Ligand influences on the photoinitiated binding of small molecules to synthetic copper and heme-copper complex systems

The primary 1:1 interactions of copper(I) ion and dioxygen still gain much interest due to their potential catalytic roles in synthetic and biological systems. However, detailed analysis has often been prevented by the instability of such adducts. Investigations of such reactions are often limited to fast spectroscopic monitoring as is the focus of the work discussed herein. Through purposefully designed ligand frameworks and low-temperature manipulations, the kinetics and thermodynamics of 1:1 Cu/O2 and Cu/CO complex formation are observed and measured through transient absorbance laser flash photolysis.;In Chapter 1, the bioinorganic chemistry of the copper-carbon bond within the framework of copper proteins and other relevant systems is overviewed. In particular, the utility of “Cu-CO” and “Cu-CN” moieties for investigation of active site structures and mechanisms are discussed. For example, carbon monoxide has long been used as a redox-inactive surrogate for O2.;In Chapters 2, 3, and 5, the kinetics and thermodynamics of CO and O 2 binding to various tripodal copper(I)-carbonyl species that possess tetradentate ligands with identical tridentate core structures and one variable donor moiety are discussed. A purely tridentate ligand system was also employed for comparison. In Chapter 2, systematic changes in the electron-donating ability and chelate ring-size were examined. The effort advanced our understanding of the coordination environment required for desirable photodissociation chemistry. In Chapter 3, changes in the N-donor moiety resulted in different O2 -binding reaction mechanisms during the formation of the cupric-( end-on)-superoxo species. In Chapter 5, variation in the donor atom chelate allowed for the transient formation of a cupric-(side-on)-superoxo species to be observed and measured for the first time. Such species are believed to result in hydrogen atom abstraction chemistry, perhaps relevant to the C-H bond activation chemistry reported in Chapter 4.;In Chapter 7, the photorelease of nitric oxide and carbon monoxide from a synthetic heme species in the presence of copper complexes results in small molecule migration to copper(I) before returning to iron(II). In addition, the photorelease of NO from an iron(III)-nitrosyl species and generation of a photoreduced excited state species is examined. In Chapter 6, chlorine atom (Cl·) transfer from iron(III)-to-copper(I) is discussed.