Polymorphism and structural diversities of LiClO4–β-alanine ionic co-crystals

• Published in: CrystEngComm 2020-07, Vol.22 (26), p.4427-4437
• Main Authors: Marek, Paulina H, Cichowicz, Grzegorz, Osowicka, Dorota M, Madura, Izabela D, Dobrzycki, Łukasz, Cyrański, Michał K, Ciesielski, Arkadiusz
• Format: Article
• Language: English
• Subjects: Alanine; Coordination polymers; Crystal structure; Crystallography; Crystals; Diffraction patterns; Lithium; Mathematical analysis; Parameters; Phase transitions; Polarized light; Polymorphism; Recrystallization; Stoichiometry; Tensors; Thermal expansion; Topology; Unit cell
• ISSN: 1466-8033
• DOI: 10.1039/d0ce00592d

Three novel ionic co-crystals (ICCs) built from 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 the thermodynamically stable polymorph LiClO4·2βAla-II. The transition was characterized by a series of PXRD measurements, observations performed under a microscope with polarized light and 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 the LiClO4·βAla crystal structure, chain-like coordination polymers are formed. Responses to temperature change were determined for all three structures by performing a series of X-ray diffraction measurements in the 100–300 K range. Differences were elucidated with the help of a thermal tensor, which allowed us to identify the structural motifs most sensitive to temperature change.