Abstract: The title macrocyclic complex [Ho(H2L)(NO3)2](NO3) (H2L denotes the macrocyclic ligand, Fig. 1) has been synthesized and characterized by elemental analysis, infrared spectra, and electrospray mass spectra. Its crystal and molecular structures were determined by X-ray diffraction methods. The crystal crystallizes in the hexagonal system, space group P3(1)21 with a=1.47213(7) nm， c=2.8998(3) nm，α=90°，γ=120°，V=5.4424(7) nm 3，Z=6，R＝0.0331, wR＝0.0928。 The central holmium ion was located in one of the compartments of the macrocyclic ligand and was coordinated with two oxygen and three nitrogen atoms of the macrocycle. Two nitrates were chelated in the opposite positions of the macrocycle, and the third one is ionic. So the central ion presented a distorted tricapped trigonal prismatic coordination geometry. The preliminary studies of cleavage of double stranded DNA was demonstrated by electrophoresis gel.

Key words: macrocyclic ligand, holmium nitrate complex；synthesis；crystal structure；DNA cleavage