The macrocyclic ligand(L) and its dinuclear copper(Ⅱ) and zinc(Ⅱ) complexes have been synthesized. The crystal structure of [Cu 2L(Him) 2](ClO 4) 4·2H 2O has been determined by single crystal X ray diffraction. It crystallizes in a monoclinic system, the space group P2 1/c , a =0.951 2(2) nm, b =2.010 4(4) nm, c =1.202 5(2) nm, β =98.89(3)°, V =2.271 9(8) nm 3, Z=2, D c=1.599 Mg/m 3 , F (000) = 876 , R =0.059 1, wR =0.173 3, GOF(F)=1.009. The copper(Ⅱ) atom is five coordinated with four nitrogen atoms of the macrocyclic ligand and one nitrogen atom of imidazole. The stepwise stability constants of the 1∶1 and 2∶1 molar ratios of Cu to L and Zn to L complexes were determined by potentiometric titration in KCl supporting electrolyte(0.100 mol/L) at 25 ℃. The results indicated that zinc(Ⅱ) ion can form hydroxide bridged dinuclear complex [Zn 2(OH)L] 3+ , while the copper(Ⅱ) ion can only form dinuclear complex 3+ with macrocyclic ligand.
