organic compounds
Bis(2-amino-5-methylpyridinium) fumarate–fumaric acid (1/1)
aX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia
*Correspondence e-mail: hkfun@usm.my
In the 6H9N2+·0.5C4H2O42−·0.5C4H6O4, the fumarate dianion and fumaric acid molecule are located on inversion centres. The 2-amino-5-methylpyrimidinium cation interacts with the carboxylate group of the fumarate anion through a pair of N—H⋯O hydrogen bonds, forming an R22(8) ring motif. These motifs are centrosymmetrically paired via N—H⋯O hydrogen bonds, forming a complementary DDAA array. The carboxyl groups of the fumaric acid molecules and the carboxylate groups of the fumarate anions are hydrogen bonded through O—H⋯O hydrogen bonds, leading to a supramolecular chain along [101]. The is further stabilized by weak C—H⋯O hydrogen bonds.
of the title compound, CRelated literature
For details of fumaric acid, see: Batchelor et al. (2000). For related structures, see: Hemamalini & Fun (2010a,b,c); Nahringbauer & Kvick (1977). For hydrogen-bond motifs, see: Bernstein et al. (1995). For DDAA arrays, see: Robert et al. (2001); Umadevi et al. (2002); Thanigaimani et al. (2007). For carboxyl–carboxylate interactions, see: Büyükgüngör & Odabaşoğlu (2002); Büyükgüngör et al. (2004). For bond-length data, see: Allen et al. (1987). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986).
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/S1600536810027960/is2576sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810027960/is2576Isup2.hkl
A hot methanol solution (20 ml) of 2-amino-5-methylpyridine (27 mg, Aldrich) and fumaric acid (29 mg, Merck) were mixed and warmed over a heating magnetic stirrer for a few minutes. The resulting solution was allowed to cool slowly at room temperature and crystals of the title compound appeared after a few days.
All hydrogen atoms were positioned geometrically (O—H = 0.82 Å, N—H = 0.86 Å and C—H = 0.93 or 0.96 Å) and were refined using a riding model, with Uiso(H) = 1.2 or 1.5Ueq(C). A rotating group model was used for the methyl group.
Recently we have reported the crystal structures of 2-amino-5-methylpyridinium 4-nitrobenzoate (Hemamalini & Fun, 2010a), 2-amino-5-methylpyridinium 3-aminobenzoate (Hemamalini & Fun, 2010c). and 2-amino-5-methylpyridinium nicotinate (Hemamalini & Fun, 2010b). Fumaric acid is of interest since it is known to form supramolecular assemblies with N-aromatic complexes (Batchelor et al., 2000). Herein we report the
and supramolecular patterns of the new compound containing pyridine derivative and fumaric acid components.The title compound (I) is shown in Fig. 1. The ═C double bond located at an inversion center. In the fumaric acid, the C7—O1 bond distance of 1.2118 (7) Å is much shorter than the C7—O2 bond distance of 1.3199 (7) Å suggesting that the carboxyl group is not deprotonated in the The 2-amino-5-methyl pyridinium cation is essentially planar with a maximum deviation of 0.011 (1) Å for atom N1. The 2-amino-5-methylpyridine is protonated at N1 which is evident from the increase in the internal angle at N1 (C1—N1—C5) from 117.4 (3)° in neutral 2-amino-5-methylpyridine (Nahringbauer & Kvick, 1977) to 123.03 (5)° in the present study. The bond lengths (Allen et al., 1987) and angles are within normal ranges.
