粉末X線結晶構造解析で解明する5-メチル-2-ピリドン共結晶の光反応性と転移現象

抄録

Crystal A which is methanol solvate co-crystal of 5-methyl-2-pyridone (5MP) and trimesic acid (TMA) was found to transform to crystal B by grinding at atmosphere and both crystal A and B are found to transform to crystal C by heating. Interestingly, although crystal A and crystal B are not photo-reactive phase of pyridone, crystal C is photo-reactive and gave a pure [4 + 4] cis-syn pyridone dimer. In order to reveal the transformation mechanisms and the photo-reactivity, crystal structures of crystal B and crystal C were analyzed from X-ray powder diffraction data. The structural analyses revealed that crystal B is a hydrate co-crystal and crystal C is an unsolvated co-crystal. From the crystal structures, the photo-reactivity of these phases can be clearly explained by the reaction cavities of pyridone molecules in their crystals. These structural analyses also revealed that the transformation from crystal A to B is a solvent exchange process and crystal A or B to C is a desolvation process. Further, vapor induced transformations have been investigated for crystal A, B and C to establish the transformation mechanisms from the crystal structures point of view.