Influence of metal ions on systems of dimethylsulfoxide-uracil-derivatives: NMR investigations

Summary

The NMR spectra of uracil and some of its derivatives have been investigated using deuterated dimethylsulfoxide as a solvent. The spectral positions of the peaks depend on the electron-attracting or -releasing strength of the substituents: rel. to uracil, the peaks were shifted upfleld in the case of the electron-releasing substituents andvice versa. A plot of the electron affinityvs. the H-3 position exhibits a straigth line. Addition of Cu²⁺ or other metal ions, such as Pe³⁺, Ni²⁺, Co²⁺, Zn²⁺, and Ag⁺, results in a splitting of the N-H protons, the distance of which turned out to be a linear relationship to the inverse electronegativity. K⁺, Na⁺, Mg²⁺, NH₄ ⁺, Cl⁻, NO₃ ⁻, SO₄ ²⁻ had no effect at all. The effect of Cu²⁺ and the substituents as well seems to be mediated by the hydrogen bond formed between the uracil derivative and DMSO.