Affiliations: Department of Chemistry, The College of William & Mary, Williamsburg, VA, USA | Department of Chemistry, Howard University, Washington, DC, USA
Note: [] Present address of Steven M. Berry: Department of Chemistry, University of Minnesota, Duluth, MN, USA
Abstract: The coordination chemistry of divalent zinc triad metal ions with N-(2-pyridylmethyl)-N-(2-(methylthio)ethyl)amine (L) was investigated by X-ray crystallography and proton NMR. Chloride salts yielded non-homologous M(L)Cl2 complexes. Hg(L)Cl2 and Zn(L)Cl2 were five-coordinate monomers with distorted square pyramidal and trigonal bipyramidal geometries, respectively. Cd(L)Cl2 formed a six-coordinate polymer with a distorted octahedral geometry. These complexes had similar nearly temperature independent proton NMR spectra suggesting structural differences between them were less extensive in solution due to fluxional processes. Although 1:1 metal to ligand complexes were most thermodynamically stable for the chloride salts at all [M2+]/[L], the thermodynamic stability of [M(L)(NCCH3)x]2+ only exceeded that of [M(L)2]2+ when [M2+] ≥ [L] with perchlorate salts. Slow intramolecular and intermolecular exchange conditions for [M(L)2]2+ and slow intermolecular exchange conditions for [M(L)(NCCH3)x]2+ were found on the proton chemical shift and in some cases J(M1H) time scales. Strong interactions between divalent zinc triad metal ions and thioether ligand components at physiologically relevant temperatures suggest interactions with methionine should be considered in developing a more complete understanding of the bioactivities of these metal ions.
