Structures of Metallacarboranes and Coordination Complexes: Coordination Sensors Based on Rhodamine B and Quinolines
Date of Award
Doctor of Philosophy
Dr. Ekkehard Sinn
Dr. Sherine Obare
Dr. Donald Schreiber
Dr. Daniel Cassidy
Rhodamine B, chemosensors, carborane, metallacarborane, coordination complexes, florescence
Rhodamine-based ligands that can complex different metals has been designed and synthesized. Using Rhodamine B as starting material, we synthesized and characterized quinoline precursors as well as successfully carried 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 were designed to fluoresce when bonded to ions such as cyanide in detecting warfare agents, as well as trivalent chromium, aiming to 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. They combine 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 n5 –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 show that the actual structures were different than those intended in the original synthetic design. We show that the actual X-Ray structures are compatible with the synthetic design determined are actually 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. On the other hand, the actual structures contained two adjacent 5-membered rings and constitute a sterically more relaxed system.
Oyeamalu, Agozie Nnaemeka, "Structures of Metallacarboranes and Coordination Complexes: Coordination Sensors Based on Rhodamine B and Quinolines" (2017). Dissertations. 3129.