Enrofloxacinium picrate

Jerry P Jasinski; Ray J Butcher; M S Siddegowda; H S Yathirajan; B P Siddaraju

doi:10.1107/S160053681100170X

. 2011 Jan 22;67(Pt 2):o432–o433. doi: 10.1107/S160053681100170X

Enrofloxacinium picrate

Jerry P Jasinski ^a,^*, Ray J Butcher ^b, M S Siddegowda ^c, H S Yathirajan ^c, B P Siddaraju ^c

PMCID: PMC3051675 PMID: 21523099

Abstract

There is one cation–anion pair in the asymmetric unit of the title compound [systematic name: 4-(3-carboxy-6-fluoro-4-oxo-1,4-dihydroquinolin-7-yl)-1-ethylpiperazin-1-ium 2,4,6-trinitrophenolate], C₁₉H₂₃FN₃O₃ ⁺·C₆H₂N₃O₇ ⁻. The six-membered piperazine group in the cation adopts a slightly distorted chair conformation and contains a protonated N atom. The dihedral angles between the mean planes of the cyclopropyl and piperazine rings in the cation with the 10-atom ring system of the quinolone group are 48.1 (1) and 69.9 (5)°, respectively. The picrate anion interacts with the protonated N atom of an adjacent cation through a bifurcated N—H⋯O three-center hydrogen bond, forming an R ₁ ²(6) ring motif. Furthermore, there is an intramolecular O—H⋯O hydrogen bond. The dihedral angle between the mean planes of the anion benzene and cation piperizine, quinoline and cyclopropyl rings are 61.3 (6), 31.1 (4) and 70.4 (9)°, respectively. The mean planes of the two o-NO₂ and single p-NO₂ groups in the picrate anion are twisted by 6.7 (6), 38.3 (9) and 12.8 (7)° with respect to the mean plane of the benzene ring. Strong N—H⋯O and weak intermolecular C—H⋯O hydrogen bonds in concert with weak π–π stacking interactions [centroid–centroid distances = 3.5785 (13), 3.7451 (12) and 3.6587 (13) Å] dominate the crystal packing.

Related literature

For background to fluoroquinolones, see: Bhanot et al. (2001 ▶); Scholar (2003 ▶). For related structures, see: Hu & Yu, (2005 ▶); Jasinski et al. (2009 ▶, 2010a ▶, 2010b ▶); Recillas-Mota et al. (2007 ▶); Sun et al. (2004 ▶); Wang et al. (2005 ▶); Zou et al. (2005 ▶). For puckering parameters, see: Cremer & Pople (1975 ▶). For standard bond lengths, see: Allen et al. (1987) ▶.

Experimental

Crystal data

C₁₉H₂₃FN₃O₃ ⁺·C₆H₂N₃O₇ ⁻
M _r = 588.51
Triclinic,
a = 7.2111 (7) Å
b = 12.5766 (7) Å
c = 16.2362 (4) Å
α = 105.556 (2)°
β = 96.367 (6)°
γ = 96.223 (7)°
V = 1395.04 (16) Å³
Z = 2
Cu Kα radiation
μ = 0.98 mm⁻¹
T = 295 K
0.44 × 0.31 × 0.12 mm

Data collection

Oxford Diffraction Xcalibur Ruby Gemini diffractometer
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2007 ▶) T _min = 0.896, T _max = 1.000
9440 measured reflections
5437 independent reflections
3425 reflections with I > 2σ(I)
R _int = 0.032

Refinement

R[F ² > 2σ(F ²)] = 0.055
wR(F ²) = 0.177
S = 1.00
5437 reflections
382 parameters
H-atom parameters constrained
Δρ_max = 0.20 e Å⁻³
Δρ_min = −0.20 e Å⁻³

