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Issue 10, 2018
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Site-specific binding of a water molecule to the sulfa drugs sulfamethoxazole and sulfisoxazole: a laser-desorption isomer-specific UV and IR study

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Abstract

To determine the preferred water molecule binding sites of the polybasic sulfa drugs sulfamethoxazole (SMX) and sulfisoxazole (SIX), we have studied their monomers and monohydrated complexes through laser-desorption conformer-specific UV and IR spectroscopy. Both the SMX and SIX monomer adopt a single conformer in the molecular beam. On the basis of their conformer-specific IR spectra in the NH stretch region, these conformers were assigned to the SMX and SIX global minimum structures, both exhibiting a staggered sulfonamide group and an intramolecular C–H⋯O[double bond, length as m-dash]S hydrogen bond. The SMX–H2O and SIX–H2O complexes each adopt a single isomer in the molecular beam. Their isomeric structures were determined based on their isomer-specific IR spectra in the NH/OH stretch region. Quantum Theory of Atoms in Molecules analysis of the calculated electron densities revealed that in the SMX–H2O complex the water molecule donates an O–H⋯N hydrogen bond to the heterocycle nitrogen atom and accepts an N–H⋯O hydrogen bond from the sulfonamide NH group. In the SIX–H2O complex, however, the water molecule does not bind to the heterocycle but instead donates an O–H⋯O[double bond, length as m-dash]S hydrogen bond to the sulfonamide group and accepts an N–H⋯O hydrogen bond from the sulfonamide NH group. Both water complexes are additionally stabilized by a Cph–H⋯OH2 hydrogen bond. Interacting Quantum Atoms analysis suggests that all intermolecular hydrogen bonds are dominated by the short-range exchange–correlation contribution.

Graphical abstract: Site-specific binding of a water molecule to the sulfa drugs sulfamethoxazole and sulfisoxazole: a laser-desorption isomer-specific UV and IR study

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Publication details

The article was received on 22 Dec 2017, accepted on 12 Feb 2018 and first published on 13 Feb 2018


Article type: Paper
DOI: 10.1039/C7CP08579F
Citation: Phys. Chem. Chem. Phys., 2018,20, 6891-6904
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    Site-specific binding of a water molecule to the sulfa drugs sulfamethoxazole and sulfisoxazole: a laser-desorption isomer-specific UV and IR study

    T. Uhlemann, S. Seidel and C. W. Müller, Phys. Chem. Chem. Phys., 2018, 20, 6891
    DOI: 10.1039/C7CP08579F

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