Tryptanthrin(Try)is a natural alkaloid.The halogenated derivative,8-bromo-tryptanthrin and its Fe(Ⅱ)complex [Fe(8-Br-Try)4](1)were synthesized and characterized.Single crystal X-ray diffraction analysis indicated that 1 showed a distorted octahedral geometry with Fe(Ⅱ)ion in a hexacoordinated environment and two of 8-Br-Try dimers as tridentate chelating ligands.The complex was found to display a strong preference for G-quadruplex with a binding constant of 8.70×106 dm~3·mol~(-1) by UV-Vis titration and flu...