One Macrocyclic Ring to Rule the Iron: Harnessing Macrocyclic Unsaturation to Tune the Properties of Organometallic Complexes

The present body of work has focused on the development of the chemistry of iron complexes of macrocyclic ligands, specifically HMC and HMTI. This has proceeded along two distinct, though related, lines. First, metal-alkynyl complexes have been synthesized, and the effects of the macrocyclic ligand on the metal center – and therefore on the metal-alkynyl bond – have been extensively explored. This is first described for a mono- and bis-alkynyl pair in Chapter 2, in which the general structural and electrochemical features of the Fe(HMTI) motif are delineated. In Chapter 3, the detailed characterization of an iron HMC/HMTI family of complexes is described, which is accompanied by spectroelectrochemical (SEC) analyses and extensive DFT and TD-DFT. Finally, as described in Chapter 4, the understanding gained in the aforementioned works is leveraged to control the properties of mixed-valent complexes based on Fe(HMC/HMTI) bis-alkynyl motif, with a motivation to explore fundamental questions for the development of molecular wires.

The second realm of exploration has been concerned with understanding ferrous complexes of HMTI at a deeper level – which species have been previously reported but largely uninvestigated. Collaborative efforts have shown that these FeII(HMTI) species can have unusually long excited state lifetimes under the appropriate conditions, as discussed in Chapter 5. Further (unpublished) characterization of this family of complexes is the focus of Chapter 6, which highlights the relationship between the energy of the charge-transfer absorption band and the nature of the axial ligand.

The novel work outlined above is preceded by introductory material (Chapter 1). This chapter serves to briefly contextualize the body which follows within the landscape of the earlier established (though limited) literature on Fe(HMTI) species. Chapter 1 thus represents an attempt to illustrate the ties throughout what might otherwise (and perhaps still does) appear a disjointed conglomerate of text.