The photochemistry of platinum terpyridines and the investigation of copper porphyrins in hairpins

Denise Kristina Crites, Purdue University

Abstract

The work presented in this thesis spans three projects, the first two chapters involve platinum terpyridines and their photochemistry while the last chapter deals with copper porphyrins and their interaction with DNA hairpins. All three projects utilize emission spectroscopy hence much of the effort centered on understanding the photophysics behind the luminescent complexes. Chapter 1 describes some novel platinum terpyridines which have terpyridine ligands that have been substituted in the 4′ position with electron donating or electron withdrawing groups. Studies of the excited states of these complexes lead us to believe that our systems have a mixing interaction between the metal-to-ligand charge transfer state (MLCT) and an intra-ligand state. Consequently the complexes have much longer lifetimes than the parent complex in fluid solution. The excited state was also probed using Lewis bases which quench the emission. We found that very similar platinum terpyridine derivatives had different quenching rates, and different quenching kinetics. The excited states involving electron-withdrawing groups have quenching rates that are near diffusional levels, while those with electron-donating groups are much harder to quench. The last project involves a water soluble copper(II) porphyrin that associates with DNA hairpins. Many researchers have found that a porphyrin like Cu(T4), where T4 is the deprotonated form of meso-tetrakis(4-(N-methylpyridiniumly))porphyrin, is very selective in its mode of binding to DNA. When the DNA is guanine/cytosine rich the porphyrin intercalates, but if the DNA is adenine/thymine rich the porphyrin undergoes groove binding. We have discovered that the mode of binding depends upon the rigidness of the DNA. In particular, deletion of hydrogen bonds by replacing guanine with inosine can give rise to a dramatic shift in the mode of binding.

Degree

Ph.D.

Advisors

McMillin, Purdue University.

Subject Area

Chemistry

COinS