Ion-dipole interactions of macrocyclic ethers using C-13 dipole-dipole relaxation time measurements .11. The complexation of 1,4,7,10,13,16-hexaoxa-2,6-dioxocyclooctadecane with Ca2+ in CD3OH


Erk C.

JOURNAL OF INCLUSION PHENOMENA AND MOLECULAR RECOGNITION IN CHEMISTRY, vol.26, pp.61-66, 1996 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 26
  • Publication Date: 1996
  • Doi Number: 10.1007/bf01029928
  • Title of Journal : JOURNAL OF INCLUSION PHENOMENA AND MOLECULAR RECOGNITION IN CHEMISTRY
  • Page Numbers: pp.61-66

Abstract

The association constants, K-a, of Ca2+ complexes with the nonequivalent binding site macrocycle, 1, 4, 7, 10, 13, 16-hexaoxa-2, 6-dioxocyclooctadecane, were determined in CD3OH solution using C-13 dipole-dipole relaxation time, T-1(DD), studies. The measurements of T-1(DD) of the macrocyclic backbone for different stoichiometries (n : m) of complex formation were conducted under extreme narrowing experimental NMR conditions. The general equilibria given with 1/K-a[L(0)](n+m-l) = (1 - nP')(n) (1 - mP')(m)/P' was used for identical cation and macrocyclic ether-ester concentrations in CD3OH and the association constants found were comparatively small depending on the cyclic ether-ester segments. The log K-a values varied from 1.09 to 0.231 for 1 : 1 and from 2.43 to 3.61 for 1 : 2 and from 2.29 to 4.24 for 2 : 1 ligand to cation complex stoichiometries.