organic compounds
2-Amino-5-methylpyridinium 4-chlorobenzoate
aSchool of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia, and bDepartment of Physics, Faculty of Science, University of Mazandaran, Babolsar, Iran
*Correspondence e-mail: arazaki@usm.my
The 4-chlorobenzoate anion of the title salt, C6H9N2+·C7H4ClO2−, is nearly planar with a dihedral angle of 5.14 (16)° between the benzene ring and the carboxylate group. In the crystal, the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxylate O atoms of the anion via a pair of N—H⋯O hydrogen bonds with an R22(8) ring motif. The ion pairs are further connected via N—H⋯O and weak C—H⋯O hydrogen bonds, forming a two-dimensional network parallel to the bc plane. The also features a π–π stacking interaction between the pyridinium and benzene rings with a centroid–centroid distance of 3.7948 (9) Å.
Related literature
For background to the chemistry of substituted pyridines, see: Pozharski et al. (1997); Katritzky et al. (1996). For 4-chlorobenzoic acid, see: Dionysiou et al. (2000). For details of hydrogen-bonded supramolecular compounds, see: Aakeroy et al. (2002). For related structures, see: Nahringbauer & Kvick (1977); Thanigaimani et al. (2012a,b,c). For hydrogen-bond motifs, see: Bernstein et al. (1995). For bond-length data, see: Allen et al. (1987).
Experimental
Crystal data
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Refinement
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Data collection: APEX2 (Bruker, 2009); cell SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009).
Supporting information
https://doi.org/10.1107/S1600536812051021/is5231sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536812051021/is5231Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S1600536812051021/is5231Isup3.cml
Hot methanol solutions (20 ml) of 2-amino-5-methylpyridine (54 mg, Aldrich) and 4-chlorobenzoic acid (39 mg, Aldrich) were mixed and warmed over a heating magnetic stirrer hotplate for a few minutes. The resulting solution was allowed to cool slowly at room temperature and crystals of the title compound (I) appeared after a few days.
N-bound H Atoms were located in a difference Fourier maps and refined freely [refined N—H distances 0.98 (2), 0.92 (2) and 0.85 (2) Å]. The remaining H atoms were positioned geometrically (C—H = 0.93–0.96 Å) and were refined using a riding model, with Uiso(H) = 1.2Ueq(C) or 1.5Ueq(methyl C). A rotating group model was used for the methyl group. Three outliers were omitted (1 4 0, 1 1 0 and 3 1 2) in the final refinement.
In recent years, hydrogen bonds have attracted the interest of chemists and have been widely used to design and synthesize one, two and three-dimensional supramolecular compounds (Aakeroy et al., 2002). Pyridine and its derivatives play an important role in heterocyclic chemistry (Pozharski et al., 1997; Katritzky et al., 1996). They are often involved in hydrogen-bond interactions. 4-Chlorobenzoic acid (4-CBA) has been reported as intermediate product during biological or chemical degradation of pesticides and herbicides (Dionysiou et al., 2000). We have recently reported related crystal structures of 2-amino-5-methylpyridinium 3-chlorobenzoate (Thanigaimani et al., 2012a), 2-amino-5-methylpyridinium 2-aminobenzoate (Thanigaimani et al., 2012b) and 2-amino-5-methylpyridinium trifluoroacetate (Thanigaimani et al., 2012c). In order to study some interesting hydrogen bonding interactions of this compound, the synthesis and structure of the title salt is presented here.
