title: Crystal structure of a 2:1 piroxicam-gentisic acid co-crystal featuring neutral and zwitterionic piroxicam mol-ecules.
abstract: A new 2:1 co-crystal of piroxicam and gentisic acid [systematic name: 4-hy-droxy-1,1-dioxo-N-(pyridin-2-yl)-2H-1λ6,2-benzo-thia-zine-3-carboxamide-2-(4-oxido-1,1-dioxo-2H-1λ6,2-benzo-thia-zine-3-amido)-pyridin-1-ium-2,5-di-hydroxy-benzoic acid, 2C15H13N3O4S·C7H6O4] has been synthesized using a microfluidic platform and initially identified using Raman spectroscopy. In the co-crystal, one piroxicam mol-ecule is in its neutral form and an intra-molecular O-H⋯O hydrogen bond is observed. The other piroxicam mol-ecule is zwitterionic (proton transfer from the OH group to the pyridine N atom) and two intra-molecular N-H⋯O hydrogen bonds occur. The gentisic acid mol-ecule shows whole-mol-ecule 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 theabplane.
authors.affiliation: University of Illinois, Department of Chemical and Biomolecular Engineering, 600 S. Mathews Ave, Urbana, IL 61801, USA.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Horstman
authors.affiliation: University of Illinois, School of Chemical Sciences, Box 59-1, 505 South Mathews Avenue, Urbana, Illinois 61801, USA.
authors.forename: Jeffery A
authors.initials: JA
authors.lastname: Bertke
authors.affiliation: University of Illinois, School of Chemical Sciences, Box 59-1, 505 South Mathews Avenue, Urbana, Illinois 61801, USA.
authors.forename: Toby J
authors.initials: TJ
authors.lastname: Woods
authors.affiliation: University of Illinois, Department of Chemical and Biomolecular Engineering, 600 S. Mathews Ave, Urbana, IL 61801, USA.
authors.forename: Paul J A
authors.initials: PJ
authors.lastname: Kenis
keywords: crystal structure; hydrogen bonding; piroxicam