carrier atoms. The Uiso values were kept equal to 1.2Ueq(C) or 1.5Ueq(C) for methyl H atoms.
Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell
CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: WinGX (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).C8H11N2O+·C9H9O4− | F(000) = 704 |
Mr = 332.35 | Dx = 1.324 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71069 Å |
Hall symbol: -P 2ybc | Cell parameters from 41031 reflections |
a = 12.6594 (3) Å | θ = 2.9–34.8° |
b = 9.6754 (2) Å | µ = 0.10 mm−1 |
c = 13.7923 (4) Å | T = 298 K |
β = 99.241 (2)° | Tablets, colourless |
V = 1667.42 (7) Å3 | 0.30 × 0.30 × 0.25 mm |
Z = 4 |
Oxford Diffraction Xcalibur S CCD diffractometer | 4217 independent reflections |
Radiation source: Enhance (Mo) X-ray source | 3914 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.026 |
Detector resolution: 16.0696 pixels mm-1 | θmax = 28.5°, θmin = 2.9° |
ω and ϕ scans | h = −16→16 |
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006) | k = −12→12 |
Tmin = 0.971, Tmax = 0.976 | l = −18→18 |
76316 measured reflections |
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)] = 0.060 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.131 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.17 | w = 1/[σ2(Fo2) + (0.0405P)2 + 0.878P] where P = (Fo2 + 2Fc2)/3 |
4217 reflections | (Δ/σ)max < 0.001 |
239 parameters | Δρmax = 0.32 e Å−3 |
0 restraints | Δρmin = −0.18 e Å−3 |
C8H11N2O+·C9H9O4− | V = 1667.42 (7) Å3 |
Mr = 332.35 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 12.6594 (3) Å | µ = 0.10 mm−1 |
b = 9.6754 (2) Å | T = 298 K |
c = 13.7923 (4) Å | 0.30 × 0.30 × 0.25 mm |
β = 99.241 (2)° |
Oxford Diffraction Xcalibur S CCD diffractometer | 4217 independent reflections |
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006) | 3914 reflections with I > 2σ(I) |
Tmin = 0.971, Tmax = 0.976 | Rint = 0.026 |
76316 measured reflections |
R[F2 > 2σ(F2)] = 0.060 | 0 restraints |
wR(F2) = 0.131 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.17 | Δρmax = 0.32 e Å−3 |
4217 reflections | Δρmin = −0.18 e Å−3 |
239 parameters |
Experimental. CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.32.29 (release 10-06-2008 CrysAlis171 .NET) (compiled Jun 10 2008,16:49:55) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. |
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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 | ||
O5 | 0.10799 (10) | −0.11594 (17) | −0.24016 (10) | 0.0540 (4) | |
N1 | 0.44446 (13) | −0.09706 (15) | 0.15597 (11) | 0.0413 (4) | |
