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.