Home Physical Sciences The crystal structure of 4-(3-carboxy-1-ethyl-6-fluoro-4-oxo-1,4-dihydroquinolin-7-yl)piperazin-1-ium 4-hydroxy-3,5-dimethoxybenzoate monohydrate, C25H30FN3O9
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The crystal structure of 4-(3-carboxy-1-ethyl-6-fluoro-4-oxo-1,4-dihydroquinolin-7-yl)piperazin-1-ium 4-hydroxy-3,5-dimethoxybenzoate monohydrate, C25H30FN3O9

  • Xuan-Ang Li and Cheng-Jun Jiang ORCID logo EMAIL logo
Published/Copyright: April 15, 2025

Abstract

C25H30FN3O9, monoclinic, P21/n, a = 16.3585(4) Å, b = 7.8763(2) Å, c = 18.7735(4) Å, ꞵ = 90.5690(10)°, V = 2418.74(10) Å3, Z = 4, Rgt (F) = 0.0410, wR ref (F2) = 0.1055, T = 170 K.

CCDC no.: 2361145

The molecular structure is shown in the figure. Table 1 contains the crystallographic data. The list of the atoms including atomic coordinates and displacement parameters can be found in the cif-file attached to this article.

Table 1:

Data collection and handling.

Crystal: Colourless block
Size 0.42 × 0.20 × 0.15 mm
Wavelength: Mo Kα radiation (0.71073 Å)
μ: 0.12 mm−1
Diffractometer, scan mode: Bruker D8 Venture, φ and ω scans
θmax, completeness: 28.3°, 100 %
N(hkl)measured, N(hkl)unique, Rint: 42,141, 5,967, 0.038
Criterion for Iobs, N(hkl)gt: Iobs > 2 σ(Iobs), 5094
N(param)refined: 351
Programs: Bruker, 1 Olex2, 2 SHELX 3 , 4

1 Source of materials

Equimolar quantities of norfloxacin (0.032 g) and syringic acid (0.020 g) in a 10 mL glass vial. The solid mixture was subsequently treated with a binary solvent system consisting of deionized water (2 mL) and absolute ethanol (2 mL). The mixture was transferred to a temperature -controlled magnetic stirring apparatus and gradually heated to 30 °C under gentle agitation (200 rpm) until complete dissolution was achieved. Through controlled solvent evaporation, the system was maintained in a metastable supersaturated state for 24 h to facilitate crystal nucleation and growth. The resulting suspension was vacuum-filtered through a Büchner funnel to isolate the crystalline product. The obtained compound was characterized as 4-(3-carboxy-1-ethyl-6-fluoro-4-oxo-1,4-dihydroquinolin-7-yl)piperazin-1-ium 4-hydroxy-3,5-dimethoxybenzoate monohydrate.

2 Experimental details

Absorption corrections were applied by using multi-scan program. 1 Using Olex2, 2 the structure was solved with the ShelXT 3 structure solution program using Intrinsic Phasing and refined with the ShelXL 4 refinement package using Least Squares minimisation. The H atoms were fixed, fixed Uiso were set to 1.2 times of all C(H) groups, C(H,H) groups and N(H,H) groups; 1.5 times of C(H,H,H,H) groups, O(H) groups and O(H,H) groups.

3 Comment

Norfloxacin, a fluoroquinolone antibacterial agent, is widely employed in treating infections caused by Gram-positive and Gram-negative bacteria. 5 Like other fluoroquinolones, its aqueous solubility exhibits a pronounced pH-dependent profile due to zwitterion formation via proton transfer between the carboxylic acid group and the basic piperazine ring. 6 At physiological pH, norfloxacin suffers from limited solubility and poor permeability, classifying it as a Biopharmaceutics Classification System (BCS) Class IV drug with inherently low bioavailability. 7 To address these limitations, pharmaceutical salt/cocrystal engineering has emerged as a strategic approach, wherein pairing the drug with a pharmaceutically acceptable counterion can modulate its physicochemical properties. 8 Previous studies have demonstrated the efficacy of salt formation with organic acids in enhancing norfloxacin’s solubility and dissolution performance. 9 , 10 , 11 In this study, we successfully designed, synthesized, and structurally characterized a novel norfloxacin-syringic acid salt. The asymmetric unit of the crystal structure [norfloxacin⋯syringic acid⋯H2O] comprises one norfloxacin cation, one syringic acid anion, and one water molecule. Key structural features include: A classical N–H⋯O hydro gen bond formed between the N1H1A moiety of the piperazine group and the O4 oxygen atom of syringic acid. Hydration-mediated interactions where the O9–H9A group of water forms hydrogen bonds with the O5 oxygen atom of syringic acid. The crystal packing exhibits a distinctive two-fold screw symmetry along the [0 1 0] axis, with screw components positioned at (¼, y, ¼). This symmetry element contributes to the three dimensional network formation through systematic molecular repetition.


Corresponding author: Cheng-Jun Jiang, School of Biological and Chemical Engineering, Zhejiang University of Science and Technology, Hangzhou, Liuhe Road 318#, China, E-mail:

Acknowledgments

We would also like to thank Mr Jiyong Liu from the Chemistry Instrumentation Center Zhejiang University for X-ray crystallographic analysis.

References

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Received: 2025-02-24
Accepted: 2025-04-02
Published Online: 2025-04-15
Published in Print: 2025-06-26

© 2025 the author(s), published by De Gruyter, Berlin/Boston

This work is licensed under the Creative Commons Attribution 4.0 International License.

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