The
(Fig. 1) contains one 2-amino-5-methylpyridinium cation and one 4-chlorobenzoate anion. The proton transfers from the carboxyl group oxygen atom (O1) to atom N1 of the 2-amino-5-methylpyrimidine resulted in the widening of C1—N1—C5 angle of the pyridinium ring to 122.06 (11)°, compared to the corresponding angle of 117.4 (3)° in neutral 2-amino-5-methylpyridine (Nahringbauer & Kvick, 1977). The 2-amino-5-methylpyridinium cation is essentially planar, with a maximum deviation of 0.005 (1) Å for atom C1. The carboxylate group of the 4-chlorobenzoate anion is slightly twisted from the attached ring with the dihedral angle between C7–C12 ring and O1/O2/C13 plane being 5.14 (16)°. The bond lengths (Allen et al., 1987) and angles are normal.In the crystal packing (Fig. 2), the protonated N1 atom and a nitrogen atom of the 2-amino group (N2) are hydrogen-bonded to the carboxylate oxygen atoms (O1 and O2) via a pair of intermolecular N1—H1N1···O1i and N2—H2N2···O2i hydrogen bonds (symmetry code in Table 1), forming a ring motif of R22(8) (Bernstein et al., 1995). Furthermore, these motifs are connected via N2—H1N2···O1 and C2—H2A···O2ii hydrogen bonds to form a two-dimensional network parallel to the bc plane. The π–π interactions between the pyridine (C1–C5/N1) and benzene (C7–C12) rings, with centroid to centroid distance of 3.7948 (9) Å (symmetry codes: 1 - x, -1/2 + y, 1/2 - z and 1 - x, 1/2 + y, 1/2 - z)
is further stabilized byFor background to the chemistry of substituted pyridines, see: Pozharski et al. (1997); Katritzky et al. (1996). For 4-chlorobenzoic acid, see: Dionysiou et al. (2000). For details of hydrogen-bonded supramolecular compounds, see: Aakeroy et al. (2002). For related structures, see: Nahringbauer & Kvick (1977); Thanigaimani et al. (2012a,b,c). For hydrogen-bond motifs, see: Bernstein et al. (1995). For bond-length data, see: Allen et al. (1987).
Data collection: APEX2 (Bruker, 2009); cell
SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).C6H9N2+·C7H4ClO2− | F(000) = 552 |
Mr = 264.70 | Dx = 1.389 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 3497 reflections |
a = 9.8510 (6) Å | θ = 2.6–26.9° |
b = 10.7707 (8) Å | µ = 0.30 mm−1 |
c = 12.2123 (7) Å | T = 297 K |
β = 102.335 (2)° | Plate, colourless |
V = 1265.84 (14) Å3 | 0.46 × 0.25 × 0.13 mm |
Z = 4 |
Bruker SMART APEXII DUO CCD area-detector diffractometer | 4628 independent reflections |
Radiation source: fine-focus sealed tube | 2976 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.034 |
φ and ω scans | θmax = 32.8°, θmin = 2.6° |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | h = −14→15 |
Tmin = 0.876, Tmax = 0.963 | k = −16→16 |
17572 measured reflections | l = −18→17 |
