Packing Interactions in Hydrated and Anhydrous Forms of the Antibiotic Ciprofloxacin: a Solid-State NMR, X-ray Diffraction, and Computer Simulation Study


We present an experimental NMR, X-ray diffraction (XRD), and computational study of the supramolecular assemblies of two crystalline forms of Ciprofloxacin: one anhydrate and one hydrate forming water wormholes. The resonance assignment of up to 51 and 54 distinct C-13 and H-1 resonances for the hydrate is reported. The effect of crystal packing, identified by XRD, on the H-1 and C-13 chemical shifts including weak interionic H-bonds, is quantified; H-1 chemical shift changes up to similar to-3.5 ppm for CH center dot center dot center dot pi contacts and similar to+2 ppm (CH center dot center dot center dot O(-)); similar to+4.7 ppm ((+)NH center dot center dot center dot O(-)) for H-bonds. Water intake induces chemical shift changes up to 2 and 5 ppm for H-1 and C-13 nuclei, respectively. Such chemical shifts are found to be sensitive detectors of hydration/dehydration in highly insoluble hydrates.



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Mafra, L; Santos, SM; Siegel, R; Alves, I; Paz, FAA; Dudenko, D; Spiess, HW

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The authors thank Fundacao para a Ciencia e a Tecnologia (FCT) for continued funding of the project PTDC/QUIQUI/100998/2008 and the Portuguese National NMR Network (RNRMN). The postdoc grants to S.S. and R.S. are also acknowledged. We thank CICECO (Univ. Aveiro), POCTI, FEDER, and FSE. L.M. greatly acknowledges the Max-Planck Society for funding. We also thank Lyndon Emsley for providing access to the PSMN computer cluster and D. Sebastiani and M. Hansen for fruitful discussions.

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