Year of Award

2014

Document Type

Dissertation

Degree Type

Doctor of Philosophy (PhD)

Degree Name

Chemistry (Inorganic Option)

Department or School/College

Department of Chemistry and Biochemistry

Committee Chair

Edward Rosenberg

Commitee Members

Bruce Bowler, Valeriy Smirnov, Keith Parker

Abstract

The focus of this project has been on the use of mono-diimine ruthenium organometallic complexes, of the general structure [H(Ru)(CO)(L)2(L’)2][PF6] (L=PPh3, DPPENE and L’=Bpy, DcBpy, MBpyC, Phen, AminoPhen) bound to surfaces as luminescent probes. Both biological and inorganic/organic hybrid surfaces have been studied. The complexes were characterized both bound and unbound using standard analytical techniques such as NMR, IR and X-ray crystallography, as well as through several photophysical methods as well.

Initially the study focused on how the photophyscial properties of the complexes were affected by incorporation into biological membranes. It was found that by conjugating the probes to a more rigid cholesterol moiety that luminescence was conserved, compared to conjugation with a far more flexible lipid moiety, where luminescence was either lost or reduced. Both the cholesterol and lipid conjugates were able to insert into a lipid membrane, and in the more rigid environment some of the lipid conjugates regained some of their luminescence, but often blue shifted and reduced, depending on the conjugation site.

Silica Polyamine Composites (SPCs) were a hybrid material developed in the Rosenberg Lab as useful metal separation materials, that could be easily modified, and had several benefits over current commercially available polymers, or inorganic materials. These SPCs also provided an opportunity for the development of a heterogeneous platform for luminescent complexes as either catalysts or sensors. Upon binding of the luminescent Ru complexes to the surface no loss, or major change in luminescence was seen, however, when bound to the rigid surface a significant increase in excited state lifetime was measured. It is likely that through binding and interacting with the surface that the complexes lost non-radiative decay pathways, resulting in the increase in lifetime, however, these interactions do not seem to affect the energy level of the MLCT band in a large way.

With a better understanding of the effects of surface binding on the complexes, the study turned to possible applications, as either sensors or catalysts. Recently the bound complexes have been found to be very useful as toxic metal sensors, as the free amines left on the surface could bind toxic metal ions in close proximity leading to either a quenching or enhancement of the luminescence of the complexes, depending on the metal ion. This process was determined to be a static process, requiring the toxic metal to remain bound to the surface in order to affect the luminescence of the Ru complex. The quenching is thought to be due to a metal-centered electron-transfer reaction, in which the excited-state electron is transferred from the Ru to the toxic metal, but relaxes back to the Ru center. The enhancement of luminescence is due to the external heavy-atom effect, in which heavier atoms mixes MLCT singlet state with the triplet state through spin-orbit coupling.

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© Copyright 2014 Geoffrey Reuben Abbott