contains one 2-amino-5-methylpyridinium cation, a half of the fumarate anion and a half of the fumaric acid molecule. The dihedral angles between pyridinium ring and the planes formed by the fumarate anion and fumaric acid molecule are 10.53 (2)° and 55.21 (2)°, respectively. The planar fumarate and fumaric acid molecule is centrosymmetric with the mid-point of the CIn the crystal packing (Fig. 2), the protonated N1 atom and the 2-amino group (N2) is hydrogen-bonded to the carboxylate oxygen atoms (O3 and O4) via a pair of intermolecular N1—H1···O4 and N2—H2A···O3 hydrogen bonds forming a ring motif R22(8) (Bernstein et al., 1995). These motifs are centrosymmetrically paired via N2—H2B···O3 hydrogen bonds to produce the DDAA (D = donor in hydrogen bonds, A = acceptor in hydrogen bonds) array of quadruple hydrogen bonds. This can be represented by the graph-set notation R22(8), R42(8) and R22(8) (Fig. 2). This type of array has also been identified in trimethoprim hydrogen glutarate (Robert et al., 2001), trimethoprim formate (Umadevi et al., 2002) and 2-amino-4,6-dimethoxypyridinium salicylate (Thanigaimani et al., 2007). The carboxyl groups of the fumaric acid molecules and the carboxylate groups of the fumarate anions are hydrogen bonded through O2—H2C···O4 hydrogen bonds leading to the formation of a one-dimensional hydrogen-bonded supramolecular chain along the [101] (Fig. 3). This type of carboxyl–carboxylate interaction has been reported in the crystal structures of 2-aminopyridinium–succinate –succinic acid (Büyükgüngör & Odabaşoğlu, 2002) and 2- aminopyridinium–fumarate–fumaric acid (Büyükgüngör et al., 2004). This chain can be designated by graph-set notation C22(14). The
is further stabilized by weak intermolecular C5—H5···O1 (Table 1) hydrogen bonds.For details of fumaric acid, see: Batchelor et al. (2000). For related structures, see: Hemamalini & Fun (2010a,b,c); Nahringbauer & Kvick (1977). For hydrogen-bond motifs, see: Bernstein et al. (1995). For DDAA arrays, see: Robert et al. (2001); Umadevi et al. (2002); Thanigaimani et al. (2007). For carboxyl–carboxylate interactions, see: Büyükgüngör & Odabaşoğlu (2002); Büyükgüngör et al. (2004). For bond-length data, see: Allen et al. (1987). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986).
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+·0.5C4H4O42−·0.5C4H2O4 | Z = 2 |
Mr = 224.22 | F(000) = 236 |
Triclinic, P1 | Dx = 1.423 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 4.0366 (4) Å | Cell parameters from 9900 reflections |
b = 9.3145 (10) Å | θ = 2.7–37.6° |
c = 14.0077 (14) Å | µ = 0.11 mm−1 |
α = 94.030 (3)° | T = 100 K |
β = 95.060 (3)° | Block, colourless |
γ = 90.903 (3)° | 0.61 × 0.22 × 0.20 mm |
V = 523.20 (9) Å3 |