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)] = 0.047 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.139 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.04 | w = 1/[σ2(Fo2) + (0.0608P)2 + 0.1513P] where P = (Fo2 + 2Fc2)/3 |
4628 reflections | (Δ/σ)max < 0.001 |
176 parameters | Δρmax = 0.30 e Å−3 |
0 restraints | Δρmin = −0.31 e Å−3 |
C6H9N2+·C7H4ClO2− | V = 1265.84 (14) Å3 |
Mr = 264.70 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 9.8510 (6) Å | µ = 0.30 mm−1 |
b = 10.7707 (8) Å | T = 297 K |
c = 12.2123 (7) Å | 0.46 × 0.25 × 0.13 mm |
β = 102.335 (2)° |
Bruker SMART APEXII DUO CCD area-detector diffractometer | 4628 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | 2976 reflections with I > 2σ(I) |
Tmin = 0.876, Tmax = 0.963 | Rint = 0.034 |
17572 measured reflections |
R[F2 > 2σ(F2)] = 0.047 | 0 restraints |
wR(F2) = 0.139 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.04 | Δρmax = 0.30 e Å−3 |
4628 reflections | Δρmin = −0.31 e Å−3 |
176 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 | ||
Cl1 | −0.02173 (5) | 0.82984 (4) | 0.23669 (4) | 0.07093 (17) | |
O1 | 0.41482 (11) | 0.36071 (10) | 0.43150 (8) | 0.0468 (2) | |
O2 | 0.29316 (12) | 0.37788 (10) | 0.56405 (8) | 0.0521 (3) | |
N1 | 0.54982 (12) | 0.32374 (10) | 0.06443 (9) | 0.0384 (2) | |
N2 | 0.44920 (16) | 0.28252 (14) | 0.21480 (12) | 0.0534 (3) | |
C1 | 0.53584 (14) | 0.34947 (12) | 0.16960 (11) | 0.0393 (3) | |
C2 | 0.61705 (15) | 0.44688 (14) | 0.22692 (12) | 0.0462 (3) | |
H2A | 0.6104 | 0.4672 | 0.2996 | 0.055* | |
C3 | 0.70468 (15) | 0.51067 (14) | 0.17600 (13) | 0.0490 (3) | |
H3A | 0.7581 | 0.5743 | 0.2148 | 0.059* | |
C4 | 0.71723 (14) | 0.48309 (13) | 0.06545 (12) | 0.0452 (3) | |
C5 | 0.63774 (14) | 0.38868 (13) | 0.01390 (11) | 0.0416 (3) | |
H5A | 0.6435 | 0.3675 | −0.0588 | 0.050* | |
C6 | 0.81460 (18) | 0.55543 (18) | 0.01020 (17) | 0.0643 (4) | |
H6A | 0.8137 | 0.5209 | −0.0624 | 0.096* | |
H6B | 0.9070 | 0.5510 | 0.0555 | 0.096* | |
H6C | 0.7853 | 0.6406 | 0.0022 | 0.096* | |
C7 | 0.14475 (15) | 0.57790 (14) | 0.46421 (12) | 0.0449 (3) | |
H7A | 0.1323 | 0.5510 | 0.5338 | 0.054* | |
C8 | 0.06266 (16) | 0.67279 (15) | 0.40995 (14) | 0.0530 (4) | |
H8A | −0.0053 | 0.7091 | 0.4420 | 0.064* | |
C9 | 0.08322 (14) | 0.71276 (13) | 0.30744 (12) | 0.0452 (3) | |
C10 | 0.18420 (16) | 0.66134 (13) | 0.25949 (12) | 0.0452 (3) | |
H10A | 0.1978 | 0.6902 | 0.1909 | 0.054* | |
C11 | 0.26556 (14) | 0.56587 (12) | 0.31472 (11) | 0.0399 (3) | |
H11A | 0.3344 | 0.5309 | 0.2830 | 0.048* | |
C12 | 0.24526 (12) | 0.52207 (11) | 0.41692 (10) | 0.0336 (2) | |
C13 | 0.32454 (13) | 0.41235 (11) | 0.47546 (10) | 0.0356 (3) | |
