Unique Complexation Behavior of Alkali Metal Ions and 2-Pyrone-4,6-Dicarboxylic Acid (PDC) Obtained from a Metabolic Intermediate of Lignin

The complexation behavior between 2-pyrone-4,6-dicarboxylic acid (PDC) and alkali metal ions was systematically estimated. The PDC complexes of alkali metal ions exhibit unique crystal structures due to the diverse coordination numbers of the metal ion. The crystal structure of the complex between PDC and cesium (Cs) ion suggests that the metal ion binary crosslinking and much coordination numbers of the Cs induce the preferential complex formation via sedimentation of the PDC-Cs complex. The minor electronegativity difference between the Cs and other alkali metals might be the determining factor in the structure of the complex the ion forms with PDC.