Bruker APEXII DUO CCD area-detector diffractometer | 5445 independent reflections |
Radiation source: fine-focus sealed tube | 4852 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.019 |
φ and ω scans | θmax = 37.7°, θmin = 1.5° |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | h = −6→6 |
Tmin = 0.935, Tmax = 0.978 | k = −15→15 |
19772 measured reflections | l = −24→23 |
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)] = 0.036 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.110 | H-atom parameters constrained |
S = 1.05 | w = 1/[σ2(Fo2) + (0.0626P)2 + 0.0878P] where P = (Fo2 + 2Fc2)/3 |
5445 reflections | (Δ/σ)max = 0.001 |
147 parameters | Δρmax = 0.60 e Å−3 |
0 restraints | Δρmin = −0.34 e Å−3 |
C6H9N2+·0.5C4H4O42−·0.5C4H2O4 | γ = 90.903 (3)° |
Mr = 224.22 | V = 523.20 (9) Å3 |
Triclinic, P1 | Z = 2 |
a = 4.0366 (4) Å | Mo Kα radiation |
b = 9.3145 (10) Å | µ = 0.11 mm−1 |
c = 14.0077 (14) Å | T = 100 K |
α = 94.030 (3)° | 0.61 × 0.22 × 0.20 mm |
β = 95.060 (3)° |
Bruker APEXII DUO CCD area-detector diffractometer | 5445 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | 4852 reflections with I > 2σ(I) |
Tmin = 0.935, Tmax = 0.978 | Rint = 0.019 |
19772 measured reflections |
R[F2 > 2σ(F2)] = 0.036 | 0 restraints |
wR(F2) = 0.110 | H-atom parameters constrained |
S = 1.05 | Δρmax = 0.60 e Å−3 |
5445 reflections | Δρmin = −0.34 e Å−3 |
147 parameters |
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K. |
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 | ||
N1 | 0.64925 (12) | 0.45378 (5) | 0.20997 (3) | 0.01315 (8) | |
H1 | 0.5764 | 0.3700 | 0.1870 | 0.016* | |
N2 | 0.31601 (12) | 0.55122 (5) | 0.09009 (3) | 0.01504 (9) | |
H2A | 0.2404 | 0.4662 | 0.0712 | 0.018* | |
H2B | 0.2451 | 0.6241 | 0.0605 | 0.018* | |
C1 | 0.54215 (13) | 0.56996 (5) | 0.16485 (4) | 0.01190 (8) | |
C2 | 0.67623 (13) | 0.70674 (5) | 0.20110 (4) | 0.01341 (9) | |
H2 | 0.6147 | 0.7890 | 0.1706 | 0.016* | |
C3 | 0.89669 (13) | 0.71642 (6) | 0.28125 (4) | 0.01392 (9) | |
H3 | 0.9845 | 0.8062 | 0.3048 | 0.017* | |
C4 | 0.99507 (13) | 0.59304 (6) | 0.32951 (4) | 0.01383 (9) | |
C5 | 0.86767 (13) | 0.46307 (6) | 0.29027 (4) | 0.01433 (9) | |
H5 | 0.9311 | 0.3795 | 0.3189 | 0.017* | |
C6 | 1.21690 (15) | 0.60555 (7) | 0.42149 (4) | 0.01903 (10) | |
H6A | 1.1001 | 0.6517 | 0.4716 | 0.029* | |
H6B | 1.4123 | 0.6617 | 0.4131 | 0.029* | |
H6C | 1.2803 | 0.5112 | 0.4388 | 0.029* | |
O1 | 0.27081 (16) | 0.19332 (6) | 0.39352 (4) | 0.02686 (12) | |
O2 | 0.49662 (14) | 0.03168 (5) | 0.29314 (3) | 0.02170 (10) | |
H2C | 0.4257 | 0.0849 | 0.2522 | 0.033* | |
C7 | 0.42204 (15) | 0.08387 (6) | 0.37847 (4) | 0.01544 (9) | |
C8 | 0.54504 (15) | −0.00956 (6) | 0.45556 (4) | 0.01586 (9) | |
H8 | 0.6889 | −0.0833 | 0.4410 | 0.019* | |
