3,4-Diamino­pyridinium 4-nitro­benzoate–4-nitro­benzoic acid (1/1)

Hoong-Kun Fun; Kasthuri Balasubramani

doi:10.1107/S1600536809027354

. 2009 Jul 18;65(Pt 8):o1887–o1888. doi: 10.1107/S1600536809027354

3,4-Diaminopyridinium 4-nitrobenzoate–4-nitrobenzoic acid (1/1)

Hoong-Kun Fun ^a,^*,^‡, Kasthuri Balasubramani ^a

PMCID: PMC2977481 PMID: 21583579

Abstract

In the title compound, C₅H₈N₃ ⁺·C₇H₄NO₄ ⁻·C₇H₅NO₄, the non-H atoms of the 3,4-diaminopyridinium cation are coplanar, with a maximum deviation of 0.022 (1) Å. The carboxylate and nitro groups of the 4-nitrobenzoate anion are twisted out of the attached ring planes by dihedral angles of 15.89 (8) and 10.20 (8)°, respectively. In the 4-nitrobenzoic acid molecule, the carboxyl and nitro groups form dihedral angles of 18.25 (8) and 6.55 (8)°, respectively, with the benzene ring. In the crystal, the constituent units form two-dimensional networks parallel to (001) by O—H⋯O, N—-H⋯O and C—H⋯O hydrogen bonds. Weak π–π interactions involving inversion-related 4-nitrobenzoic acid molecules [centroid–centroid distance = 3.7325 (8) Å] and inversion-related 4-nitrobenzoate molecules [centroid–centroid distance = 3.7124 (8) Å] are also observed.

Related literature

For general background to substituted pyridines, see: Pozharski et al. (1997 ▶); Katritzky et al. (1996 ▶); For related structures, see: Opozda et al. (2006 ▶); Rubin-Preminger & Englert (2007 ▶); Koleva et al. (2007 ▶, 2008 ▶); Fun & Balasubramani (2009 ▶). For bond-length data, see: Allen et al. (1987 ▶). For hydrogen-bond motifs, see: Bernstein et al. (1995 ▶). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986 ▶).

Experimental

Crystal data

C₅H₈N₃ ⁺·C₇H₄NO₄ ⁻·C₇H₅NO₄
M _r = 443.38
Triclinic,
a = 6.8073 (2) Å
b = 6.8087 (2) Å
c = 21.0171 (5) Å
α = 80.859 (1)°
β = 83.253 (1)°
γ = 78.549 (1)°
V = 938.88 (5) Å³
Z = 2
Mo Kα radiation
μ = 0.13 mm⁻¹
T = 100 K
0.56 × 0.20 × 0.17 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.934, T _max = 0.979
27907 measured reflections
5435 independent reflections
4025 reflections with I > 2σ(I)
R _int = 0.041

Refinement

R[F ² > 2σ(F ²)] = 0.059
wR(F ²) = 0.190
S = 1.05
5435 reflections
353 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.81 e Å⁻³
Δρ_min = −0.44 e Å⁻³

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

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809027354/ci2849sup1.cif

e-65-o1887-sup1.cif^{(21.8KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809027354/ci2849Isup2.hkl

e-65-o1887-Isup2.hkl^{(260.7KB, 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
O3B—H1O3⋯O3Aⁱ	0.82	1.65	2.463 (2)	173
N3—H1N3⋯O4Bⁱⁱ	1.05 (3)	2.08 (3)	3.008 (3)	146 (2)
N3—H2N3⋯O2Bⁱⁱⁱ	0.92 (3)	2.39 (3)	3.129 (2)	138 (2)
N2—H1N2⋯O3B^iv	1.00 (2)	2.00 (2)	2.929 (2)	154 (2)
N4—H1N4⋯O4Aⁱ	0.90 (2)	2.18 (2)	3.068 (2)	169 (2)
N4—H2N4⋯O3A^v	0.89 (2)	2.35 (2)	3.152 (2)	150 (2)
C1B—H1B⋯O4Bⁱⁱ	0.94 (2)	2.52 (2)	3.231 (2)	133 (2)
C4B—H4B⋯O1B^vi	0.97 (2)	2.54 (2)	3.250 (2)	130 (2)
C12—H12⋯O4B^vii	0.89 (2)	2.50 (2)	3.376 (2)	165 (2)

