Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Chemistry

Supervisor

Gilroy, Joe B.

Abstract

This thesis describes the synthesis and characterization of group 13 (boron and aluminum) and group 14 (silicon, germanium, and tin) complexes supported by chelating formazanate [R1-N-N=C(R3)-N=N-R5]‒ ligands. The resulting complexes are redox-active and often luminescent. Chapters two to four describe the synthesis and characterization of boron formazanate adducts. The work in these chapters demonstrates that through structural modification of the formazanate ligand, solid-state- and NIR photoluminescence can be achieved. Furthermore, the formation of an oxoborane (B=O) afforded a highly photoluminescent formazanate adduct due to the structural rigidity imposed by the B=O bond. These results highlight the potential of boron complexes of formazanate ligands as promising candidates for use in light-emitting technologies and as dyes for cell imaging studies. In addition, the turn on photoluminescence induced by B=O bond formation represents an innovative design criterion for the realization of unprecedented functional molecular materials.

Chapter five describes the synthesis and characterization of a family of aluminum formazanate complexes supported by phosphine oxide donors. The above-mentioned complexes were redox-active and strongly absorbing in the visible region. One derivative was photoluminescent and its electrochemiluminescence properties were examined. The results in this chapter demonstrate the potential of six-coordinate aluminum formazanate complexes as redox-active and/or luminescent functional materials.

Lastly, the redox-active nature of the formazanate ligand was exploited in chapter six. This chapter describes the synthesis of group 14 formazanate complexes and their conversion to stable radicals via chemical reduction. The radicals were stabilized by geometric and electronic effects, due to the square-pyramidal coordination geometry adopted by the group 14 atom within the heteroatom-rich framework of the formazanate ligand. The results presented in this chapter demonstrate that stable radicals can be realized through judicious ligand design and in the absence of appreciable steric bulk.

Combined, this work demonstrates the utility of formazanates as a versatile ligand framework which can be used to support group 13 and 14 elements in different coordination geometries (e.g., trigonal planar, tetrahedral, square-pyramidal, and octahedral). Furthermore, owing to the optoelectronic properties of the resulting complexes, main-group formazanate complexes are promising candidates for use in organic electronics and for biomedical imaging.

Summary for Lay Audience

This thesis describes the preparation and characterization of new compounds which can absorb and emit different colours of light. These compounds can also store electrical charge carriers (electrons) and subsequently donate them under the appropriate conditions. The combination of these two traits affords materials with potential application in organic electronics and biological imaging. Chapters two to five explored structure-property relationships of these types of compounds to better understand their properties from a fundamental point-of-view. Structural modification of these compounds afforded materials that emitted light in solution or in the solid state. The latter is highly desirable in the field of organic electronics, where materials that emit light in the solid state can be used in display technologies such as organic light-emitting diodes (OLEDs) found in television and cell phone displays. Further structural modification of these compounds afforded highly emissive materials due to the incorporation of a fragment which increased the rigidity of the molecule, as well as molecules that emitted light in the near-infrared (NIR) region. Emission in the NIR region is particularly desirable for biological imaging applications due to minimal interference from biological tissue in this region. Chapter six describes the synthesis and characterization of highly reactive species called radicals. Radicals are reactive because they contain one or more unpaired electron(s). These molecules were stabilized by effectively spreading out the unpaired electron across the entire molecule as opposed to protecting it with bulky groups. This result is important and demonstrates that through careful design, highly reactive species can be stabilized. Combined this work demonstrates that interesting and desirable properties can be realized through judicious molecular design. The materials presented in this thesis are promising candidates for use in organic electronics and for biological imaging.

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