title: 4-(Dimethyl-amino)pyridinium 2-(4-hydroxy-phenyl-diazen-yl)benzoate.
abstract: In the title molecular salt, C(7)H(11)N(2) (+)·C(13)H(9)N(2)O(3) (-), the dihedral angle between the benzene rings in the anion is 35.14 (8)°. In the crystal, centrosymmetrically related anions associate via hydrox-yl-carboxyl-ate O-H⋯O hydrogen bonds, resulting in a 24-membered {⋯OC(3)N(2)C(4)OH}(2) synthon. The cations are associated with this dimeric unit via pyridinium-carboxyl-ate N-H⋯O hydrogen bonds. Weak C-H⋯O links further consolidate the packing, generating layers.
authors.forename: Hadi D
authors.initials: HD
authors.lastname: Arman
authors.forename: Tyler
authors.initials: T
authors.lastname: Miller
authors.forename: Edward R T
authors.initials: ER
authors.lastname: Tiekink