O3 | 0.10076 (14) | 0.26911 (5) | 0.02053 (3) | 0.02176 (10) | |
O4 | 0.34405 (13) | 0.19338 (5) | 0.15605 (3) | 0.02015 (10) | |
C9 | 0.17514 (14) | 0.17185 (6) | 0.07482 (4) | 0.01450 (9) | |
C10 | 0.06922 (15) | 0.01973 (6) | 0.04396 (4) | 0.01504 (9) | |
H10 | 0.1014 | −0.0501 | 0.0880 | 0.018* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.01540 (17) | 0.00928 (16) | 0.01454 (17) | 0.00050 (13) | −0.00023 (13) | 0.00127 (13) |
N2 | 0.01861 (19) | 0.01217 (18) | 0.01362 (17) | 0.00003 (14) | −0.00253 (14) | 0.00090 (14) |
C1 | 0.01360 (18) | 0.01021 (18) | 0.01198 (18) | 0.00080 (14) | 0.00146 (14) | 0.00086 (14) |
C2 | 0.0165 (2) | 0.00966 (18) | 0.01402 (19) | 0.00031 (15) | 0.00102 (15) | 0.00067 (14) |
C3 | 0.01491 (19) | 0.01202 (19) | 0.01459 (19) | −0.00112 (15) | 0.00159 (15) | −0.00077 (15) |
C4 | 0.01274 (18) | 0.0149 (2) | 0.01376 (19) | 0.00020 (15) | 0.00090 (14) | 0.00098 (15) |
C5 | 0.01445 (19) | 0.0131 (2) | 0.0155 (2) | 0.00149 (15) | −0.00004 (15) | 0.00273 (15) |
C6 | 0.0157 (2) | 0.0245 (3) | 0.0163 (2) | −0.00173 (18) | −0.00234 (16) | 0.00247 (19) |
O1 | 0.0431 (3) | 0.0210 (2) | 0.01696 (19) | 0.0171 (2) | 0.00033 (18) | 0.00395 (16) |
O2 | 0.0396 (3) | 0.01464 (18) | 0.01119 (16) | 0.00699 (17) | 0.00121 (16) | 0.00307 (13) |
C7 | 0.0220 (2) | 0.01199 (19) | 0.01201 (18) | 0.00230 (16) | −0.00174 (16) | 0.00234 (15) |
C8 | 0.0221 (2) | 0.0134 (2) | 0.01226 (19) | 0.00444 (17) | −0.00012 (16) | 0.00316 (15) |
O3 | 0.0348 (2) | 0.01109 (17) | 0.01746 (18) | −0.00270 (15) | −0.01071 (16) | 0.00485 (14) |
O4 | 0.0338 (2) | 0.01254 (17) | 0.01229 (16) | −0.00547 (15) | −0.00885 (15) | 0.00302 (13) |
C9 | 0.0213 (2) | 0.01004 (18) | 0.01138 (18) | −0.00190 (15) | −0.00325 (15) | 0.00168 (14) |
C10 | 0.0219 (2) | 0.01007 (18) | 0.01231 (19) | −0.00229 (16) | −0.00368 (15) | 0.00215 (14) |
N1—C1 | 1.3492 (7) | C6—H6A | 0.9600 |
N1—C5 | 1.3635 (7) | C6—H6B | 0.9600 |
N1—H1 | 0.8600 | C6—H6C | 0.9600 |
N2—C1 | 1.3271 (7) | O1—C7 | 1.2118 (7) |
N2—H2A | 0.8600 | O2—C7 | 1.3199 (7) |
N2—H2B | 0.8600 | O2—H2C | 0.8200 |
C1—C2 | 1.4188 (8) | C7—C8 | 1.4903 (7) |
C2—C3 | 1.3665 (7) | C8—C8i | 1.3285 (11) |
C2—H2 | 0.9300 | C8—H8 | 0.9300 |
C3—C4 | 1.4184 (8) | O3—C9 | 1.2468 (7) |
C3—H3 | 0.9300 | O4—C9 | 1.2754 (6) |
C4—C5 | 1.3671 (8) | C9—C10 | 1.4965 (8) |
C4—C6 | 1.4992 (8) | C10—C10ii | 1.3314 (10) |
C5—H5 | 0.9300 | C10—H10 | 0.9300 |
C1—N1—C5 | 123.03 (5) | C4—C5—H5 | 119.4 |
C1—N1—H1 | 118.5 | C4—C6—H6A | 109.5 |
C5—N1—H1 | 118.5 | C4—C6—H6B | 109.5 |
C1—N2—H2A | 120.0 | H6A—C6—H6B | 109.5 |
C1—N2—H2B | 120.0 | C4—C6—H6C | 109.5 |
H2A—N2—H2B | 120.0 | H6A—C6—H6C | 109.5 |
N2—C1—N1 | 118.82 (5) | H6B—C6—H6C | 109.5 |
N2—C1—C2 | 123.44 (5) | C7—O2—H2C | 109.5 |
N1—C1—C2 | 117.73 (5) | O1—C7—O2 | 125.02 (5) |
