Syntheses, crystal structures and antioxidant study of Zn(II) complexes with morin-5′-sulfonic acid (MSA)

• The synthesis of the sodium salt of morin-5′-sulfonic acid (NaMSA) was described.
• The NaMSA salt is a source of anionic morin-5'-sulfonic ligand (MSA).
• The coordination ability of MSA ligand towards the zinc cations was investigated.
• Zn–MSA complex formation of a 1D chain or 3D structural coordination polymer
• The antioxidant activity of the NaMSA and Zn–MSA complexes is higher than morin.

The study of modified synthetic procedure of water soluble morin-5′-sulfonic acid sodium salt (NaMSA) involving less aggressive chemicals and carried out at mild conditions was described. The NaMSA salt is a convenient source of anionic morin-5'-sulfonic ligand (MSA) in ion exchange reactions. The coordination ability of MSA ligand towards the zinc cations was investigated in aqueous solution and in solid state. Novel zinc complexes of morin-5'-sulfonate were obtained by a reaction of Zn(NO3)2 with morin-5'-sulfonate in water. Resulting compounds were characterized by single-crystal X-ray diffraction analysis, as well as spectral and thermal methods. The coordination interaction, hydrogen bond and π–π stacking lead to the formation of a 1D chain or 3D coordination polymers. The antioxidant activity of the Zn(II)–MSA complexes was evaluated by means of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method. In this work, we have shown that the studied compounds are more effective free radical scavengers than the natural flavonoids like plain morin.

The ability of morin-5′-sulfonic anion (MSA) to bind zinc metal has been shown. The first crystal structures in which sulfonated flavonoid based ligand coordinates to the metal are presented. The water soluble complexes are characterized by crystallographic and spectroscopic methods, and show higher antioxidant activity as compared to the morin.Figure optionsDownload as PowerPoint slide