The complexes of thiaxanthon-2-yl-oxyacetate with rare earths were synthesized. The structure of such complexes was characterized by elemental analysis, IR, ¹H NMR, UV, DTA-TG and ¹³C NMR spectrum. The results suggested that their composition should be M∶L＝1∶3 (M＝RE^3＋, L＝thiaxanthon-2-yl-oxyacetate), the metal should be coordinated to not only carboxylic oxygen but also ether oxygen, and the complex should be non-electrolyte with coordinating water molecule. The interaction between the Eu(III) complex of thiaxanthon-2-yl-oxyacetate and plasmid DNA was studied by agarose gel electrophoresis. The data showed that the cleavage of plasmid DNA might depend on the concentration of the complex. The higher concentration of the complex caused the larger decrease of DNA super helix. Under the same concentration, the complex and thiaxanthon-2-yl-oxyacetate had obvious plasmid DNA cleavage ability but Eu(III) had very little. The complex had stronger plasmid DNA cleavage ability than ligand. The results suggested that rare earth ions had good synergism with ligand in cleavage of plasmid DNA.

Key words: synthesis, characterization, thiaxanthon-2-yl-oxyacetate, rare earth complex, cleavage of DNA