UV-visible, 1H and 13C NMR spectroscopic studies on the interaction between protons or alkaline earth metal ions and the benzoate ion in acetonitrile

The interaction between protons (H+) or alkaline earth metal ions (Mg2+, Ba2+) and the benzoate ion has been examined in acetonitrile by means of UV-visible, 1H and 13C NMR spectroscopy. The assignments of 13C NMR spectra for the benzoate ion (L−), benzoic acid (HL), and the protonated benzoic acid (H2L+) in acetonitrile were properly performed by means of theoretical calculations, including the influence of the acetonitrile solvent by using the self-consistent isodensity polarized continuum model and the polarized continuum model. It is demonstrated that “strong” interactions of alkaline earth metal ions (M2+ = Mg2+, Ba2+) with the benzoate ion (L−) lead to the formation of mono-charged species, ML+, as well as non-charged species, ML2, in acetonitrile solution: the strong ability in coordination for alkaline earth metal ions is verified.