organic compounds
4-Methoxybenzamidinium acetate
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+·CH3CO2−, was synthesized by a reaction between 4-methoxybenzamidine (4-amidinoanisole) and acetic acid. In the cation, the amidinium group forms a dihedral angle of 11.65 (17)° with the mean plane of the benzene ring. The ionic components are associated in the crystal via N—H+⋯O− hydrogen bonds, resulting in a one-dimensional structure consisting of dimers and catemers and orientated approximately along the c axis.
Related literature
For the biological and pharmacological relevance of benzamidine, see: Powers & Harper (1999). For structural analysis of proton-transfer adducts containing molecules of biological interest, see: Portalone, (2011a); Portalone & Irrera (2011). For the supramolecular association in proton-transfer adducts containing benzamidinium cations, see; Portalone (2010, 2011b, 2012); Irrera & Portalone (2012a,b); Irrera et al. (2012). For hydrogen-bond motifs, see Bernstein et al. (1995). For standard bond lengths, see: Allen et al. (1987).
Experimental
Crystal data
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Refinement
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Data collection: CrysAlis PRO (Agilent, 2011); cell CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).
Supporting information
10.1107/S1600536812044911/tk5166sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536812044911/tk5166Isup2.hkl
4-Methoxybenzamidine (0.1 mmol, Fluka at 96% purity) was dissolved without further purification in 8 ml of a 20% solution of acetic acid and 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 one week.
All H atoms were identified in difference Fourier maps, but for
all C-bound H atoms were placed in calculated positions, with C—H = 0.93 Å (phenyl) and 0.89 - 1.01 Å (methyl), and refined as riding on their carrier atoms. The Uiso values were kept equal to 1.2Ueq(C, phenyl). and to 1.5Ueq(C, methyl). Positional and displacement parameters of H atoms of the amidinium group were refined, giving N—H distances in the range 0.88 (2) - 0.94 (3) Å.Data collection: CrysAlis PRO (Agilent, 2011); cell
CrysAlis PRO (Agilent, 2011); data reduction: CrysAlis PRO (Agilent, 2011); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).C8H11N2O+·C2H3O2− | F(000) = 448 |
Mr = 210.23 | Dx = 1.282 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yn | Cell parameters from 3220 reflections |
a = 8.7591 (14) Å | θ = 2.8–28.9° |
b = 6.5478 (8) Å | µ = 0.10 mm−1 |
c = 19.456 (3) Å | T = 298 K |
β = 102.580 (14)° | Tablets, colourless |
V = 1089.0 (3) Å3 | 0.21 × 0.18 × 0.15 mm |
Z = 4 |
Oxford Diffraction Xcalibur S CCD diffractometer | 2365 independent reflections |
Radiation source: Enhance (Mo) X-ray Source | 1834 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.040 |
Detector resolution: 16.0696 pixels mm-1 | θmax = 27.0°, θmin = 3.3° |
ω and ϕ scans | h = −11→11 |
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2011) | k = −8→8 |
Tmin = 0.980, Tmax = 0.986 | l = −24→24 |