H1N1 | 0.4981 (19) | 0.2561 (18) | 0.0206 (15) | 0.067 (5)* | |
H2N2 | 0.393 (2) | 0.227 (2) | 0.1687 (17) | 0.075 (6)* | |
H1N2 | 0.4328 (19) | 0.3062 (17) | 0.2770 (17) | 0.060 (5)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cl1 | 0.0665 (3) | 0.0571 (3) | 0.0817 (3) | 0.02362 (19) | −0.0011 (2) | 0.0172 (2) |
O1 | 0.0589 (6) | 0.0468 (5) | 0.0353 (5) | 0.0185 (4) | 0.0114 (4) | 0.0030 (4) |
O2 | 0.0713 (7) | 0.0503 (6) | 0.0373 (5) | 0.0150 (5) | 0.0171 (5) | 0.0093 (4) |
N1 | 0.0453 (6) | 0.0363 (5) | 0.0330 (5) | 0.0000 (4) | 0.0069 (4) | −0.0063 (4) |
N2 | 0.0695 (8) | 0.0554 (8) | 0.0388 (6) | −0.0138 (7) | 0.0196 (6) | −0.0123 (6) |
C1 | 0.0468 (7) | 0.0369 (6) | 0.0332 (6) | 0.0043 (5) | 0.0063 (5) | −0.0056 (5) |
C2 | 0.0529 (8) | 0.0457 (7) | 0.0384 (7) | 0.0010 (6) | 0.0060 (6) | −0.0134 (6) |
C3 | 0.0460 (7) | 0.0418 (7) | 0.0564 (8) | −0.0020 (6) | 0.0050 (6) | −0.0140 (6) |
C4 | 0.0424 (7) | 0.0400 (7) | 0.0532 (8) | 0.0028 (5) | 0.0102 (6) | −0.0018 (6) |
C5 | 0.0457 (7) | 0.0415 (7) | 0.0380 (6) | 0.0048 (5) | 0.0101 (5) | −0.0026 (5) |
C6 | 0.0588 (9) | 0.0611 (10) | 0.0768 (12) | −0.0101 (8) | 0.0231 (8) | −0.0026 (9) |
C7 | 0.0498 (7) | 0.0446 (7) | 0.0428 (7) | 0.0064 (6) | 0.0157 (6) | 0.0043 (6) |
C8 | 0.0503 (8) | 0.0513 (8) | 0.0608 (9) | 0.0148 (6) | 0.0195 (7) | 0.0036 (7) |
C9 | 0.0414 (7) | 0.0365 (6) | 0.0533 (8) | 0.0052 (5) | −0.0001 (6) | 0.0030 (6) |
C10 | 0.0534 (8) | 0.0405 (7) | 0.0408 (7) | 0.0040 (6) | 0.0083 (6) | 0.0073 (5) |
C11 | 0.0442 (6) | 0.0379 (6) | 0.0389 (6) | 0.0053 (5) | 0.0117 (5) | 0.0023 (5) |
C12 | 0.0365 (6) | 0.0295 (5) | 0.0330 (6) | −0.0017 (4) | 0.0036 (4) | −0.0022 (4) |
C13 | 0.0453 (6) | 0.0314 (6) | 0.0280 (5) | 0.0013 (5) | 0.0029 (5) | −0.0029 (4) |
Cl1—C9 | 1.7390 (14) | C5—H5A | 0.9300 |
O1—C13 | 1.2619 (16) | C6—H6A | 0.9600 |
O2—C13 | 1.2436 (16) | C6—H6B | 0.9600 |
N1—C1 | 1.3495 (16) | C6—H6C | 0.9600 |
N1—C5 | 1.3596 (18) | C7—C8 | 1.382 (2) |
N1—H1N1 | 0.98 (2) | C7—C12 | 1.3856 (18) |
N2—C1 | 1.3245 (19) | C7—H7A | 0.9300 |
N2—H2N2 | 0.92 (2) | C8—C9 | 1.379 (2) |
N2—H1N2 | 0.85 (2) | C8—H8A | 0.9300 |
C1—C2 | 1.4113 (19) | C9—C10 | 1.374 (2) |
C2—C3 | 1.354 (2) | C10—C11 | 1.3870 (18) |
C2—H2A | 0.9300 | C10—H10A | 0.9300 |
C3—C4 | 1.413 (2) | C11—C12 | 1.3881 (18) |
C3—H3A | 0.9300 | C11—H11A | 0.9300 |
C4—C5 | 1.3539 (19) | C12—C13 | 1.5097 (16) |
C4—C6 | 1.503 (2) | ||
C1—N1—C5 | 122.05 (12) | C4—C6—H6C | 109.5 |
C1—N1—H1N1 | 121.7 (10) | H6A—C6—H6C | 109.5 |
C5—N1—H1N1 | 116.2 (10) | H6B—C6—H6C | 109.5 |
C1—N2—H2N2 | 117.2 (12) | C8—C7—C12 | 121.22 (13) |
C1—N2—H1N2 | 118.2 (13) | C8—C7—H7A | 119.4 |
H2N2—N2—H1N2 | 122.3 (17) | C12—C7—H7A | 119.4 |
N2—C1—N1 | 119.39 (13) | C9—C8—C7 | 118.80 (13) |
