Solution structures of alkali metal sym-(R)dibenzo-14-crown-4-oxyacetates

Solution structures of alkali metal sym-(R) dibenzo-14-crown-4-oxyacetates with R = C10H21 (L1X) and R = H (L2X) have been probed by H-1 and C-13 NMR spectroscopy. Analysis of the diastereotopic nonequivalence changes, Delta delta(AB), especially for atoms remote from the sidearm attachment site, pr ovides insight into the preferred orientation of the sidearm in solution. C ooperative metal ion complexation by the crown ether portion of the ligand and the sidearm is evident for all of the salts in CDCl3. Solvent dependenc e of the structure is noted for the L2X salts. In DMSO-d(6) and D2O, the de gree of interaction between the cation and the crown ether moiety varies wi th the identity of the alkali metal cation. Three different metal ion coord ination arrangements are deduced for L2Li in CDCl3, DMSO-d(6), and D2O. The Li+ is complexed by both the polyether unit and the carboxylate group of t he sidearm in CDCl3. In D2O, the Li+ is coordinated to the polyether unit a nd through one or more water molecules to the carboxylate group of the side arm. In DMSO-d(6), the Li+ does not associate with the crown ether unit.