Hydrogen Bonding and Aromatic π–π Stacking in the Crystal Structures of Water-Soluble Daidzein Derivatives

Abstract

Water-soluble daidzein derivatives, [Ni(H2O)6](C16H11O4SO3)2⋅10H2O and [Zn(H2O)6] (C16H11O4SO3)2⋅10H2O (C16H11O4SO3, 7-methoxy-4′-hydroxylisoflavone-3′-sulfonate) were synthesized and their crystal structures were determined by X-ray diffraction analysis. The crystals of them all belong to triclinic crystal system, space group P\(\bar{1}\). The results show that the two derivatives consist of metal cation [Ni(H2O)6]2+ and [Zn(H2O)6]2+, anion C16H11O4SO3− and H2O. Ni2+ and Zn2+ are the centers of the two compounds, respectively. A hydrophilic region is built by a variety of hydrogen bonds among [Ni(H2O)6]2+ or [Zn(H2O)6]2+, C16H11O4SO3− and the lattice water molecules. Aromatic π–π stacking interactions assemble the isoflavone skeletons into a column and the columns form a hydrophobic region of daidzein derivatives. The sulfo-groups bridge the hydrophilic and hydrophobic region as well as the inorganic and organic components.