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Exchange reaction mechanisms of the Pb(Ⅱ) ion for the complexes between Pb(Ⅱ) ion and nitrogen oxygen donor macrocyclic ligands, such as 1,13-diaza-3,4 : 10,11-dibenzo-5,9-dioxacyclohexa-decane(NtnOtnH4), 1,15-diaza-3,4 : 12,13-dibenzo-5,8,11-trioxacycloheptadecane(NenOdienH4) and 1,15-diaza-3,4 : 12,13-dibenzo-5,8,11-trioxacyclooctadecane(NtnOdienH4) were studied by 207Pb-NMR spectroscopy in N,N'-dimethylformamide(DMF) solutions. The associative-dissociative mechanism dominated in NtnOtnH4-Pb(Ⅱ) and NtnOdienH4-Pb(Ⅱ) system. For NenOdienH4-Pb(Ⅱ) system, the bimolecular exchange mechanism prevailed below -5℃, and both bimolecular exchange and associative-dissociative mechanism dominated above +5℃. The order of activation energies for dissociation was NtnOdienH4 < NtnOtnH4 < NenOdienH4 which was reverse to the order of stabilities.
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