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

Acknowledgments

HKF and KB thank the Malaysian Government and Universiti Sains Malaysia for the Science Fund grant No. 305/PFIZIK/613312. KB thanks Universiti Sains Malaysia for a post–doctoral research fellowship. HKF also thanks Universiti Sains Malaysia for the Research University Golden Goose grant No. 1001/PFIZIK/811012.

supplementary crystallographic information

Comment

Pyridine and its derivatives play an important role in heterocyclic chemistry (Pozharski et al., 1997; Katritzky et al., 1996). 3,4-Diaminopyridine is used as a component in Schiff base reactions (Opozda et al., 2006). The crystal structure of 3,4-diaminopyridine (Rubin-Preminger & Englert, 2007), 3,4-diaminopyridinium hydrogen squarate (Koleva et al., 2007), 3,4-diaminopyridinium hydrogen tartarate (Koleva et al., 2008) and 3,4-diaminopyridinium hydrogen succinate (Fun & Balasubramani, 2009) have been reported. Since our aim is to study some interesting hydrogen-bonding interactions, the synthesis and structure of the title compound, (I), is presented here.

The asymmetric unit of (I) contains a 3,4-diaminopyridinium cation, a 4-nitrobenzoate anion and a 4-nitrobenzoic acid molecule (Fig 1). The bond lengths (Allen et al., 1987) and angles are normal.

In the 3,4-diaminopyridinium cation, the protonation of atom N2 has lead to a slight increase in C8—N2—C12 angle to 120.32 (15)° compared to 115.69 (19)° in 3,4-diaminopyridine (Rubin-Preminger & Englert, 2007). The non-H atoms of the 3,4-diaminopyridinium cation are coplanar, with a maximum deviation of 0.022 (1) Å for atom N4. The sum of bond angles associated with atoms N3 and N4 suggests that atom N3 is sp³ hybridized while atom N4 is sp² hybridized.

In the 4-nitrobenzoate anion, the carboxylate group is twisted slightly from the attached ring; the dihedral angle between C1A-C6A and O3A/O4A/C3A/C7A planes is 15.89 (8)°. The nitro group is twisted away from the attached benzene ring by 10.20 (8)°. In the neutral 4-nitrobenzoic acid molecule, the carboxylic acid (O3B/O4b/C3B/C7B) and nitro (O1B/O2B/N1B/C6B) groups form dihedral angles of 18.25 (8)° and 6.55 (8)°, respectively, with the attached C1B-C6B benzene ring.

The dihedral angle between the benzene rings of 4-nitrobenzoate (C1A-C6A) anion and 4-nitrobenzoic acid (C1B-C6B) molecule is 6.16 (6)°. The pyridine ring (N2/C8-C12) forms dihedral angles of 71.75 (8)° and 65.83 (8)°, respectively, with the C1A-C6A and C1B-C6B rings.

In the crystal packing (Fig. 2), the two amino groups (N3 and N4) are involved in N—H···O hydrogen bonding with two 4-nitrobenzoate O atoms (O3A and O4A), one 4-nitrobenzoic acid O atom (O4B) and with one nitro group O atom (O2B). The 4-nitrobenzoic acid hydrogen, H1O3, is hydrogen-bonded to the carboxylate oxygen atom of 4-nitrobenzoate through O—H···O bonds. The 4-nitrobenzoic acid carbon atoms (C1B & C4B) are involved in C—H···O hydrogen bonding with the carboxylic acid and nitro group O atoms O4B and O1B, to form an R₂²(10) ring motif (Bernstein et al., 1995). The O—H···O, N—H···O and C—H···O hydrogen bonds (Table 1) link all the constituent units to form a two-dimensional network parallel to the (001). The crystal structure is further stabilized by π-π interactions. The inversion related 4-nitrobenzoic acid molecules are stacked with a centroid-to-centroid distance of 3.7325 (8) Å. Similarly, the inversion related 4-nitrobenzoate molecules are stacked with a centroid-to-centroid distance of 3.7124 (8) Å.

Experimental

Hot methanol solutions (20 ml) of 3,4-diaminopyridine (27 mg, Aldrich) and 4-nitrobenzoic acid (42 mg, Merck) were mixed and warmed over a heating magnetic stirrer for 5 minutes. The resulting solution was allowed to cool slowly at room temperature. Crystals of (I) appeared from the mother liquor after a few days.