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Doctoral Dissertation Announcement
Candidate: Lars Kohler
Doctor of Philosophy
Title: Preparation of 1,10-Phenanthroline Derivatives with B-Ring Functionalization and Their Application
Dr. Elke Schoffers, Chair
Dr. Silvia Rossbach
Dr. Ekkehard Sinn
Dr. James Kiddle
Date: Friday, March 18, 2011 3:00 p.m. to 5:00 p.m.
1260 Chemistry Building
1,10-Phenanthroline and its derivatives are very interesting compounds for applications in organic and inorganic chemistry as well as in biology and medicinal chemistry. Recent examples include their use in chiral catalysis, bioaffinity assays, medicine and sensors. This research focused on the synthesis of novel 1,10-phenanthroline derivatives that were functionalized in 5- and 6-position. The long term goal is their application as catalysts in asymmetric reactions, as bioactive molecules or as sensors to detect harmful chemicals such as warfare agents and environmental pollutants.
5,6-Dihydro-1,10-phenanthrolines were prepared via epoxide opening with oxygen and nitrogen nucleophiles. The corresponding products were obtained as a mixture of enantiomers or diastereomers depending on the nature of the nucleophile. Racemic mixtures were resolved employing lipase-catalyzed transesterification reactions, whereas diasteromeric mixtures were separated using column chromatography or crystallization. The stereochemistry was assigned via circular dichroism, X-ray and NMR. The complexation behavior towards transition metals was studied by reacting selected ligands with copper(II) and nickel(II) salts, and by analyzing them via X-ray crystallography.
B-Ring functionalized 1,10-phenanthroline derivatives that contained a fully conjugated phenanthroline scaffold were synthesized via oxidation and dehydration reactions of 5,6-dihydro-1,10-phenanthrolines.
We tested the antimicrobial activity of some 1,10-phenanthrolines and focused on the opportunistic pathogens Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa using disc diffusion assays. We found that a fully planar phenanthroline moiety was required for increased antimicrobial effects.
The optoelectronic properties of several re-aromatized compounds were investigated. We found that 5-amino-1,10-phenathroline derivatives possessed relatively high quantum yields and solvochromatic shifts due to their intramolecular charge transfer character. Measurements showed that the oxazoline derived from oxidation of 2-hydroxybenzylamine exhibited dual fluorescence. The low-energy emission band was associated with a structural change in the excited state caused by an excited state intramolecular proton transfer.