C3—C2—C1 | 119.37 (5) | O1—C7—C8 | 123.42 (5) |
C3—C2—H2 | 120.3 | O2—C7—C8 | 111.56 (5) |
C1—C2—H2 | 120.3 | C8i—C8—C7 | 121.87 (6) |
C2—C3—C4 | 121.69 (5) | C8i—C8—H8 | 119.1 |
C2—C3—H3 | 119.2 | C7—C8—H8 | 119.1 |
C4—C3—H3 | 119.2 | O3—C9—O4 | 123.73 (5) |
C5—C4—C3 | 116.88 (5) | O3—C9—C10 | 119.39 (5) |
C5—C4—C6 | 121.66 (5) | O4—C9—C10 | 116.87 (4) |
C3—C4—C6 | 121.41 (5) | C10ii—C10—C9 | 122.67 (6) |
N1—C5—C4 | 121.22 (5) | C10ii—C10—H10 | 118.7 |
N1—C5—H5 | 119.4 | C9—C10—H10 | 118.7 |
C5—N1—C1—N2 | −176.50 (5) | C1—N1—C5—C4 | −0.74 (8) |
C5—N1—C1—C2 | 2.78 (8) | C3—C4—C5—N1 | −1.74 (8) |
N2—C1—C2—C3 | 176.95 (5) | C6—C4—C5—N1 | 175.74 (5) |
N1—C1—C2—C3 | −2.29 (8) | O1—C7—C8—C8i | 10.08 (12) |
C1—C2—C3—C4 | −0.13 (8) | O2—C7—C8—C8i | −169.47 (8) |
C2—C3—C4—C5 | 2.14 (8) | O3—C9—C10—C10ii | 7.89 (11) |
C2—C3—C4—C6 | −175.35 (5) | O4—C9—C10—C10ii | −170.95 (8) |
Symmetry codes: (i) −x+1, −y, −z+1; (ii) −x, −y, −z. |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O4 | 0.86 | 1.89 | 2.7305 (7) | 167 |
N2—H2A···O3 | 0.86 | 1.98 | 2.8334 (7) | 175 |
N2—H2B···O3iii | 0.86 | 2.04 | 2.8329 (7) | 154 |
O2—H2C···O4 | 0.82 | 1.75 | 2.5618 (7) | 170 |
C5—H5···O1iv | 0.93 | 2.46 | 3.3582 (9) | 162 |
Symmetry codes: (iii) −x, −y+1, −z; (iv) x+1, y, z. |
Experimental details
Crystal data | |
Chemical formula | C6H9N2+·0.5C4H4O42−·0.5C4H2O4 |
Mr | 224.22 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 100 |
a, b, c (Å) | 4.0366 (4), 9.3145 (10), 14.0077 (14) |
α, β, γ (°) | 94.030 (3), 95.060 (3), 90.903 (3) |
V (Å3) | 523.20 (9) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.11 |
Crystal size (mm) | 0.61 × 0.22 × 0.20 |
Data collection | |
Diffractometer | Bruker APEXII DUO CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2009) |
Tmin, Tmax | 0.935, 0.978 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 19772, 5445, 4852 |
Rint | 0.019 |
(sin θ/λ)max (Å−1) | 0.860 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.036, 0.110, 1.05 |
No. of reflections | 5445 |
No. of parameters | 147 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.60, −0.34 |
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 |
N1—H1···O4 | 0.8600 | 1.8900 | 2.7305 (7) | 167.00 |
N2—H2A···O3 | 0.8600 | 1.9800 | 2.8334 (7) | 175.00 |
N2—H2B···O3i | 0.8600 | 2.0400 | 2.8329 (7) | 154.00 |
O2—H2C···O4 | 0.8200 | 1.7500 | 2.5618 (7) | 170.00 |
C5—H5···O1ii | 0.9300 | 2.4600 | 3.3582 (9) | 162.00 |
Symmetry codes: (i) −x, −y+1, −z; (ii) x+1, y, z. |
Footnotes
‡Thomson Reuters ResearcherID: A-3561-2009
Acknowledgements
MH and HKF thank the Malaysian Government and Universiti Sains Malaysia for the Research University Golden Goose grant No. 1001/PFIZIK/811012. MH also thanks Universiti Sains Malaysia for a post-doctoral research fellowship.
