On the relationships between molecular conformations and intermolecular contacts toward crystal self-assembly of mono-, di-, tri-, and tetra-oxygenated xanthone derivatives

• Published in: Structural chemistry Vol. 21; no. 3; pp. 555 - 563
• Main Authors: Corrêa, Rodrigo S., dos Santos, Marcelo H., Nagem, Tanus J., Ellena, Javier
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01-06-2010
• Subjects: Chemistry; Chemistry and Materials Science; Computer Applications in Chemistry; Original Research; Physical Chemistry; Theoretical and Computational Chemistry; π–π interactions; Molecular conformation; Hirshfeld surfaces; Hydrogen bonds; Oxygenated xanthones
• ISSN: 1040-0400; 1572-9001
• DOI: 10.1007/s11224-010-9582-1

Oxygenated xanthones have been extensively investigated over the years, but there are few reports concerning their crystal structure. Our chemical investigations of Brazilian plants resulted in the isolation of four natural products named 1-hydroxyxanthone (I), 1-hydroxy-7-methoxyxanthone (II), 1,5-dihydroxy-3-methoxyxanthone (III), and 1,7-dihydroxy-3,8-dimethoxyxanthone (IV). The structures of these compounds were established on the basis of single crystal X-ray diffraction. The xanthone nucleus conformation is essentially planar with the substituents adopting the orientations less sterically hindered. In addition, classical intermolecular hydrogen bonds (O–H···O) present in III and IV give rise to infinite ribbons. However, the xanthone I does not present any intermolecular hydrogen bonds, meanwhile the xanthone II presents only a non-classical one (C–H···O). The crystal packing of all xanthone structures is also stabilized by π–π interactions. The fingerprint plots, derived from the Hirshfeld surfaces, exhibited significant features of each crystal structures.