H1A | 0.4973 (17) | −0.110 (2) | 0.2099 (16) | 0.049 (6)* | |
H1B | 0.4294 (17) | −0.011 (2) | 0.1385 (15) | 0.045 (5)* | |
N2 | 0.39964 (14) | −0.32294 (16) | 0.15666 (14) | 0.0467 (4) | |
H2A | 0.442 (2) | −0.329 (3) | 0.2161 (19) | 0.063 (7)* | |
H2B | 0.3761 (19) | −0.396 (3) | 0.1250 (18) | 0.059 (7)* | |
C1 | 0.31657 (12) | −0.17948 (16) | 0.02049 (11) | 0.0303 (3) | |
C2 | 0.33754 (13) | −0.07531 (19) | −0.04288 (12) | 0.0376 (4) | |
H2 | 0.4006 | −0.0181 | −0.0250 | 0.045* | |
C3 | 0.27065 (13) | −0.0509 (2) | −0.13109 (13) | 0.0408 (4) | |
H3 | 0.2871 | 0.0216 | −0.1749 | 0.049* | |
C4 | 0.17991 (13) | −0.13163 (19) | −0.15559 (12) | 0.0375 (4) | |
C5 | 0.15748 (13) | −0.2361 (2) | −0.09328 (14) | 0.0426 (4) | |
H5 | 0.0939 | −0.2924 | −0.1109 | 0.051* | |
C6 | 0.22544 (13) | −0.26050 (18) | −0.00599 (13) | 0.0388 (4) | |
H6 | 0.2096 | −0.3344 | 0.0370 | 0.047* | |
C7 | 0.38977 (12) | −0.20070 (15) | 0.11435 (12) | 0.0316 (3) | |
C17 | 0.12111 (18) | 0.0003 (3) | −0.30073 (15) | 0.0591 (6) | |
H17A | 0.1146 (14) | 0.0864 (14) | −0.2636 (7) | 0.089* | |
H17B | 0.0653 (12) | −0.0014 (10) | −0.3597 (11) | 0.089* | |
H17C | 0.1925 (12) | −0.0034 (10) | −0.3209 (11) | 0.089* | |
O1 | 0.61718 (10) | −0.11290 (12) | 0.30539 (9) | 0.0400 (3) | |
O2 | 0.55414 (10) | −0.31629 (12) | 0.34359 (10) | 0.0421 (3) | |
O3 | 0.63894 (11) | −0.06691 (15) | 0.52149 (10) | 0.0517 (4) | |
O4 | 0.78817 (10) | −0.40567 (14) | 0.34411 (9) | 0.0447 (3) | |
C8 | 0.71797 (11) | −0.23514 (15) | 0.43547 (11) | 0.0276 (3) | |
C9 | 0.72422 (14) | −0.15283 (17) | 0.51889 (12) | 0.0366 (4) | |
C10 | 0.81319 (17) | −0.1596 (2) | 0.59275 (14) | 0.0523 (5) | |
H10 | 0.8165 | −0.1042 | 0.6518 | 0.063* | |
C11 | 0.89636 (15) | −0.2462 (2) | 0.58046 (15) | 0.0524 (5) | |
H11 | 0.9593 | −0.2491 | 0.6308 | 0.063* | |
C12 | 0.89261 (13) | −0.3286 (2) | 0.49875 (13) | 0.0425 (4) | |
H12 | 0.9522 | −0.3885 | 0.4914 | 0.051* | |
C13 | 0.80189 (12) | −0.32480 (16) | 0.42671 (11) | 0.0315 (3) | |
C14 | 0.62180 (11) | −0.22199 (15) | 0.35457 (10) | 0.0270 (3) | |
C15 | 0.62678 (17) | −0.0059 (2) | 0.61327 (15) | 0.0523 (5) | |
H15A | 0.6294 (13) | −0.0783 (10) | 0.6634 (8) | 0.078* | |
H15B | 0.5577 (11) | 0.0421 (16) | 0.6066 (3) | 0.078* | |
H15C | 0.6849 (11) | 0.0606 (15) | 0.6329 (7) | 0.078* | |
C16 | 0.86484 (16) | −0.5108 (2) | 0.33788 (14) | 0.0477 (5) | |
H16A | 0.9338 (10) | −0.4683 (6) | 0.3302 (11) | 0.071* | |
H16B | 0.8399 (7) | −0.5704 (12) | 0.2808 (10) | 0.071* | |
H16C | 0.8742 (9) | −0.5669 (13) | 0.3984 (9) | 0.071* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O5 | 0.0399 (7) | 0.0729 (10) | 0.0426 (7) | −0.0057 (7) | −0.0136 (6) | −0.0001 (7) |
