Download (over) Candidate: Agozie Nnaemeka Oyeamalu For the degree of

Candidate:
For the degree of:
Department:
Agozie Nnaemeka Oyeamalu
Doctor of Philosophy
Chemistry
Title:
Structures of Metallacarboranes and Coordination
Complexes: Coordination Sensors Based on
Rhodamine B and Quinolines
Committee:
Dr. Ekkehard Sinn, Chair
Dr. Sherine Obare
Dr. Donald Schreiber
Dr. Daniel Cassidy
Time/Place:
Thursday, April 20, 2017
8:30 to 10:30 a.m.
1220 Chemistry Building
Rhodamine-based ligands that can complex different metals have
been designed and synthesized for this study. Using Rhodamine B as starting
material, quinoline precursors were synthesized and characterized, as well as
successfully carrying out the oxidation of methyl and aldehyde groups on the
quinoline ring, and on the hydroxyl moiety of the quinoline spirolactone ring.
These turn-“on-off” rhodamine fluorescence probes sense Cr3+ and Ni2+ with
high selectivity and sensitivity. These probes can be applied to detect other
metal ions that are present in chemical, biological and environmental
settings. They are designed to fluoresce when bonded to ions such as
cyanide in detecting warfare agents, as well as trivalent chromium, aiming to
(over)
detect at low concentration levels. Cr3+ is considered an important toxic
environmental pollutant, and nickel is a potential contaminant in
pharmaceuticals. Detection of Cr3+ and Ni2+ at low concentrations will help
combat their adverse health effects, such as cancer or neurodegenerative
diseases.
X-ray diffraction of single crystals is another research area that has
gained scientific attention over the course of the last few decades. This area
of research combines the fundamental theories and applications based on
diffraction and statistics in order to provide a complete understanding of the
molecular and geometric characteristics of molecules. In this study, we were
able to solve structures of new metallacarboranes and other complexes via
X-ray crystallography. This resulted in specifically two crystallographically
independent molecules in the unit cell complex of the metallacarborane
cluster framework [3,3-(CO)2-3-NO-closo-Re(8-O(CH2)2O(CH2)2I-3,1,2-C2B9H10)].
The ReC2B9 moiety is comprised of the usual closo-icosahedral framework
with an η5 –coordinated Re center. Such rhenacarborane derivatives can be
prime candidates for use as drug-delivery vehicles of amino acids or small
peptides across the blood-brain barrier, which might otherwise not be easily
transported.
X-ray studies were carried out on some new metal complexes,
designed and synthesized for anti-cancer applications. The results of this
study show that the actual structures were different than those intended in
the original synthetic design. Additionally, the actual X-Ray structures are
compatible with the synthetic design determined, and are predictable and
expected based on structural consideration. The intended design included
two adjacent 8-membered rings, which would show a significant degree of
steric strain. However, the actual structures contained two adjacent 5membered rings and constitute a sterically more relaxed system.