Effect of the coordination centers and the solvents on the parameters of the 1H and 13C NMR spectra of biology active Zn+2 and Cd2+ acetate mononuclear complexes with chelating 1,10- phenanthroline

Abstract The NMR ¹Н and ¹³С spectra of Zn⁺ ² and Cd²⁺ acetate mononuclear complexes with 1,10-phenanthroline M(phen)n(OAc)₂•2H₂O (M = Zn²⁺ and Cd²⁺, n = 1–3) for their solutions in DMSO-d₆, D₂O and mixture DMSO-D₆–D₂O were studied. The effect of the coordination centers and the solvents on the parameters of the ¹H and ¹³C NMR spectra is considered. It is noted that the chemical shifts of the δH protons of the heteroaromatic rings of 1,10-phenanthroline are sensitive to coordination with Zn⁺ ² and Cd²⁺ ions, but the type of solvent has the greatest effect on the δН. For M(phen)n(OAc)₂•2H₂O (n = 1,2) complexes, the maximum shift to a weak field of δH values occurs for the mixed solvent DMSO-D₆–D₂O. For complexes [M(phen)₃](OAc)₂•2H₂O in the mixed solvent DMSO-D₆–D₂O, on the contrary, there is a very weak shift of the values of δH in a strong field compared with the values for DMSO-D₆ and in a weak field compared with the values in D₂O. The difference in the ¹H NMR spectral pattern for compounds M(phen)n(OAc)₂•2H₂O (n = 1,2) and [M(phen)₃](OAc)₂•2H₂O should be associated with the coordination saturation of the latter, for which the insertion of a solvent – D₂O or DMSO-D₆ into the internal coordination sphere is practically impossible While the complexes M(phen)n(OAc)₂•2H₂O (n = 1,2) are coordination-unsaturated structures and allow solvent molecules to penetrate into their internal coordination sphere. Complexes of Zn⁺ ² and Cd²⁺ with 1,10-phenanthroline were synthesized by complexation reactions.