14433 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)] = 0.056 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.141 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.08 | w = 1/[σ2(Fo2) + (0.0561P)2 + 0.3698P] where P = (Fo2 + 2Fc2)/3 |
2365 reflections | (Δ/σ)max < 0.001 |
156 parameters | Δρmax = 0.21 e Å−3 |
0 restraints | Δρmin = −0.15 e Å−3 |
C8H11N2O+·C2H3O2− | V = 1089.0 (3) Å3 |
Mr = 210.23 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 8.7591 (14) Å | µ = 0.10 mm−1 |
b = 6.5478 (8) Å | T = 298 K |
c = 19.456 (3) Å | 0.21 × 0.18 × 0.15 mm |
β = 102.580 (14)° |
Oxford Diffraction Xcalibur S CCD diffractometer | 2365 independent reflections |
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2011) | 1834 reflections with I > 2σ(I) |
Tmin = 0.980, Tmax = 0.986 | Rint = 0.040 |
14433 measured reflections |
R[F2 > 2σ(F2)] = 0.056 | 0 restraints |
wR(F2) = 0.141 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.08 | Δρmax = 0.21 e Å−3 |
2365 reflections | Δρmin = −0.15 e Å−3 |
156 parameters |
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 | ||
O3 | 0.2977 (2) | 1.0070 (2) | 0.35136 (8) | 0.0624 (5) | |
N1 | −0.0153 (2) | 0.1780 (3) | 0.42774 (8) | 0.0453 (4) | |
H1A | −0.074 (3) | 0.064 (4) | 0.4296 (12) | 0.063 (7)* | |
H1B | 0.054 (3) | 0.217 (4) | 0.4677 (13) | 0.063 (7)* | |
N2 | −0.1170 (2) | 0.2005 (3) | 0.31128 (9) | 0.0468 (4) | |
H2A | −0.175 (3) | 0.081 (4) | 0.3149 (12) | 0.070 (7)* | |
H2B | −0.133 (3) | 0.261 (3) | 0.2696 (13) | 0.055 (6)* | |
C1 | 0.0643 (2) | 0.4636 (3) | 0.36478 (9) | 0.0343 (4) | |
C2 | 0.1370 (2) | 0.5636 (3) | 0.42564 (10) | 0.0449 (5) | |
H2 | 0.1318 | 0.5077 | 0.4690 | 0.054* | |
C3 | 0.2173 (2) | 0.7446 (3) | 0.42381 (10) | 0.0472 (5) | |
H3 | 0.2659 | 0.8088 | 0.4655 | 0.057* | |
C4 | 0.2248 (2) | 0.8294 (3) | 0.35969 (10) | 0.0429 (5) | |
C5 | 0.1539 (3) | 0.7298 (4) | 0.29855 (10) | 0.0584 (6) | |
H5 | 0.1594 | 0.7856 | 0.2552 | 0.070* | |
C6 | 0.0756 (3) | 0.5502 (3) | 0.30090 (10) | 0.0510 (5) | |
H6 | 0.0293 | 0.4849 | 0.2591 | 0.061* | |
C7 | −0.0247 (2) | 0.2737 (3) | 0.36775 (9) | 0.0356 (4) | |
C8 | 0.3954 (3) | 1.0997 (4) | 0.41088 (13) | 0.0624 (6) | |
H8A | 0.3323 (10) | 1.130 (2) | 0.4474 (7) | 0.094* | |
H8B | 0.4395 (17) | 1.231 (2) | 0.3962 (3) | 0.094* | |
H8C | 0.4838 (17) | 1.0040 (17) | 0.4315 (6) | 0.094* | |
O1 | −0.20216 (18) | −0.1693 (2) | 0.44118 (7) | 0.0548 (4) | |
O2 | −0.29092 (18) | −0.1444 (2) | 0.32662 (7) | 0.0550 (4) | |
C9 | −0.2818 (2) | −0.2339 (3) | 0.38404 (9) | 0.0390 (4) | |
C10 | −0.3743 (3) | −0.4258 (3) | 0.38417 (12) | 0.0606 (6) | |
H10A | −0.3120 (10) | −0.5337 (17) | 0.3841 (9) | 0.091* | |
H10B | −0.4519 (17) | −0.4292 (13) | 0.3458 (7) | 0.091* | |
H10C | −0.4143 (17) | −0.4291 (12) | 0.4226 (7) | 0.091* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O3 | 0.0827 (11) | 0.0586 (9) | 0.0449 (9) | −0.0302 (8) | 0.0113 (8) | 0.0040 (7) |
N1 | 0.0564 (11) | 0.0443 (10) | 0.0298 (8) | −0.0120 (8) | −0.0020 (7) | 0.0052 (7) |
N2 | 0.0613 (11) | 0.0439 (10) | 0.0293 (9) | −0.0095 (8) | −0.0034 (8) | 0.0040 (7) |
