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This thesis describes the synthesis, characterization, optoelectronic, and redox properties of boron difluoride hydrazone (BODIHY) dyes. BODIHYs are part of a class of molecular materials whereby chelating N-donor ligands form complexes with a boron difluoride (BF2) moiety, which rigidifies and introduces push-pull electronic structures to the resulting dyes. This thesis demonstrates that structural modifications to the appended substituents on the BODIHY core can be used to drastically tune the optoelectronic and redox properties of the unique complexes. BODIHYs are weakly luminescent in dilute solutions but exhibit enhanced emission in the aggregate- and solid-state due to a phenomenon known as aggregation-induced emission (AIE). AIE-active dyes, such as BODIHYs, have freely rotating substituents such as aryl rings which non-radiatively dissipate energy following electron excitation. In the aggregate state, these substituents are unable to move freely which result in reduced non-radiative relaxation pathways and thus, emission is detected. BODIHYs also exhibit reversible redox chemistry, which was reported for the first time in chapter two, where a paramagnetic BODIHY was observed following chemical oxidation. The results in chapter three describe BODIHY dimers that exhibit two one-electron oxidation and reduction events and explores how push-push, pull-pull, and push-pull electronics alter the optical properties of the dimers. Chapter four describes the first example of a BODIHY polymer that exhibits enhanced emission due to aggregation as well as changes in environment viscosity. Chapters five and six explore the use of BODIHYs as electron acceptors in donor-acceptor and acceptor donor-acceptor molecular architectures where the strength of the electron donor unit is altered. Chapter five focuses on triphenylamine electron donor groups which lead to dual-emission, charge-transfer character, and multiple reversible redox waves. In chapter six, a structure-property relationship is presented whereby altering the size and strength of an electron donor group alters the optoelectronic, redox, and band gaps of the resulting in D-A and A-D-A materials. The work presented in this thesis serves as a basis for the continued development of molecular materials derived from BODIHYs and demonstrates the potential for these materials to be incorporated into optoelectronic-based applications such as organic electronic displays and light-harvesting materials. |