Data collection: CrysAlis PRO (Oxford Diffraction, 2007 ▶); cell refinement: CrysAlis PRO; data reduction: CrysAlis RED (Oxford Diffraction, 2007 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S160053681100170X/bt5451sup1.cif

e-67-0o432-sup1.cif^{(26.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S160053681100170X/bt5451Isup2.hkl

e-67-0o432-Isup2.hkl^{(266.2KB, 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
O2—H2⋯O3	0.82	1.78	2.536 (3)	151
N3—H3A⋯O1A	0.91	1.87	2.724 (3)	155
N3—H3A⋯O7A	0.91	2.38	3.024 (3)	128
C11—H11A⋯O3ⁱ	0.98	2.55	3.385 (3)	144
C15—H15B⋯O1ⁱⁱ	0.97	2.35	3.312 (3)	169
C17—H17B⋯O3Aⁱⁱⁱ	0.97	2.56	3.458 (4)	154
C3A—H3AA⋯O3^iv	0.93	2.55	3.331 (3)	142
C9—H9A⋯O4A^v	0.93	2.58	3.495 (3)	170
C14—H14B⋯O5A^vi	0.97	2.60	3.517 (4)	157
C18—H18A⋯O5A^vii	0.97	2.50	3.451 (5)	167

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

Acknowledgments

MSS thanks the University of Mysore for the research facilities and HSY thanks the UOM for sabbatical leave. RJB acknowledges the NSF MRI program (grant No. CHE-0619278) for funds to purchase an X-ray diffractometer.

supplementary crystallographic information

Comment

Enrofloxacin is a fluoroquinolone antibiotic and is a synthetic chemotherapeutic agent from the class of the fluoroquinolone carboxylic acid derivatives. It is sold by the Bayer Corporation under the trade name Baytril and has antibacterial activity against a broad spectrum of Gram-negative and Gram-positive bacteria. Its mechanism of action is not thoroughly understood, but it is believed to act by inhibiting bacterial DNA gyrase (a type-II topoisomerase), thereby preventing DNA supercoiling and DNA synthesis. The chemical and biological aspects of fluoroquinolones is described (Bhanot et al., 2001; Scholar, 2003). The crystal structure of norfloxacin hydrochloride (Zou et al., 2005) and norfloxacin methanol solvate (Wang et al., 2005) have already been reported. The crystal structure of a copper complex of enrofloxacin (Recillas-Mota et al., 2007), norfloxacin picrate (Hu & Yu, 2005) and 2-hydroxyethanaminium enrofloxacinate (Sun et al., 2004) are reported. Recently, the crystal structures of propiverine picrate (Jasinski et al., 2009), imatinibium dipicrate (Jasinski et al., 2010a) and chlorimipraminium picrate (Jasinski et al., 2010b) have been reported. In continuation of our work on picrates of biologically active compounds, this paper reports the crystal structure of C₁₉H₂₂FN₃O₃⁺ . C₆H₂N₃O₇^- obtained by the interaction of picric acid and enrofloxacin.

In the crystal structure of the title compound, (I), there is one cation-anion pair in the asymmetric unit (Fig. 1). One N atom in the 6-membered piperazine ring (N2/C14/C15/N3/C16/C17) in the enrofloxacinium cation is protonated which adopts a slightly distorted chair conformation with puckering parameters Q, θ and φ of 0.563 (3)A%, 4.0 (3)° and 358.0 (5)° (Cremer & Pople, 1975). The dihedral angles between the mean planes of the cyclopropyl and piperazine rings with the 10-atom ring system of the quinolone group are 48.1 (1)° and 69.9 (5)°, respectively. The picrate anion interacts with the protonated N atom of an adjacent cation through a bifurcated N—H···O three-center hydrogen bond forming a R₁²(6) ring motif. The dihedral angle between the mean planes of the anion benzene and cation piperizine, quinoline and cyclopropyl rings are 61.3 (6)°, 31.1 (4)° and 70.4 (9)°, respectively. The mean planes of the two o-NO₂ and single p-NO₂ groups in the picrate anion are twisted by 6.7 (6)°, 38.3 (9)° and 12.8 (7)° with respect to the mean planes of the 6-membered benzene ring. Bond distances and angles are in normal ranges (Allen et al., 1987). Strong N—H···O and weak intermolecular C—H···O hydrogen bonds in concert with weak π–π stacking interactions (Table 2) dominate the crystal packing creating a 2-D network structure along 011 (Fig. 2).

Experimental

Enrofloxacin (3.59 g, 0.1 mol) and picric acid (2.99 g, 0.1 mol) were dissolved in a mixture of acetonitrile and dimethyl sulfoxide (80:20 v/v). The solution was stirred for 15 min over a heating magnetic stirrer at 333 K. The resulting solution was kept aside at room temperature. After few days, X-ray quality crystals of the title compound were grown by slow evaporation (m.p.: 490 – 493 K).