C1 | 0.0389 (10) | 0.0354 (9) | 0.0271 (9) | 0.0018 (7) | 0.0039 (7) | 0.0009 (7) |
C2 | 0.0616 (13) | 0.0460 (11) | 0.0263 (9) | −0.0063 (9) | 0.0076 (8) | 0.0021 (8) |
C3 | 0.0616 (13) | 0.0474 (11) | 0.0302 (10) | −0.0119 (9) | 0.0049 (9) | −0.0056 (8) |
C4 | 0.0485 (11) | 0.0423 (10) | 0.0379 (10) | −0.0043 (8) | 0.0092 (8) | 0.0012 (8) |
C5 | 0.0798 (16) | 0.0647 (14) | 0.0292 (10) | −0.0221 (12) | 0.0083 (10) | 0.0075 (9) |
C6 | 0.0686 (14) | 0.0545 (12) | 0.0270 (10) | −0.0158 (10) | 0.0037 (9) | −0.0019 (8) |
C7 | 0.0411 (10) | 0.0358 (9) | 0.0279 (9) | 0.0021 (7) | 0.0030 (7) | 0.0007 (7) |
C8 | 0.0673 (15) | 0.0587 (14) | 0.0587 (14) | −0.0234 (11) | 0.0086 (12) | −0.0064 (11) |
O1 | 0.0657 (10) | 0.0627 (9) | 0.0293 (7) | −0.0192 (7) | −0.0045 (6) | 0.0027 (6) |
O2 | 0.0742 (10) | 0.0551 (9) | 0.0281 (7) | −0.0154 (7) | −0.0053 (7) | 0.0019 (6) |
C9 | 0.0376 (10) | 0.0436 (10) | 0.0330 (10) | −0.0009 (8) | 0.0014 (8) | −0.0003 (8) |
C10 | 0.0608 (14) | 0.0558 (13) | 0.0603 (15) | −0.0123 (11) | 0.0023 (12) | 0.0026 (11) |
O3—C4 | 1.353 (2) | C3—H3 | 0.9300 |
O3—C8 | 1.418 (3) | C4—C5 | 1.380 (3) |
N1—C7 | 1.312 (2) | C5—C6 | 1.367 (3) |
N1—H1A | 0.91 (3) | C5—H5 | 0.9300 |
N1—H1B | 0.91 (2) | C6—H6 | 0.9300 |
N2—C7 | 1.306 (2) | C8—H8A | 1.0093 |
N2—H2A | 0.94 (3) | C8—H8B | 1.0093 |
N2—H2B | 0.88 (2) | C8—H8C | 1.0093 |
C1—C2 | 1.381 (2) | O1—C9 | 1.250 (2) |
C1—C6 | 1.389 (3) | O2—C9 | 1.249 (2) |
C1—C7 | 1.475 (2) | C9—C10 | 1.495 (3) |
C2—C3 | 1.383 (3) | C10—H10A | 0.8930 |
C2—H2 | 0.9300 | C10—H10B | 0.8930 |
C3—C4 | 1.380 (3) | C10—H10C | 0.8930 |
C4—O3—C8 | 119.11 (16) | C5—C6—C1 | 121.01 (18) |
C7—N1—H1A | 120.0 (14) | C5—C6—H6 | 119.5 |
C7—N1—H1B | 121.9 (15) | C1—C6—H6 | 119.5 |
H1A—N1—H1B | 118 (2) | N2—C7—N1 | 118.69 (18) |
C7—N2—H2A | 119.1 (14) | N2—C7—C1 | 120.84 (16) |
C7—N2—H2B | 123.6 (14) | N1—C7—C1 | 120.45 (16) |
H2A—N2—H2B | 117 (2) | O3—C8—H8A | 109.5 |
C2—C1—C6 | 117.64 (17) | O3—C8—H8B | 109.5 |
C2—C1—C7 | 120.99 (16) | H8A—C8—H8B | 109.5 |
C6—C1—C7 | 121.36 (16) | O3—C8—H8C | 109.5 |
C1—C2—C3 | 121.77 (17) | H8A—C8—H8C | 109.5 |
C1—C2—H2 | 119.1 | H8B—C8—H8C | 109.5 |
C3—C2—H2 | 119.1 | O2—C9—O1 | 123.45 (18) |
C4—C3—C2 | 119.52 (17) | O2—C9—C10 | 117.82 (16) |
C4—C3—H3 | 120.2 | O1—C9—C10 | 118.71 (17) |
C2—C3—H3 | 120.2 | C9—C10—H10A | 109.5 |
O3—C4—C5 | 116.00 (17) | C9—C10—H10B | 109.5 |
O3—C4—C3 | 124.78 (17) | H10A—C10—H10B | 109.5 |
C5—C4—C3 | 119.22 (18) | C9—C10—H10C | 109.5 |
C6—C5—C4 | 120.83 (18) | H10A—C10—H10C | 109.5 |
C6—C5—H5 | 119.6 | H10B—C10—H10C | 109.5 |
C4—C5—H5 | 119.6 | ||
C6—C1—C2—C3 | 0.6 (3) | C3—C4—C5—C6 | 0.6 (4) |
C7—C1—C2—C3 | −178.24 (18) | C4—C5—C6—C1 | 0.5 (4) |
C1—C2—C3—C4 | 0.4 (3) | C2—C1—C6—C5 | −1.1 (3) |
C8—O3—C4—C5 | −169.3 (2) | C7—C1—C6—C5 | 177.8 (2) |
C8—O3—C4—C3 | 10.9 (3) | C2—C1—C7—N2 | 167.00 (19) |
C2—C3—C4—O3 | 178.89 (19) | C6—C1—C7—N2 | −11.9 (3) |
C2—C3—C4—C5 | −1.0 (3) | C2—C1—C7—N1 | −11.3 (3) |
O3—C4—C5—C6 | −179.3 (2) | C6—C1—C7—N1 | 169.9 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O1 | 0.91 (3) | 1.94 (3) | 2.847 (2) | 175 (2) |
