Abstract: A Schiff base ligand,N,N'-bis(3,5-dichlorosalicylaldehyde)-o-phenylenediamine,and its copper complex was synthesized.The compound was characterized by elemental analysis,FTIR,TG-DTG,single crystal X-ray diffraction,UV-Vis absorption spectroscopy,and fluorescence excitation and emission spectra.The high thermal decomposition temperature of 384℃ for the complex showed that it had high thermal stability.In its infrared spectrum,a strong band was observed at about 1616 cm^-1. This band was due to the conjugated C=N stretching vibration,and was shifted to higher frequency compared with the free ligand of 3,5-dichlorosalicylaldehyde and o-phenylenediamine.The new band at 530 cm^-1 was assigned to Cu-O stretching vibration.The crystal of the copper(Ⅱ) complex belongs to monoclinic system with space group,P2(1)/n,a=0.81316(8) nm,b=1.53101(18) nm,c=1.87819(19) nm,β=92.4530(10)°,Z=4, the final R₁=0.058, and ωR₂=0.148.The central copper ion of the complex coordinated with the two O and two N of the Schiff base to form a five-membered ring and two six-membered rings,which constituted a fourcoordinated planar conformation.The complex's UV absorption bands were at about 268,310 and 435 nm,where the absorption band at about 435 nm can be assigned to the intrinsic absorption of C=N.Its fluorescence excitation is in the range of 360~480 nm,and its DMF solution emitted intensive blue-green fluorescence at the peak wavelength of 507 nm.Its optical gap was about 2.59 eV,which was determined by the intrinsic absorption band edge of the complex in DMF solution.