Date of Award
Program or Major
Doctor of Philosophy
Roy P Planalp
Transition and Group IIB metal complexes of novel ligands derived from cis,cis-1,3,5-triaminocyclohexane (tach) were prepared for structural and biological activity study. Copper(II) complexes of N,N ',N″-trialkylated derivatives of tach [Cu(tach-R3)Cl2] (R = Me, Et, Pr, furanyl, and thiophenyl) were prepared from CuCl2 in MeOH or MeOH/Et2O solvent. The structures of [Cu(tach-R3)Cl2] in the solid and solution (aqueous and methanolic) states were extensively studied by UV-vis and EPR spectroscopies and were consistent to X-ray structure of [Cu(tach-Et 3)Br0.8Cl1.2] which reveals a slightly distorted square-based pyramidal geometry. Displacement of halide ions with water molecules in aqueous media was observed by the band shift to high-energy transition. Catalytic behavior of [Cu(tach-Me3)]2+ in the hydrolysis of activated phosphate diesters in aqueous medium is different from other labile metal complex. Hydrolysis is first-order in phosphate ester and second-order in [Cu(tach-Me3)]2+ suggesting a binuclear complex in which a substrate bridges two Cu(II) ions. Iron-mediated oxidative dehydrogenation of a coordinated ligand was observed in the reactions of Fe(II) and Fe(III) with tachpyr and (+/-)tach(C-Me)3pyr in the presence of O 2 resulting in the formation of a mixture of corresponding mono- and di-imino Fe(II) complexes characterized by 1H NMR, IR, and UV-vis spectroscopies. Further oxidation can be achieved by adding H 2O2 in the case of tachpyr, and by longer exposure of the complex to air, for (+/-)tach(C-Me)3pyr, affording the tris-imino complex. Tachpyr also reveals cytotoxicity toward cancer cells through an iron depletion mechanism. The abilities of tachpyr to complex iron, to reduce intracellular Fe(III) to Fe(II), and to produce hydroxyl radicals is believed to correlate to its cytotoxic effect. First-row transition and Group IIB metal complexes of tachpyr, N,N', N″-tris(2-pyridylmethyl)-cis,cis-1,3,5-triaminocyclohexane, exhibit a metal radius effects on coordination geometry. The tachpyr ligand forms a nearly octahedral complex with the Zn(II) and Ni(II), a tetragonally distorted octahedral complex with Cu(II), an intermediate between octahedron and trigonal prismatic complex with Cd(II), while it forms a nearly trigonal prism complexes with Mn(II) and Hg(II). Tach-Me3pyr, N,N',N″-trimethyl- N,N',N″-tris(2-methylpyridyl)- cis,cis-1,3,5-triaminocyclohexane, forms a distorted octahedral complexes with Ni(II) and Zn(II) while it forms a Jahn-Teller distorted Cu(II) complex. The steric effects of methyl groups govern the coordination of metal complexes of tach-6-Mepyr, N,N',N ″-tris(6-methyl-2-methylpyridyl)-cis,cis-1,3,5-triaminocyclohexane, affording a nearly octahedral geometry with the Zn(II) Ni(II) Co(II) and Mn(II) metal ions, while it forms a distorted trigonal bipyramidal complexes with Cu(II) as a consequence of a twisted pendent arm away from Cu(II) ion.
Park, Gyungse, "Transition metal complexes of novel ligands derived from the cis,cis-1,3,5-triaminocyclohexane (TACH) framework: Structural and biological studies" (2000). Doctoral Dissertations. 2143.