Abstract: The homogeneous solution of poor soluble aza-bridged bis-phenanthroline macrocycle H₂HAPP was obtained via the deprotonation of its trifluoroacetate in a mixed solvent‚and the high resolved UV-Vis spectra of H₂HAPP were recorded in solution．Protonation reaction of H₂HAPP in CH₂Cl₂／CH₃OH solvent （the volume ratio of CH₂Cl₂ to CH₃OH is 1∶1） was studied via pH titration．The results indicate that the two outer nitrogen atoms of H 2 HAPP are protonized independently with different pH values．Spectroscopic titration result shows that the coordination reaction between this macrocyclic ligand and metal ions（Co^2＋‚Cu^2＋ and Zn_2＋）goes smoothly in such a homogeneous system．

Key words: aza-bridged bis-phenanthroline macrocycle, metal ion, homogeneous coordination reaction