Polymorphism and structural diversities of LiClO4 - β-alanine ionic co-crystals
Three novel ionic co-crystals (ICCs) built of lithium perchlorate and β-alanine (LiClO4·βAla, LiClO4·2βAla-I, LiClO4·2βAla-II) were obtained and structurally characterized. Crystals with a twofold excess of amino acid, LiClO4·2βAla-I, were found to undergo a solvent-mediated phase transition, recrystallizing as thermodynamically stable polymorph LiClO4·2βAla-II. The transition was characterized by a series of PXRD measurements, observations performed under the microscope in polarized light as well as DSC experiments. Both polymorphs were found to exhibit virtually the same square-grid topology of lithium-alanine coordination sheets, yet they differ in symmetry and geometrical parameters of the networks. In LiClO4·βAla crystal structure chain-like coordination polymers are formed. Response to the temperature change was determined in all three structures by performing a series of X-ray diffraction measurements in 100 – 300 K range. Differences were elucidated with the help of thermal tensor, which allowed to identify structural motives the most sensitive to the temperature change.