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 fourcoordinated 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.

Key words: dichlorosalicylaldehyde, copper(II) complex, crystal, spectral characteristics