References
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Recently we have reported the crystal structures of 2-amino-5-methylpyridinium 4-nitrobenzoate (Hemamalini & Fun, 2010a), 2-amino-5-methylpyridinium 3-aminobenzoate (Hemamalini & Fun, 2010c). and 2-amino-5-methylpyridinium nicotinate (Hemamalini & Fun, 2010b). Fumaric acid is of interest since it is known to form supramolecular assemblies with N-aromatic complexes (Batchelor et al., 2000). Herein we report the crystal structure and supramolecular patterns of the new compound containing pyridine derivative and fumaric acid components.
The title compound (I) is shown in Fig. 1. The asymmetric unit contains one 2-amino-5-methylpyridinium cation, a half of the fumarate anion and a half of the fumaric acid molecule. The dihedral angles between pyridinium ring and the planes formed by the fumarate anion and fumaric acid molecule are 10.53 (2)° and 55.21 (2)°, respectively. The planar fumarate and fumaric acid molecule is centrosymmetric with the mid-point of the C═C double bond located at an inversion center. In the fumaric acid, the C7—O1 bond distance of 1.2118 (7) Å is much shorter than the C7—O2 bond distance of 1.3199 (7) Å suggesting that the carboxyl group is not deprotonated in the crystal structure. The 2-amino-5-methyl pyridinium cation is essentially planar with a maximum deviation of 0.011 (1) Å for atom N1. The 2-amino-5-methylpyridine is protonated at N1 which is evident from the increase in the internal angle at N1 (C1—N1—C5) from 117.4 (3)° in neutral 2-amino-5-methylpyridine (Nahringbauer & Kvick, 1977) to 123.03 (5)° in the present study. The bond lengths (Allen et al., 1987) and angles are within normal ranges.
In the crystal packing (Fig. 2), the protonated N1 atom and the 2-amino group (N2) is hydrogen-bonded to the carboxylate oxygen atoms (O3 and O4) via a pair of intermolecular N1—H1···O4 and N2—H2A···O3 hydrogen bonds forming a ring motif R22(8) (Bernstein et al., 1995). These motifs are centrosymmetrically paired via N2—H2B···O3 hydrogen bonds to produce the DDAA (D = donor in hydrogen bonds, A = acceptor in hydrogen bonds) array of quadruple hydrogen bonds. This can be represented by the graph-set notation R22(8), R42(8) and R22(8) (Fig. 2). This type of array has also been identified in trimethoprim hydrogen glutarate (Robert et al., 2001), trimethoprim formate (Umadevi et al., 2002) and 2-amino-4,6-dimethoxypyridinium salicylate (Thanigaimani et al., 2007). The carboxyl groups of the fumaric acid molecules and the carboxylate groups of the fumarate anions are hydrogen bonded through O2—H2C···O4 hydrogen bonds leading to the formation of a one-dimensional hydrogen-bonded supramolecular chain along the [101] (Fig. 3). This type of carboxyl–carboxylate interaction has been reported in the crystal structures of 2-aminopyridinium–succinate –succinic acid (Büyükgüngör & Odabaşoğlu, 2002) and 2- aminopyridinium–fumarate–fumaric acid (Büyükgüngör et al., 2004). This chain can be designated by graph-set notation C22(14). The crystal structure is further stabilized by weak intermolecular C5—H5···O1 (Table 1) hydrogen bonds.