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Exchange Reaction Mechanism of <TEX>$Pb(II)-N_2O_m$</TEX> Macrocyclic Complexes by <TEX>$^{207}Pb-NMR$</TEX> Spectroscopy
Exchange Reaction Mechanism of $Pb(II)-N_2O_m$ Macrocyclic Complexes by $^{207}Pb-NMR$ Spectroscopy
Journal of the Korean Chemical Society. 1994. Jan, 38(1): 41-49
  • Published : January 00, 1994
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Kim, Jeong
Yun, Chang Ju
Yu, Han Jun
Kim, Geon
Kim, Si Jung

Abstract
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 : $1011-dibenzo-59-dioxacyclohexa-decane(NtnOtnH_4)$, 1,15-diaza-3,4 : $1213-dibenzo-5811-trioxacycloheptadecane(NenOdienH_4)$, and 1,15-diaza-3,4 : $1213-dibenzo-5811-trioxacyclooctadecane(NtnOdienH_4)$, were studied by $^{207}Pb-NMR$ spectroscopy in N,N'-dimethylformamide(DMF) solutions. The associative-dissociative mechanism dominated in $NtnOtnH_4-Pb(II)$ and $NtnOdienH_4-Pb(II)$ system. For $NenOdienH_4-Pb(II)$ system, the bimolecular exchange mechanism prevailed below $-5^{\circ}C$, and both bimolecular exchange and associative-dissociative mechanism dominated above $+5^{\circ}C.$ The order of activation energies for dissociation was $NtnOdienH_4\;<\;NtnOtnH_4\;<\;NenOdienH_4$ which was reverse to the order of stabilities.