N1 | 0.0484 (8) | 0.0244 (7) | 0.0428 (8) | 0.0029 (6) | −0.0181 (7) | 0.0010 (6) |
N2 | 0.0499 (9) | 0.0259 (7) | 0.0573 (10) | 0.0001 (6) | −0.0121 (8) | 0.0043 (7) |
C1 | 0.0278 (7) | 0.0275 (7) | 0.0339 (7) | 0.0028 (6) | −0.0002 (6) | −0.0054 (6) |
C2 | 0.0279 (7) | 0.0432 (9) | 0.0391 (9) | −0.0068 (7) | −0.0025 (6) | 0.0002 (7) |
C3 | 0.0344 (8) | 0.0496 (10) | 0.0363 (8) | −0.0056 (7) | −0.0002 (6) | 0.0046 (7) |
C4 | 0.0280 (7) | 0.0481 (10) | 0.0340 (8) | 0.0026 (7) | −0.0022 (6) | −0.0077 (7) |
C5 | 0.0310 (8) | 0.0456 (10) | 0.0478 (10) | −0.0105 (7) | −0.0042 (7) | −0.0070 (8) |
C6 | 0.0371 (8) | 0.0335 (8) | 0.0440 (9) | −0.0063 (7) | 0.0005 (7) | −0.0015 (7) |
C7 | 0.0307 (7) | 0.0247 (7) | 0.0372 (8) | 0.0049 (6) | −0.0013 (6) | −0.0019 (6) |
C17 | 0.0533 (12) | 0.0791 (16) | 0.0397 (10) | 0.0039 (11) | −0.0081 (8) | 0.0063 (10) |
O1 | 0.0410 (6) | 0.0318 (6) | 0.0416 (6) | −0.0013 (5) | −0.0104 (5) | 0.0114 (5) |
O2 | 0.0363 (6) | 0.0267 (6) | 0.0568 (8) | −0.0032 (5) | −0.0126 (5) | 0.0046 (5) |
O3 | 0.0525 (8) | 0.0551 (8) | 0.0425 (7) | 0.0201 (6) | −0.0072 (6) | −0.0171 (6) |
O4 | 0.0446 (7) | 0.0508 (7) | 0.0354 (6) | 0.0217 (6) | −0.0034 (5) | −0.0049 (5) |
C8 | 0.0273 (7) | 0.0251 (7) | 0.0279 (7) | −0.0004 (5) | −0.0027 (5) | 0.0048 (5) |
C9 | 0.0378 (8) | 0.0331 (8) | 0.0356 (8) | 0.0037 (6) | −0.0043 (6) | −0.0027 (6) |
C10 | 0.0547 (11) | 0.0540 (12) | 0.0405 (10) | 0.0065 (9) | −0.0154 (8) | −0.0128 (9) |
C11 | 0.0418 (10) | 0.0579 (12) | 0.0486 (11) | 0.0046 (9) | −0.0204 (8) | −0.0008 (9) |
C12 | 0.0302 (8) | 0.0475 (10) | 0.0459 (10) | 0.0094 (7) | −0.0052 (7) | 0.0060 (8) |
C13 | 0.0310 (7) | 0.0326 (8) | 0.0295 (7) | 0.0035 (6) | −0.0001 (6) | 0.0054 (6) |
C14 | 0.0272 (7) | 0.0237 (7) | 0.0281 (7) | 0.0064 (5) | −0.0018 (5) | −0.0015 (5) |
C15 | 0.0532 (11) | 0.0604 (12) | 0.0452 (10) | 0.0034 (9) | 0.0133 (9) | −0.0112 (9) |
C16 | 0.0494 (10) | 0.0501 (11) | 0.0445 (10) | 0.0213 (9) | 0.0103 (8) | 0.0032 (8) |
O5—C4 | 1.3680 (19) | O1—C14 | 1.2509 (18) |
O5—C17 | 1.427 (3) | O2—C14 | 1.2440 (18) |
N1—C7 | 1.299 (2) | O3—C9 | 1.368 (2) |
N1—H1A | 0.93 (2) | O3—C15 | 1.427 (2) |
N1—H1B | 0.88 (2) | O4—C13 | 1.370 (2) |
N2—C7 | 1.316 (2) | O4—C16 | 1.418 (2) |
N2—H2A | 0.91 (3) | C8—C9 | 1.391 (2) |
N2—H2B | 0.86 (3) | C8—C13 | 1.392 (2) |
C1—C2 | 1.387 (2) | C8—C14 | 1.5189 (18) |
C1—C6 | 1.394 (2) | C9—C10 | 1.394 (2) |
C1—C7 | 1.480 (2) | C10—C11 | 1.377 (3) |
C2—C3 | 1.386 (2) | C10—H10 | 0.9700 |
C2—H2 | 0.9700 | C11—C12 | 1.375 (3) |
C3—C4 | 1.386 (2) | C11—H11 | 0.9700 |
