Title of article :
Crystal structure of a 2:1 piroxicam–gentisic acid co-crystal featuring neutral and zwitterionic piroxicam molecules
Author/Authors :
Horstman, Elizabeth M. University of Illinois - Department of Chemical and Biomolecular Engineering, USA , Bertke, Jeffery A. University of Illinois - School of Chemical Sciences, USA , Woods, Toby J. University of Illinois - School of Chemical Sciences, USA , Kenis, Paul J. A. University of Illinois - Department of Chemical and Biomolecular Engineering, USA
Abstract :
A new 2:1 co-crystal of piroxicam and gentisic acid [systematic name: 4-hydroxy-1,1-dioxo-N-(pyridin-2-yl)-2H-1λ6,2-benzothiazine-3-carboxamide–2-(4-oxido-1,1-dioxo-2H-1λ6,2-benzothiazine-3-amido)pyridin-1-ium–2,5-dihydroxybenzoic acid, 2C15H13N3O4S·C7H6O4] has been synthesized using a microfluidic platform and initially identified using Raman spectroscopy. In the co-crystal, one piroxicam molecule is in its neutral form and an intramolecular O—H⋯O hydrogen bond is observed. The other piroxicam molecule is zwitterionic (proton transfer from the OH group to the pyridine N atom) and two intramolecular N—H⋯O hydrogen bonds occur. The gentisic acid molecule shows whole-molecule disorder over two sets of sites in a 0.809 (2):0.191 (2) ratio. In the crystal, extensive hydrogen bonding between the components forms layers propagating in the ab plane.
Keywords :
crystal structure , hydrogen bonding , piroxicam
Journal title :
Acta Crystallographica Section E: Crystallographic Communications