N2—C1—C2 | 123.06 (13) | C9—C8—H8A | 120.6 |
N1—C1—C2 | 117.55 (13) | C7—C8—H8A | 120.6 |
C3—C2—C1 | 119.92 (13) | C10—C9—C8 | 121.41 (13) |
C3—C2—H2A | 120.0 | C10—C9—Cl1 | 119.23 (12) |
C1—C2—H2A | 120.0 | C8—C9—Cl1 | 119.36 (11) |
C2—C3—C4 | 121.78 (13) | C9—C10—C11 | 119.16 (13) |
C2—C3—H3A | 119.1 | C9—C10—H10A | 120.4 |
C4—C3—H3A | 119.1 | C11—C10—H10A | 120.4 |
C5—C4—C3 | 116.24 (13) | C10—C11—C12 | 120.66 (12) |
C5—C4—C6 | 122.81 (14) | C10—C11—H11A | 119.7 |
C3—C4—C6 | 120.95 (14) | C12—C11—H11A | 119.7 |
C4—C5—N1 | 122.46 (13) | C7—C12—C11 | 118.71 (12) |
C4—C5—H5A | 118.8 | C7—C12—C13 | 119.06 (11) |
N1—C5—H5A | 118.8 | C11—C12—C13 | 122.18 (11) |
C4—C6—H6A | 109.5 | O2—C13—O1 | 124.56 (12) |
C4—C6—H6B | 109.5 | O2—C13—C12 | 116.49 (11) |
H6A—C6—H6B | 109.5 | O1—C13—C12 | 118.93 (11) |
C5—N1—C1—N2 | −179.57 (13) | C7—C8—C9—Cl1 | 178.64 (12) |
C5—N1—C1—C2 | −0.37 (19) | C8—C9—C10—C11 | 1.0 (2) |
N2—C1—C2—C3 | 179.28 (15) | Cl1—C9—C10—C11 | −178.43 (11) |
N1—C1—C2—C3 | 0.1 (2) | C9—C10—C11—C12 | 0.3 (2) |
C1—C2—C3—C4 | 0.4 (2) | C8—C7—C12—C11 | 2.0 (2) |
C2—C3—C4—C5 | −0.6 (2) | C8—C7—C12—C13 | −175.35 (13) |
C2—C3—C4—C6 | 179.69 (15) | C10—C11—C12—C7 | −1.8 (2) |
C3—C4—C5—N1 | 0.3 (2) | C10—C11—C12—C13 | 175.48 (12) |
C6—C4—C5—N1 | −179.95 (14) | C7—C12—C13—O2 | 0.45 (17) |
C1—N1—C5—C4 | 0.1 (2) | C11—C12—C13—O2 | −176.81 (12) |
C12—C7—C8—C9 | −0.7 (2) | C7—C12—C13—O1 | 179.13 (12) |
C7—C8—C9—C10 | −0.8 (2) | C11—C12—C13—O1 | 1.87 (18) |
D—H···A | D—H | H···A | D···A | D—H···A |
N2—H1N2···O1 | 0.85 (2) | 2.02 (2) | 2.8654 (18) | 174.1 (19) |
N1—H1N1···O1i | 0.98 (2) | 1.75 (2) | 2.7255 (14) | 174.1 (16) |
N2—H2N2···O2i | 0.92 (2) | 1.83 (2) | 2.7437 (17) | 172.7 (18) |
C2—H2A···O2ii | 0.93 | 2.40 | 3.1459 (18) | 137 |
Symmetry codes: (i) x, −y+1/2, z−1/2; (ii) −x+1, −y+1, −z+1. |
Experimental details
Crystal data | |
Chemical formula | C6H9N2+·C7H4ClO2− |
Mr | 264.70 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 297 |
a, b, c (Å) | 9.8510 (6), 10.7707 (8), 12.2123 (7) |
β (°) | 102.335 (2) |
V (Å3) | 1265.84 (14) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.30 |
Crystal size (mm) | 0.46 × 0.25 × 0.13 |
Data collection | |
Diffractometer | Bruker SMART APEXII DUO CCD area-detector |
Absorption correction | Multi-scan (SADABS; Bruker, 2009) |
Tmin, Tmax | 0.876, 0.963 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 17572, 4628, 2976 |
Rint | 0.034 |
(sin θ/λ)max (Å−1) | 0.761 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.047, 0.139, 1.04 |
No. of reflections | 4628 |
No. of parameters | 176 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.30, −0.31 |
Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).
