Date Awarded

2023

Document Type

Thesis

Degree Name

Master of Science (M.Sc.)

Department

Chemistry

Advisor

Deborah C Bebout

Committee Member

Robert D Pike

Committee Member

William R McNamara

Abstract

The complexes of group 12 elements are subjects of incredible interest due to differences in their bioactivity. Zinc is an essential element of life and is required for many bodily processes including gene production, growth, and the immune response. Cadmium and mercury are both toxic elements to humans. Part of their activity is due to their ability to replace zinc metal centers. Synthesis of new group 12 complexes can provide insight regarding their bioactivity and how replacement of metal centers can affect the structure of enzymes. In this thesis, the preparation and characterization of two sets of group 12 complexes is described. One set of new complexes are cadmium and mercury complexes of the N3S ligand 2-[bis(2-pyridinylmethyl)amino]ethanethiol (L1H) with chemical formulas [Cd(L1)Cl]2·benzene (1) and [Hg(L1)Cl] (2). They are compared with the known complex [Zn(L1)Cl] (3). The new complexes were thoroughly characterized using X-ray crystallography, XPRD, 1H NMR, elemental analysis, and IR. Compound 1 crystallized in the triclinic space group P-1 with an octahedral coordination geometry. The metal ions of 1 were bridged by a pair of ligand thiolate groups. Mononuclear compound 2 crystallized in the monoclinic space group P21/c with mixed square pyramidal/trigonal bipyramidal geometry (τ = 0.44). Both complexes are stabilized by significant offset face-to-face π−π and edge-to-face σ−π interactions between the pyridyl rings, and for 1, between the pyridyl rings and solvent benzene in the unit cells. Significantly, both complexes exhibit heteronuclear coupling in the 1H NMR at -40 °C between the metal centers and specific ligand protons indicating slow ligand exchange on the coupling constant time scale and unusual stability for thiolate complexes of these metal ions. The other set of isolated complexes are bis-tridentate chelates of Zn(ClO4)2, Cd(ClO4)2, and Hg(ClO4)2 with two equivalents of bis(2-pyridylmethyl) ether (L2). The complexes were characterized using X-ray crystallography, IR, 1H NMR, and TGA. [Zn(L2)2](ClO4)2·CH3CN (4) and [Cd(L2)2](ClO4)2·CH3CN (5) crystallized in the monoclinic space group P21 with meridional octahedral geometry. [Hg(L22)](ClO4)2 (6) crystallized with approximately C2 symmetric trigonal prismatic geometry. 1H NMR of 3 at 40 °C show heteronuclear JHgH coupling, and lacks the geminal splitting of methylene protons that would be expected for the solid-state structure. The complexes were compared to other bis-tridentate chelates of bis(2-pyridylmethyl) ligands with the central oxygen of L2 replaced by other heteroatoms.

DOI

https://dx.doi.org/10.21220/s2-ytgp-2895

Rights

© The Author

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