Conformational analysis of a synthetic carboxylic ionophore in solution by 1H NMR spectroscopy

The 1H NMR spectra of the potassium salt of a synthetic polyether carboxylic ionophore, HO[CH2CH2O(1,2-C6H4)O]4CH2 (1,2-C6H4)COOH (1), in CDCl3 were assigned by two-dimensional NMR methods (2D chemical shift correlation and 2D NOE). The gauche conformer about the C—C bond of the 1,2-dioxyethylene groups of the potassium salt of 1 were found to be predominant from the analysis of the proton-proton vicinal coupling constants. Based on rotamer population analysis, together with nuclear Overhauser effect data, the preferred conformation of the potassium salt of 1 in the solution was estimated.