D—H···A | D—H | H···A | D···A | D—H···A |
N2—H1N2···O1 | 0.85 (2) | 2.02 (2) | 2.8654 (18) | 174.1 (19) |
N1—H1N1···O1i | 0.98 (2) | 1.75 (2) | 2.7255 (14) | 174.1 (16) |
N2—H2N2···O2i | 0.92 (2) | 1.83 (2) | 2.7437 (17) | 172.7 (18) |
C2—H2A···O2ii | 0.93 | 2.40 | 3.1459 (18) | 137 |
Symmetry codes: (i) x, −y+1/2, z−1/2; (ii) −x+1, −y+1, −z+1. |
Footnotes
‡Thomson Reuters ResearcherID: A-5599-2009.
Acknowledgements
The authors thank the Malaysian Government and Universiti Sains Malaysia (USM) for the research facilities and USM Short Term Grant No. 304/PFIZIK/6312078 to conduct this work. KT thanks The Academy of Sciences for the Developing World and USM for a TWAS–USM fellowship.
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In recent years, hydrogen bonds have attracted the interest of chemists and have been widely used to design and synthesize one, two and three-dimensional supramolecular compounds (Aakeroy et al., 2002). Pyridine and its derivatives play an important role in heterocyclic chemistry (Pozharski et al., 1997; Katritzky et al., 1996). They are often involved in hydrogen-bond interactions. 4-Chlorobenzoic acid (4-CBA) has been reported as intermediate product during biological or chemical degradation of pesticides and herbicides (Dionysiou et al., 2000). We have recently reported related crystal structures of 2-amino-5-methylpyridinium 3-chlorobenzoate (Thanigaimani et al., 2012a), 2-amino-5-methylpyridinium 2-aminobenzoate (Thanigaimani et al., 2012b) and 2-amino-5-methylpyridinium trifluoroacetate (Thanigaimani et al., 2012c). In order to study some interesting hydrogen bonding interactions of this compound, the synthesis and structure of the title salt is presented here.
The asymmetric unit (Fig. 1) contains one 2-amino-5-methylpyridinium cation and one 4-chlorobenzoate anion. The proton transfers from the carboxyl group oxygen atom (O1) to atom N1 of the 2-amino-5-methylpyrimidine resulted in the widening of C1—N1—C5 angle of the pyridinium ring to 122.06 (11)°, compared to the corresponding angle of 117.4 (3)° in neutral 2-amino-5-methylpyridine (Nahringbauer & Kvick, 1977). The 2-amino-5-methylpyridinium cation is essentially planar, with a maximum deviation of 0.005 (1) Å for atom C1. The carboxylate group of the 4-chlorobenzoate anion is slightly twisted from the attached ring with the dihedral angle between C7–C12 ring and O1/O2/C13 plane being 5.14 (16)°. The bond lengths (Allen et al., 1987) and angles are normal.
In the crystal packing (Fig. 2), the protonated N1 atom and a nitrogen atom of the 2-amino group (N2) are hydrogen-bonded to the carboxylate oxygen atoms (O1 and O2) via a pair of intermolecular N1—H1N1···O1i and N2—H2N2···O2i hydrogen bonds (symmetry code in Table 1), forming a ring motif of R22(8) (Bernstein et al., 1995). Furthermore, these motifs are connected via N2—H1N2···O1 and C2—H2A···O2ii hydrogen bonds to form a two-dimensional network parallel to the bc plane. The crystal structure is further stabilized by π–π interactions between the pyridine (C1–C5/N1) and benzene (C7–C12) rings, with centroid to centroid distance of 3.7948 (9) Å (symmetry codes: 1 - x, -1/2 + y, 1/2 - z and 1 - x, 1/2 + y, 1/2 - z)