C3—H3 | 0.9700 | C12—C13 | 1.393 (2) |
C4—C5 | 1.385 (3) | C12—H12 | 0.9700 |
C5—C6 | 1.383 (2) | C15—H15A | 0.9817 |
C5—H5 | 0.9700 | C15—H15B | 0.9817 |
C6—H6 | 0.9700 | C15—H15C | 0.9817 |
C17—H17A | 0.9877 | C16—H16A | 0.9865 |
C17—H17B | 0.9877 | C16—H16B | 0.9865 |
C17—H17C | 0.9877 | C16—H16C | 0.9865 |
C4—O5—C17 | 117.56 (15) | C13—O4—C16 | 117.61 (13) |
C7—N1—H1A | 120.8 (13) | C9—C8—C13 | 119.07 (13) |
C7—N1—H1B | 122.1 (14) | C9—C8—C14 | 119.47 (13) |
H1A—N1—H1B | 116.8 (19) | C13—C8—C14 | 121.43 (13) |
C7—N2—H2A | 117.3 (16) | O3—C9—C8 | 115.43 (13) |
C7—N2—H2B | 120.8 (16) | O3—C9—C10 | 123.91 (16) |
H2A—N2—H2B | 121 (2) | C8—C9—C10 | 120.65 (16) |
C2—C1—C6 | 118.52 (14) | C11—C10—C9 | 118.85 (17) |
C2—C1—C7 | 119.69 (14) | C11—C10—H10 | 120.6 |
C6—C1—C7 | 121.78 (15) | C9—C10—H10 | 120.6 |
C3—C2—C1 | 121.67 (15) | C12—C11—C10 | 121.83 (16) |
C3—C2—H2 | 119.2 | C12—C11—H11 | 119.1 |
C1—C2—H2 | 119.2 | C10—C11—H11 | 119.1 |
C4—C3—C2 | 118.91 (16) | C11—C12—C13 | 119.02 (16) |
C4—C3—H3 | 120.5 | C11—C12—H12 | 120.5 |
C2—C3—H3 | 120.5 | C13—C12—H12 | 120.5 |
O5—C4—C5 | 115.80 (15) | O4—C13—C8 | 115.57 (13) |
O5—C4—C3 | 123.89 (17) | O4—C13—C12 | 123.92 (15) |
C5—C4—C3 | 120.31 (15) | C8—C13—C12 | 120.52 (15) |
C6—C5—C4 | 120.24 (15) | O2—C14—O1 | 125.56 (13) |
C6—C5—H5 | 119.9 | O2—C14—C8 | 118.88 (13) |
C4—C5—H5 | 119.9 | O1—C14—C8 | 115.54 (13) |
C5—C6—C1 | 120.34 (16) | O3—C15—H15A | 109.5 |
C5—C6—H6 | 119.8 | O3—C15—H15B | 109.5 |
C1—C6—H6 | 119.8 | H15A—C15—H15B | 109.5 |
N1—C7—N2 | 119.47 (15) | O3—C15—H15C | 109.5 |
N1—C7—C1 | 119.60 (14) | H15A—C15—H15C | 109.5 |
N2—C7—C1 | 120.93 (15) | H15B—C15—H15C | 109.5 |
O5—C17—H17A | 109.5 | O4—C16—H16A | 109.5 |
O5—C17—H17B | 109.5 | O4—C16—H16B | 109.5 |
H17A—C17—H17B | 109.5 | H16A—C16—H16B | 109.5 |
O5—C17—H17C | 109.5 | O4—C16—H16C | 109.5 |
H17A—C17—H17C | 109.5 | H16A—C16—H16C | 109.5 |
H17B—C17—H17C | 109.5 | H16B—C16—H16C | 109.5 |
C9—O3—C15 | 118.21 (14) | ||
C6—C1—C2—C3 | −0.2 (3) | C14—C8—C9—O3 | 1.5 (2) |
C7—C1—C2—C3 | −179.38 (16) | C13—C8—C9—C10 | 0.1 (3) |
C1—C2—C3—C4 | 0.9 (3) | C14—C8—C9—C10 | −177.89 (17) |
C17—O5—C4—C5 | 172.81 (18) | O3—C9—C10—C11 | −177.5 (2) |
C17—O5—C4—C3 | −7.5 (3) | C8—C9—C10—C11 | 1.9 (3) |
C2—C3—C4—O5 | 179.46 (17) | C9—C10—C11—C12 | −1.8 (3) |
C2—C3—C4—C5 | −0.8 (3) | C10—C11—C12—C13 | −0.3 (3) |
O5—C4—C5—C6 | 179.86 (17) | C16—O4—C13—C8 | −172.11 (15) |
C3—C4—C5—C6 | 0.1 (3) | C16—O4—C13—C12 | 8.1 (3) |
C4—C5—C6—C1 | 0.6 (3) | C9—C8—C13—O4 | 177.88 (15) |
C2—C1—C6—C5 | −0.5 (3) | C14—C8—C13—O4 | −4.2 (2) |
