Photochemical Sciences Ph.D. Dissertations

Photochemistry of dipyridyl-phenanthrenedioxin-copper complexes

Date of Award

2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Photochemical Sciences

First Advisor

R. Marshall Wilson (Advisor)

Second Advisor

Alexander Tarnovsky (Committee Member)

Third Advisor

Mikhail Zamkov (Committee Member)

Fourth Advisor

Howard Cromwell (Committee Member)

Abstract

Metal complexes of heterocyclic ligands have shown significant anti-tumor effects. DNA molecules are known to be a target of cancer drugs due to their ability to non-covalently bind and interact with biomolecules. There are several common DNA binding modes: intercalation of a molecule between two nucleic acid base pairs, electrostatic binding to a negatively charged backbone, and binding to a groove. Of these three binding modes, intercalation between DNA base pairs is known to be the strongest. Most of the metallo-complexes contain in their structure a flat aromatic moiety, and positively charged metal center.

Copper complexes have a redox-active center that provokes oxidation processes of DNA because of their ability to function under physiological conditions. Oxidation is the main pathway for cleavage of the DNA molecule. There have been developed and characterized a great number of copper nucleases. Alteration of a ligand molecule will offer ability to vary properties of the complex, such as; binding to specific sites of DNA, cleavage pathways, and water solubility. We have investigated in 6’,6’-di(2-pyridyl)-9,10-phenanthren-1’,4’-dioxin as a ligand for copper complexes. It has a planar phenanthrene moiety and two pyridine rings on one carbon atom which allows formation of donor acceptor complexes between unshared electron pairs on the nitrogen atoms and vacant orbitals on a copper(II) ion.

(DPhPD)2-Cu(II) (1) complex is easily oxidized after exposure to a UV/Visible light. One of the pathways is to form a radical-cation on the phenanthrene ring (2) by transferring an electron through the pyridine rings to the cupric ion to reduce it to Cu(I). The resulting species undergoes rearrangement to form phenanthrene orthoquinone (3) and radical-cation on the dipyridinyl olefin (4) with following back electron transfer from copper to form olefin (5).

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