Synthesis, Characterization, and Applications of Group 13 and 14 Complexes of Chelating Formazanate Ligands
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.