Synthesis, Crystal Structure, and Biological Activity of Two Complexes based on 5-hydroxy-4′-methoxyisoflavone-3′-sulfonate

Abstract

Two metal complexes [Mn(H₂O)₆(C₁₆H₁₁O₇S)₂] · 2H₂O (I) and Al(H₂O)₃(C₁₆H₁₁O₇S) · 2H₂O (II) were synthesized by reaction of the sodium 5-hydroxy-4′-methoxyisoflavone-3′-sulfonate (C₁₆H₁₁O₇SNa) with MnSO₄ · 4H₂O or Al(NO₃)₂ · 6H₂O, respectively. Complex I and II were characterized by the single crystal X-ray diffraction (CIF files CCDC nos. 1563980 (I), 1563981 (II)), IR spectroscopy, thermogravimetric and elemental analysis. For complex I, the coordination number of Mn(II) is 6 and the coordinated atoms are all oxygen atoms from six H₂O molecules. For complex II, the coordination number of Al(III) is 4, and coordinated atoms come not only from three water molecules but also the sulfo-group. Furthermore, I and II have hydrogen bonding and π···π stacking supramolecular interactions. Hydrogen bonding forms a hydrophilic region, π···π stacking forms a hydrophobic region. The sulfo-group is a vital bridge between the hydrophilic region and the hydrophobic region, which improves the water-soluble ability and prompts the versatile assembly of pallidiflorin with metal ion. In addition, the preliminary biological test showed that I, II had antimicrobial activities.