title: A red zwitterionic co-crystal of acetaminophen and 2,4-pyridinedicarboxylic acid.
abstract: We report on a co-crystal of acetaminophen (APAP) and 2,4-pyridinedicarboxylic acid (PDA). The co-crystal was discovered by screening using the solution-mediated phase transformation (SMPT) technique. Despite the bulk solids of each component being white in color, the new co-crystal phase exhibited a red color. The new phase was analyzed using single-crystal X-ray diffraction and identified as (APAP).(PDA).(1). Structural analysis revealed PDA to exist in a hitherto unreported zwitterionic form in the co-crystal. A structural analysis of pure PDA revealed the presence of the zwitterion form in (PDA).(H(2)O) (2), as well. The components of 1 self-assemble as a three-dimensional (3D) hydrogen-bonded network with a pronounced 2D structure. The origin of the red color was investigated using density functional theory calculations, which demonstrate a decreasing pi-pi(*) separation involving the components of the solid.
authors.affiliation: Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, USA.
authors.forename: John R G
authors.initials: JR
authors.lastname: Sander
authors.forename: Dejan-Kresimir
authors.initials: DK
authors.lastname: Bucar
authors.forename: Rodger F
authors.initials: RF
authors.lastname: Henry
authors.forename: Jonas
authors.initials: J
authors.lastname: Baltrusaitis
authors.forename: Geoff G Z
authors.initials: GG
authors.lastname: Zhang
authors.forename: Leonard R
authors.initials: LR
authors.lastname: MacGillivray
mesh_terms: D000082:Acetaminophen / Q000737:chemistry*; D018712:Analgesics, Non-Narcotic / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D011725:Pyridines / Q000737:chemistry*
chemical_list: D018712:Analgesics, Non-Narcotic; D011725:Pyridines; D000082:Acetaminophen; C055293:2,4-pyridinedicarboxylic acid