Control of crystal structure using temperature and time.

Three novel crystal structures were obtained from iron(III) acetylacetonate and 2,6-pyridinedicarboxylic acid. The structures elucidated were found to be dependent on the temperature and length of time allowed for the reaction. The product of the reaction between iron(III) acetylacetonate and 2,6-pyridinedicarboxylic acid in acetonitrile at room temperature is [FeC12H12NO7]·CH3CN, (I). When the reaction temperature was increased to 60°C, FeC12H10NO6, (II), was isolated after 2 h and [FeC12H10NO6]4, (III), was isolated after 24 h. (I) is a discrete complex, whereas (II) and (III) form tetramers.