C7—C1—C6—C5 | 178.64 (16) | C9—C8—C13—C12 | −2.3 (2) |
C2—C1—C7—N1 | 27.6 (2) | C14—C8—C13—C12 | 175.68 (15) |
C6—C1—C7—N1 | −151.54 (17) | C11—C12—C13—O4 | −177.78 (17) |
C2—C1—C7—N2 | −152.93 (18) | C11—C12—C13—C8 | 2.4 (3) |
C6—C1—C7—N2 | 27.9 (2) | C9—C8—C14—O2 | −107.53 (17) |
C15—O3—C9—C8 | 164.66 (17) | C13—C8—C14—O2 | 74.5 (2) |
C15—O3—C9—C10 | −15.9 (3) | C9—C8—C14—O1 | 71.0 (2) |
C13—C8—C9—O3 | 179.53 (15) | C13—C8—C14—O1 | −106.91 (17) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O1 | 0.93 (2) | 1.84 (2) | 2.7576 (18) | 169 (2) |
N1—H1B···O2i | 0.88 (2) | 1.91 (2) | 2.7166 (18) | 152 (2) |
N2—H2B···O1ii | 0.86 (3) | 2.31 (2) | 2.868 (2) | 123 (2) |
N2—H2A···O2 | 0.91 (3) | 2.08 (3) | 2.976 (2) | 170 (2) |
Symmetry codes: (i) −x+1, y+1/2, −z+1/2; (ii) −x+1, y−1/2, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C8H11N2O+·C9H9O4− |
Mr | 332.35 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 298 |
a, b, c (Å) | 12.6594 (3), 9.6754 (2), 13.7923 (4) |
β (°) | 99.241 (2) |
V (Å3) | 1667.42 (7) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.10 |
Crystal size (mm) | 0.30 × 0.30 × 0.25 |
Data collection | |
Diffractometer | Oxford Diffraction Xcalibur S CCD diffractometer |
Absorption correction | Multi-scan (CrysAlis RED; Oxford Diffraction, 2006) |
Tmin, Tmax | 0.971, 0.976 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 76316, 4217, 3914 |
Rint | 0.026 |
(sin θ/λ)max (Å−1) | 0.671 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.060, 0.131, 1.17 |
No. of reflections | 4217 |
No. of parameters | 239 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.32, −0.18 |
Computer programs: CrysAlis CCD (Oxford Diffraction, 2006), CrysAlis RED (Oxford Diffraction, 2006), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 2008), WinGX (Farrugia, 1997), WinGX (Farrugia, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O1 | 0.93 (2) | 1.84 (2) | 2.7576 (18) | 169 (2) |
N1—H1B···O2i | 0.88 (2) | 1.91 (2) | 2.7166 (18) | 152 (2) |
N2—H2B···O1ii | 0.86 (3) | 2.31 (2) | 2.868 (2) | 123 (2) |
N2—H2A···O2 | 0.91 (3) | 2.08 (3) | 2.976 (2) | 170 (2) |
Symmetry codes: (i) −x+1, y+1/2, −z+1/2; (ii) −x+1, y−1/2, −z+1/2. |
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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
