2-Amino­pyridinium 1-phenyl­cyclo­propane-1-carboxyl­ate

Guangwen He; Srinivasulu Aitipamula; Pui Shan Chow; Reginald B H Tan

doi:10.1107/S1600536810049093

. 2010 Nov 27;66(Pt 12):o3339–o3340. doi: 10.1107/S1600536810049093

2-Aminopyridinium 1-phenylcyclopropane-1-carboxylate

Guangwen He ^a,^*, Srinivasulu Aitipamula ^a, Pui Shan Chow ^a, Reginald B H Tan ^a,^b,^*

PMCID: PMC3011640 PMID: 21589613

Abstract

In the title salt, C₅H₇N₂ ⁺·C₁₀H₉O₂ ⁻, 2-aminopyridine and 1-phenylcyclopropane-1-carboxylic acid crystallize together, forming a 2-aminopyridinium–carboxylate supramolecular heterosynthon involving two N—H⋯O hydrogen bonds, which in turn dimerizes to form a four-component supramolecular unit also sustained by N—H⋯O hydrogen bonding. A C—H⋯π interaction between a pyridine C—H group and the centroid of the phenyl ring of the anion further stabilizes the four-component supramolecular unit. The overall crystal packing also features C—H⋯O interactions.

Related literature

For structural studies of 2-aminopyridine, see: Chao et al. (1975 ▶). For recent molecular co-crystals and salts of 2-aminopyridine, see: Sivaramkumar et al. (2010 ▶); Chitra et al. (2008 ▶); Quah et al. (2008 ▶); Xie (2007 ▶); Li et al. (2006 ▶, 2007 ▶); Yang & Qu (2006 ▶); Bis & Zaworotko (2005 ▶). For the use of 2-aminopyridine in the synthesis of pharmaceuticals, see: O’Neil (2006 ▶). For our previous work on screening for molecular co-crystals and salts, see: He et al. (2009 ▶).

Experimental

Crystal data

C₅H₇N₂ ⁺·C₁₀H₉O₂ ⁻
M _r = 256.30
Triclinic,
a = 8.6147 (17) Å
b = 9.0555 (18) Å
c = 9.2346 (18) Å
α = 75.56 (3)°
β = 87.72 (3)°
γ = 72.79 (3)°
V = 666.0 (2) Å³
Z = 2
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 110 K
0.33 × 0.33 × 0.22 mm

Data collection

Rigaku Saturn CCD area-detector diffractometer
Absorption correction: multi-scan (Blessing, 1995 ▶) T _min = 0.972, T _max = 0.981
9557 measured reflections
3271 independent reflections
3103 reflections with I > 2σ(I)
R _int = 0.017

Refinement

R[F ² > 2σ(F ²)] = 0.052
wR(F ²) = 0.145
S = 1.12
3271 reflections
184 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.31 e Å⁻³
Δρ_min = −0.24 e Å⁻³

Data collection: CrystalClear (Rigaku, 2008 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: X-SEED (Barbour, 2001 ▶); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 ▶) and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810049093/ng5075sup1.cif

e-66-o3339-sup1.cif^{(17.4KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810049093/ng5075Isup2.hkl

e-66-o3339-Isup2.hkl^{(160.4KB, hkl)}

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

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

Cg1 is the centroid of the C10–C15 ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1⋯O1	0.983 (19)	1.64 (2)	2.6255 (15)	176.2 (17)
N2—H6⋯O2ⁱ	0.913 (18)	1.938 (18)	2.8230 (16)	162.6 (16)
N2—H9⋯O2	0.949 (19)	1.844 (19)	2.7903 (15)	175.2 (16)
C11—H11⋯O1ⁱⁱ	0.95	2.53	3.479 (2)	178
C12—H12⋯O1ⁱⁱⁱ	0.95	2.47	3.3212 (18)	149
C2—H2⋯Cg1ⁱ	0.95	2.62	3.5464 (15)	166

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

Acknowledgments

This work was supported by the Science and Engineering Research Council of A*STAR (Agency for Science, Technology and Research), Singapore.

supplementary crystallographic information

Comment

2-Aminopyridine is one of the three positional isomers of aminopyridine and is widely used as an intermediate in the synthesis of pharmaceuticals (O'Neil, 2006). We have chosen 2-aminopyridine and 1-phenylcyclopropane-1-carboxylic acid for cocrystallization experiment as an extension work to our previous study on screening for molecular cocrystals and salts (He et al., 2009).

The crystal structure of the title salt contains each one molecule of 2-aminopyridine and 1-phenylcyclopropane-1-carboxylic acid in the asymmetric unit (Fig. 2). Bis and Zaworotko revealed four types of two-point recognition possibilities in molecular complexes formed between 2-aminopyridine and carboxylic acids (Bis & Zaworotko, 2005). They have distinguished the type I–IV (Fig 1) synthons depending on whether the interacting complementary functional groups are the same or different. Type I involves formation of the carboxylic acid homosynthon; type II involves formation of the 2-aminopyridine homosynthon; type III and IV involve formation of 2-aminopyridine-carboxylic acid and 2-aminopyridinium-carboxylate supramolecular heterosynthons, respectively.

The title salt features type IV heterosynthon, where the 2-aminopyridinium ion forms a heterosynthon with the carboxylate group of the 1-phenylcyclopropane-1-carboxylate via two N–H···O (N···O = 2.6255 (15) and 2.7903 (15) Å) hydrogen bonds. Two such heterosynthons related by an inversion center dimerizes to form a four-component supramolecular unit sustained by N–H···O (N···O = 2.8230 (16) Å) hydrogen bonding (Fig. 3). The four-component supramolecular unit is further stabilized by a C–H···π interaction involving the 2-C–H of the pyridine ring and centroid of the phenyl ring of the carboxylate: C···Cg1 (1 - x,1 - y,1 - z) = 3.5464 (15) Å, where Cg1 denotes the centroid of the ring C10–C15 of 1-phenylcyclopropane-1-carboxylate (Fig. 4). Two prominent C–H···O interactions that involve the 11-C—H and 12-C—H of the phenyl ring of the 1-phenylcyclopropane-1-carboxylate and O1 of the same molecule at (-x + 1, -y + 1, -z + 2) and (x + 1, y, z), respectively, stabilize the overall crystal structure.

Experimental

0.1883 g (2 mmol) of 2-aminopyridine (Acros Organic, 99+%)) and 0.3246 g (2 mmol) of 1-phenylcyclopropane-1-carboxylic acid (Sigma, 97%) and were dissolved into 3 ml of ethyl acetate (Fisher Scientific, HPLC). Solution was then filtered through a 0.22µm PTFE filter. Filtered solution was finally sealed with Parafilm^? and small holes were made to allow solvent to slowly evaporate. The block-shaped crystal (0.33 × 0.33 × 0.22 mm) suitable for single-crystal X-ray diffraction was collected after one day.