Doctor of Philosophy
Prof. Joe Gilroy
This thesis describes the synthesis and characterization of a new family of fluorescent and redox-active BF2 complexes of formazanate [R1-N-N=C(R3)-N=N-R5]− ligands. The complexes were easily synthesized in two high-yielding steps, from inexpensive starting materials and readily purified by conventional methods. The properties of the resulting complexes can be tuned through structural variation – for example, appending electron donating or withdrawing substituents, or extending π conjugation. These methods of structural variation can bathochromically or hypsochromically shift the maximum absorption and emission wavelengths, vary the quantum yields, and allow for tuning of the reduction potentials. Using these methods, the properties of these complexes were optimized for use as fluorescence cell-imaging agents, and efficient electrochemiluminescence emitters.
In order to expand the scope of this chemistry, copper-assisted azide-alkyne cycloaddition (CuAAC) chemistry was used to further modify the BF2 formazanate scaffold. Using this method, benzyl groups were appended to the BF2 complexes, which showed that the reaction proceeded cleanly, and that the resulting products had red-shifted wavelengths of maximum absorption and emission, and increased fluorescence quantum yields. Using the same strategy, a tetraethylene glycol based azide imparted water solubility, and the resulting complex was used in fluorescence cell-imaging experiments. Additionally, ferrocene moieties could be appended, which quenched the fluorescence of the resulting complex. Upon oxidation of the ferrocene groups, the fluorescence was regenerated allowing for these compounds to be used as redox sensors. Finally, CuAAC was used to synthesize copolymers of BF2 formazanate complexes and 9,9-dihexylfluorene. The resulting polymers had low band gaps (Eg = 1.67 eV) and good film-forming properties, paving the way for their use in organic photovoltaics.
Finally, reaction of an o-phenol-substituted formazan with BF3•OEt2 and NEt3 resulted in a complex reaction mixture, which contained 5 BN heterocycles with unprecedented connectivity and interesting optical and electronic properties. Two of the most unique complexes were selected, and their chemical reduction products – a stable anion, radical anion and diradical dianion were studied in detail.
Combined, this work has opened up an entirely new area of molecular materials with application in a variety of fields. This thesis describes the details of the work described above.
Barbon, Stephanie M., "Structural Modification, Polymerization and Applications of Boron Difluoride Formazanates" (2017). Electronic Thesis and Dissertation Repository. 4611.