A trinuclear oxo-chromium(III) complex containing the natural flavonoid primuletin: synthesis, characterization, and antiradical properties.

A new trinuclear oxo-centered chromium(III) complex with formula [Cr3O(CH3CO2)6(L)(H2O)2] (L = 5-hydroxyflavone, known as primuletin) was synthetized and characterized by ESI mass spectrometry, thermogravimetry, and 1H-NMR, UV-Vis, and FTIR spectroscopies. In agreement with the experimental results, DFT calculations indicated that the flavonoid ligand is coordinated to one of the three Cr(III) centers in an O,O-bidentate mode through the 5-hydroxy/4-keto groups. In a comparative study involving the uncoordinated primuletin and its corresponding complex, systematic reactions with the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) showed that antiradical activity increases upon complexation.