N1—H1B···O1i | 0.91 (2) | 1.98 (2) | 2.832 (2) | 155 (2) |
N2—H2A···O2 | 0.94 (3) | 1.83 (3) | 2.776 (2) | 176 (2) |
N2—H2B···O2ii | 0.88 (2) | 1.95 (2) | 2.817 (2) | 168 (2) |
Symmetry codes: (i) −x, −y, −z+1; (ii) −x−1/2, y+1/2, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C8H11N2O+·C2H3O2− |
Mr | 210.23 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 298 |
a, b, c (Å) | 8.7591 (14), 6.5478 (8), 19.456 (3) |
β (°) | 102.580 (14) |
V (Å3) | 1089.0 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.10 |
Crystal size (mm) | 0.21 × 0.18 × 0.15 |
Data collection | |
Diffractometer | Oxford Diffraction Xcalibur S CCD diffractometer |
Absorption correction | Multi-scan (CrysAlis PRO; Agilent, 2011) |
Tmin, Tmax | 0.980, 0.986 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 14433, 2365, 1834 |
Rint | 0.040 |
(sin θ/λ)max (Å−1) | 0.638 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.056, 0.141, 1.08 |
No. of reflections | 2365 |
No. of parameters | 156 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.21, −0.15 |
Computer programs: CrysAlis PRO (Agilent, 2011), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997), WinGX (Farrugia, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O1 | 0.91 (3) | 1.94 (3) | 2.847 (2) | 175 (2) |
N1—H1B···O1i | 0.91 (2) | 1.98 (2) | 2.832 (2) | 155 (2) |
N2—H2A···O2 | 0.94 (3) | 1.83 (3) | 2.776 (2) | 176 (2) |
N2—H2B···O2ii | 0.88 (2) | 1.95 (2) | 2.817 (2) | 168 (2) |
Symmetry codes: (i) −x, −y, −z+1; (ii) −x−1/2, y+1/2, −z+1/2. |
References
Agilent (2011). CrysAlis PRO. Agilent Technologies, Yarnton, England. Google Scholar
Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19. CrossRef Web of Science Google Scholar
Altomare, A., Burla, M. C., Camalli, M., Cascarano, G. L., Giacovazzo, C., Guagliardi, A., Moliterni, A. G. G., Polidori, G. & Spagna, R. (1999). J. Appl. Cryst. 32, 115–119. Web of Science CrossRef CAS IUCr Journals Google Scholar
Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555–1573. CrossRef CAS Web of Science Google Scholar
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565. CrossRef IUCr Journals Google Scholar
Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838. CrossRef CAS IUCr Journals Google Scholar
Irrera, S., Ortaggi, G. & Portalone, G. (2012). Acta Cryst. C68, o447–o451. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Irrera, S. & Portalone, G. (2012a). Acta Cryst. E68, o3083. CSD CrossRef IUCr Journals Google Scholar
Irrera, S. & Portalone, G. (2012b). Acta Cryst. E68, o3244. CSD CrossRef IUCr Journals Google Scholar
Portalone, G. (2010). Acta Cryst. C66, o295–o301. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Portalone, G. (2011a). Chem. Centr. J. 5, 51. Web of Science CSD CrossRef Google Scholar
Portalone, G. (2011b). Acta Cryst. E67, o3394–o3395. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Portalone, G. (2012). Acta Cryst. E68, o268–o269. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Portalone, G. & Irrera, S. (2011). J. Mol. Struct. 991, 92–96. Web of Science CSD CrossRef CAS Google Scholar
