title: Three polymorphic forms of the co-crystal 4,4'-bipyridine/pimelic acid and their structural, thermal, and spectroscopic characterization.
abstract: Three crystal forms of the co-crystal 4,4'-bipy/pimelic acid (bipy: bipyridine), [NH(4)C(5)-C(5)H(4)N][HOOC(CH(2))(5)COOH], have been prepared and their relationship investigated by single-crystal X-ray diffraction, variable-temperature X-ray powder diffraction, differential scanning calorimetry and solid-state NMR spectroscopy. Both X-ray and NMR spectroscopic results indicate that no proton transfer takes place, that is, the three crystal forms are true co-crystals of neutral molecules. Forms I and II both convert into Form III at high temperature, Forms II and III being the thermodynamically stable forms at room and high temperature, respectively.
authors.affiliation: Dipartimento di Chimica "G. Ciamician", Università degli studi di Bologna, Via Selmi 2, 40126 Bologna, Italy.
authors.forename: Dario
authors.initials: D
authors.lastname: Braga
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Palladino
authors.forename: Marco
authors.initials: M
authors.lastname: Polito
authors.forename: Katia
authors.initials: K
authors.lastname: Rubini
authors.forename: Fabrizia
authors.initials: F
authors.lastname: Grepioni
authors.forename: Michele R
authors.initials: MR
authors.lastname: Chierotti
authors.forename: Roberto
authors.initials: R
authors.lastname: Gobetto