Conformational Polymorphism and Isomorphism of Molecular Rotors with Fluoroaromatic Rotators and Mestranol Stators

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• 作者：Braulio Rodr铆guez-Molina ; Ma. Eugenia Ochoa ; Margarita Romero ; Saeed I. Khan ; Norberto Farf谩n ; Rosa Santillan ; Miguel A. Garcia-Garibay
• 刊名：Crystal Growth & Design
• 出版年：2013
• 出版时间：November 6, 2013
• 年：2013
• 卷：13
• 期：11
• 页码：5107-5115
• 全文大小：414K
• 年卷期：v.13,no.11(November 6, 2013)
• ISSN：1528-7505

文摘

We report the synthesis and characterization of four molecular rotors 2, 3, 4, and 5 containing 2-fluoro-, 2,3-difluoro-, 2,5-difluoro-, and 2,3,5,6-tetrafluoro-substituted 1,4-phenylene rotators, respectively, that are axially linked through the triple bonds of rigid mestranol (3-methoxy-17伪-ethynylestradiol) stators. Crystallization experiments using solvent mixtures of hexanes鈥揺thyl acetate and acetonitrile鈥揹ichloromethane gave rise to polymorphic, pseudopolymorphic, and isomorphic crystals. Whereas two solids were obtained for compound 2, four were indentified in the cases of compounds 3 and 4, and three for compound 5. The 13 solid forms were characterized by single-crystal and powder X-ray diffraction, infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Two sets of isomorphous structures were obtained for solvated and solvent-free structures of compounds 3鈥?b>5. While polymorphic behavior of these compounds arises from their conformational freedom in solution, their isomorphism arises from the closely isosteric relation that exists between hydrogen and fluorine atoms.