title: Structural and Computational Study of 4 New Solvatomorphs of Betulin: A Combined X-Ray, Hirshfeld Surface, and Thermal Analysis.
abstract: Four new solvatomorphs of betulin were reported and characterized by X-ray diffractometry as well as thermal and vibrational spectroscopic analyses. Single-crystal X-ray diffraction was used to analyze the X-ray structures of the compounds and confirmed the stoichiometric ratio between the host and guest molecules from thermal data. Results indicated that solvatomorphism occurred in several betulin solvates. Changes in intermolecular arrangements, stoichiometry, and hydrogen-bonding interactions of solvatomorphs were due to solvent incorporation to solvates. Hirshfeld surface analyses, especially dnormsurface and fingerprint plots, were used to determine intermolecular interactions in the crystal network. Solvent molecules played an important role in the construction of a 3D architecture. The stabilities of these solvates were evaluated by thermal analyses. Nonisothermal kinetic analysis was used to explain the kinetics of solid-solid phase transition (desolvation) of betulin solvates. The apparent activation energies were evaluated using Kissinger and Ozawa methods. Moreover, phase transitions were visually investigated by hot-stage microscopic analysis.
authors.affiliation: Beijing City Key Laboratory of Polymorphic Drugs, Center of Pharmaceutical Polymorphs, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
authors.forename: Dezhi
authors.initials: D
authors.lastname: Yang
authors.affiliation: Beijing City Key Laboratory of Polymorphic Drugs, Center of Pharmaceutical Polymorphs, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
authors.forename: Ningbo
authors.initials: N
authors.lastname: Gong
authors.affiliation: Beijing City Key Laboratory of Polymorphic Drugs, Center of Pharmaceutical Polymorphs, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Beijing City Key Laboratory of Polymorphic Drugs, Center of Pharmaceutical Polymorphs, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China. Electronic address: luy@imm.ac.cn.
authors.forename: Yang
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Beijing City Key Laboratory of Drug Target and Screening Research, National Center for Pharmaceutical Screening, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
authors.forename: Guanhua
authors.initials: G
authors.lastname: Du
mesh_terms: D003460:Crystallization / Q000379:methods; D018360:Crystallography, X-Ray / Q000379:methods; D004055:Differential Thermal Analysis / Q000379:methods*; D008956:Models, Chemical; D012997:Solvents / Q000032:analysis* / Q000737:chemistry*; D013818:Thermogravimetry / Q000379:methods; D014961:X-Ray Diffraction / Q000379:methods*
chemical_list: D012997:Solvents
keywords: betulin; crystal structure; solvatomorph; thermal analysis; vibrational spectroscopy