Synthesis and properties of zirconium(IV) and molybdate(II) morin complexes

Morin, an excellent chelating agent, has been used to form complex with a metal cation (Zr-4(+)) and a metal oxyanion (MoO42-), isolating highly colored [Zr(C15H9O7)(2)(NO3)(2)]center dot 2H(2)O (1) and [MoO3(C15H9O7)(2)]center dot 3H(2)O (2). The structures were elucidated using different techniques (i.e., electrical conductance, elemental, and thermal analyses) as well as a series of spectroscopic techniques (i.e., UV-Vis, IR, and H-1 NMR). The stoichiometry of the complexes is 1:2, confirmed by the molar ratio method. Zr-4(+) is useful for structural diagnosis of different flavonoids. The preferred site of complex formation of morin is the 3-hydroxy-4-keto system. Complex 2 is more stable than 1. Fluorescence and cyclic voltammetry were studied. Antioxidative study affirmed that both 1 and 2 are efficient antioxidants relative to morin.