4-Amino­pyridinium 4-nitro­benzoate 4-nitro­benzoic acid

Ching Kheng Quah; Samuel Robinson Jebas; Hoong-Kun Fun

doi:10.1107/S1600536808027761

. 2008 Sep 6;64(Pt 10):o1878–o1879. doi: 10.1107/S1600536808027761

4-Aminopyridinium 4-nitrobenzoate 4-nitrobenzoic acid

Ching Kheng Quah ^a, Samuel Robinson Jebas ^a,^‡, Hoong-Kun Fun ^a,^*

PMCID: PMC2959422 PMID: 21201092

Abstract

The asymmetric unit of the title compound, C₅H₇N₂ ⁺·C₇H₄NO₄ ⁻·C₇H₅NO₄, consists of an aminopyridinium cation, a 4-nitrobenzoate anion and a neutral 4-nitrobenzoic acid molecule. The pyridine ring forms dihedral angles of 64.70 (5)° and 70.37 (5)°, respectively, with the benzene rings of 4-nitrobenzoic acid and 4-nitrobenzoate. In the crystal structure, the cations, anions and the neutral 4-nitrobenzoic acid molecules are linked by O—H⋯O and N—H⋯O hydrogen bonds, forming a two-dimensional network parallel to (001). Adjacent networks are cross-linked via C—H⋯O hydrogen bonds and π–π stacking interactions [centroid–centroid distances 3.6339 (6) and 3.6566 (6) Å].

Related literature

For the biological activity of 4-aminopyridine, see: Judge et al. (2006 ▶); Schwid et al. (1997 ▶); Strupp et al. (2004 ▶). For related structures, see: Chao & Schempp (1977 ▶); Anderson et al. (2005 ▶); Andrau & White, (2003 ▶); Bhattacharya et al. (1994 ▶); Karle et al. (2003 ▶).

Experimental

Crystal data

C₅H₇N₂ ⁺·C₇H₄NO₄ ⁻·C₇H₅NO₄
M _r = 428.36
Triclinic,
a = 6.4561 (1) Å
b = 6.8598 (1) Å
c = 20.9055 (3) Å
α = 85.826 (1)°
β = 87.975 (1)°
γ = 86.188 (1)°
V = 920.92 (2) Å³
Z = 2
Mo Kα radiation
μ = 0.12 mm⁻¹
T = 100.0 (1) K
0.40 × 0.36 × 0.29 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.952, T _max = 0.965
24945 measured reflections
6647 independent reflections
5169 reflections with I > 2σ(I)
R _int = 0.031

Refinement

R[F ² > 2σ(F ²)] = 0.044
wR(F ²) = 0.132
S = 1.05
6647 reflections
284 parameters
1 restraint
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.43 e Å⁻³
Δρ_min = −0.39 e Å⁻³

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: APEX2; data reduction: SAINT (Bruker, 2005 ▶); 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, 2003 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808027761/ci2664sup1.cif

e-64-o1878-sup1.cif^{(21.4KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808027761/ci2664Isup2.hkl

e-64-o1878-Isup2.hkl^{(318.7KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3A—H1O3⋯O3Bⁱ	0.82	1.63	2.4457 (11)	170
N3—H3A⋯O3Bⁱⁱ	0.86	2.14	2.9977 (12)	172
N3—H3B⋯O4Bⁱ	0.86	2.07	2.8758 (12)	155
N2—H1N2⋯O4Aⁱⁱⁱ	0.85 (1)	1.99 (1)	2.7726 (12)	153 (1)
C2B—H2BA⋯O1B^iv	0.93	2.52	3.2187 (13)	133
C8—H8A⋯O3A^v	0.93	2.56	3.4565 (13)	161
C12—H12A⋯O1A^vi	0.93	2.55	3.4427 (13)	162

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) ; (vi) .

Acknowledgments

HKF and SRJ thank the Malaysian Government and Universiti Sains Malaysia for Science Fund grant No. 305/PFIZIK/613312. SRJ thanks Universiti Sains Malaysia for a post-doctoral research fellowship. CKQ thanks Universiti Sains Malaysia for a student assistanceship.

supplementary crystallographic information

Comment

4-Aminopyridine (Fampridine) is used clinically in Lambert-Eaton myasthenic syndrome and multiple sclerosis because by blocking potassium channels, it prolongs the action potentials thereby increasing transmitter release at the neuromuscular junction (Judge et al., 2006; Schwid et al., 1997; Strupp et al., 2004). The crystal structure of 4-aminopyridine has been reported (Chao & Schempp, 1977; Anderson et al., 2005). As an extension of our systematic study of hydrogen bonding patterns of 4-aminopyridine with aromatic carboxylic acids, we report here the crystal structure of the title compound.

The asymmetric unit of the title compound contains one 4-aminopyridinium cation, one 4-nitrobenzoate anion and one 4-nitrobenzoic acid molecule. A proton transfer from the carboxyl group of 4-nitrobenzoic acid to atom N2 of 4-aminopyridine resulted in the formation of ions. This lead to the widening of C8—N2—C12 angle of the pyridine ring to 120.86 (9)°, compared to 115.25 (13)° in the unprotonated 4-aminopyridine (Anderson et al., 2005). This type of protonation is observed in various 4-aminopyridine acid complexes (Bhattacharya et al., 1994; Karle et al., 2003). The bond lengths and angles of the 4-aminopyridne are comparable to the values reported earlier for 4-aminopyridine (Chao & Schempp, 1977; Anderson et al., 2005). The bond lengths and angles of the 4-nitrobenzoic acid is found to be normal(Andrau & White, 2003).

The dihedral angle between the benzene rings of 4-nitrobenzoic acid (C1A-C6A) and 4-nitrobenzoate (C1B-C6B) units is 6.62 (5)°. The pyridine (N2/C8—C12) ring forms dihedral angles of 64.70 (5)° and 70.37 (5)°, respectively, with the C1A-C6A and C1B-C6B rings.

In the crystal structure, the cations, anions and the neutral 4-nitrobenzoic acid molecules are linked to form a two-dimensional network (Fig. 2) parallel to the (0 0 1) by O—H···O and N—H···O hydrogen bonds (Table 1). The adjacent networks are cross-linked via C—H···O hydrogen bonds. The crystal packing is further consolidated by π–π stacking interactions between symmetry-related C1A-C6A (centroid Cg1) and C1B-C6B (centroid Cg2) rings, with Cg1···Cg1ⁱ and Cg2···Cg2^vii distances of 3.6566 (6) Å and 3.6339 (6) Å, respectively [symmetry codes: (i) 1-x, 2-y, 1-z; (vii) 2-x, 2-y, 2-z].

Experimental

4-Aminopyridine and 4-nitrobenzoic acid were mixed in equimolar ratio in methanol and warmed in a water bath for 2 h. Colourless single crystals were obtained after a week on slow evaporation.