[摘要]：Three crystal forms of the co-crystal 4,4'-bipy/pimelic acid (bipy:bipyridine), [NH4C5-C5H4N]譡HOOC(CH2)5COOH], have been prepd. and their relationship investigated by single-crystal x-ray diffraction, variable-temp. 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, i.e., the three crystal forms are true co-crystals of neutral mols. Forms I and II both convert into Form III at high temp., Forms II and III being the thermodynamically stable forms at room and high temp., resp.
