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The protonation and the metal ion complexation of 15 to 18 membered diaza crown ether such as 1,12-diaza-3, 4 : 9, 10-dibenzo-5, 8-dioxacyclopentadecane(NtnOenH4), 1,13-diaza-3,4 : 10,11-dibenzo-hydroxy-5,9-dioxacyclohexadecane(NtnOtnH4), 1,13-diaza-3,4 : 10,11-dibenzo-15-hydroxy-5,9-dioxacyclohexadecane(Ntn(OH)OtnH4), 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 studlied by potentiometry and NMR spectroscopy. The protonation constants were used to predict basicity of crown ethers. The sequence of the basicity was NenOdienH4 < Ntn(OH)OtnH4 < NtnOenH4 < NtnOtnH4 < NtnOdienH4. Changes on the basicity were explained in terms of the effects of substituents and the degree of twistness of the macrocyclic ring. The sequence of the complex stabilities were Co(Ⅱ) < Ni(Ⅱ) < Cu(Ⅱ) < Zn(Ⅱ) for the transition metal complexes and Cd(Ⅱ) < pb(Ⅱ) < Hg(Ⅱ) for the post-transition metal complexes. These changes on the stabilities were dependent on the basicity of the ligand and cavity size of the ring. For the heavy post-transiton metal complexes and Zn(Ⅱ) complex, the former factor was predominent and for the other transition metal complexes, the latter was affected on the stabilities. 1H and 13C-NMR studies for heavy post-transition metal complexes indicated that the nitrogen atom has greater affinity on metal ions than oxygen atom and the planarity of the rings was losed by the complexation with metal ions.
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