Powers, J. C. & Harper, J. W. (1999). Proteinase inhibitors, edited by A. J. Barrett & G. Salvesen, pp. 55–152. Elsevier: Amsterdam. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
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.
The present work is part of a general structural analysis of proton-transfer adducts containing molecules of biological interest (Portalone, 2011a; Portalone & Irrera, 2011). In this context, benzamidine derivatives, which have shown strong biological and pharmacological activity (Powers & Harper, 1999), are being used in our group as bricks for supramolecular construction (Portalone, 2010, 2011b, 2012). Indeed, the bidentate hydrogen-bonding interaction between the amidinium and the carboxylate functional groups can be a powerful organizing force in solution and in the solid-state.
We report here the single-crystal structure of the title molecular salt, 4-methoxybenzamidinium acetate, (I), which was obtained by a reaction between 4-methoxybenzamidine (4-amidinoanisole) and acetic acid.
The asymmetric unit of (I) comprises one non-planar 4-methoxybenzamidinium cation and one acetate anion (Fig. 1).
In the cation the amidinium group forms dihedral angle of 11.65 (17)° with the mean plane of the phenyl ring, which agrees with the values observed in protonated benzamidinium ions (14.4 (1) - 32.7 (1)°, Portalone, 2010, 2012; Irrera et al., 2012). 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. This conformation is rather common in benzamidinium-containing small-molecule crystal structures, with the only exception of benzamidinium diliturate, where the benzamidinium cation is planar (Portalone, 2010). The pattern of bond lengths and bond angles of the 4-methoxybenzamidinium cation agrees with that reported in previous structural investigations (Irrera et al., 2012; Portalone, 2010, 2012; Irrera & Portalone, 2012a, 2012b). In particular the amidinium group, true to one's expectations, features C—N bonds within experimental error [1.312 (2) and 1.306 (2) Å], evidencing the delocalization of the π electrons and double-bond character.
In the acetate moiety the C—O bond lengths indicate delocalization of the negative charge on both O atoms, since the C—O bond lengths [1.250 (2) and 1.249 (2) Å] are intermediate between single Csp2—O and double Csp2═O, and correlate well with values for carboxylate anions [1.247 - 1.262 Å, Allen et al., 1987].
Analysis of the crystal packing of (I), (Fig. 2), shows that each amidinium unit is bound to three acetate anions by four distinct N—H+···O- strong intermolecular hydrogen bonds (N+···O- = 2.776 (2) - 2.847 (2) Å, Table 1) into a one-dimensional structure. The ion pairs of the asymmetric unit are joined by two N+—H···O- (±) hydrogen bonds to form ionic dimers with graph-set motif R22(8) (Bernstein et al., 1995). These subunits are then joined as catemers into linear chains approximately along the crystallographic c axis through the remaining N+—H···O- hydrogen bonds to adjacent anti-parallel dimers.