This Laboratory is currently engaged in the systematic structural analysis of molecular salts of benzamidine (Portalone, 2008, 2010). Benzamidine is a strong Lewis base and its cation can be easily anchored onto numerous inorganic and organic anions and polyanions, largely because of the presence of four potential donor sites for hydrogen-bonding. Consequently, benzamidinium ions appear to be very promising building blocks in supramolecular chemistry as multiple hydrogen bonding donor. Benzamidine has biological and pharmacological relevance (Powers & Harper, 1999; Grzesiak et al., 2000). Its cation has also been included in a number of protein structures (Marquart et al., 1983; Sprang et al., 1987; Bode et al., 1990).
The asymmetric unit of the title compound comprises a non-planar R22(8) hydrogen-bonded pair formed by one 4-methoxybenzamidinium cation and one 2,6-dimethoxybenzoate anion (Fig. 1). In the anion, the o-methoxy substituents force the carboxy group to be twisted away from the plane of the phenyl ring by 73.24 (6)°. The C—O distances of the carboxylate group range from 1.2440 (18) to 1.2509 (18) Å, indicating the delocalization of the negative charge. The pattern of bond lengths and bond angles of the phenyl ring is consistent with that reported in the structure determination of the two polymorphs of 2,6-dimethoxybenzoic acid (Swaminathan et al., 1976; Bryan & White, 1982; Portalone, 2009, 2011), and a comparison of the present results with those obtained for similar benzene derivatives in the gas phase (Schultz et al., 1993; Portalone et al., 1998) shows no appreciable effects of the crystal environment on the ring deformation induced by substituents. In the cation, the amidinium group forms a dihedral angle of 27.94 (10)° with the phenyl ring, which is close to the values observed in neutral benzamidine (22.8°, Barker et al., 1996) as well as in protonated benzamidinium (20.7°, Papoutsakis et al., 1999; 28.5 and 31.9°, Portalone, 2008, 2010) and benzdiamidine (24.5°, Jokić et al., 2001). The lack of planarity in all these systems is obviously caused by steric hindrances between the H atoms of the aromatic ring and the amidine moiety. The pattern of bond lengths and bond angles of the benzamidinium cation agrees with that reported in previous structural investigations (Papoutsakis et al., 1999; Portalone, 2008, 2010). In particular the amidinium group, true to one's expectations, features similar C-N bonds [1.299 (2) and 1.316 (2) Å], evidencing the delocalization of the π electrons and double-bond character.
Analysis of the crystal packing (Fig. 2) shows that the pairs are associated in the crystal by extensive hydrogen bonding. Those pairs of cations and anions are joined by intermolecular R44(8) N—H···O interactions (Etter et al., 1990; Bernstein et al., 1995; Motherwell et al., 1999) (Table 1) leading to a chain structure running along the b direction.