Date of Award

2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Materials Science

Committee Chair

Anusree Mukherjee

Committee Member

Carmen Scholz

Committee Member

Emanuel Waddell

Committee Member

Judith Schneider

Committee Member

Shanlin Pan

Subject(s)

Photochemistry., Transition metals., Ligands., Quantum dots.

Abstract

The energy appetite of our global society is enormous with the need only expected to double by midcentury and triple by 2100. The global energy demand calls for diversifying our energy sources and relying more on sustainable energy resources. Transition metals are ubiquitous in nature and central to many organic and biochemical transformations. Activation and catalytic conversion by multielectron redox reactions are crucial for the production of fuels (e.g., hydrogen) or useful chemicals (e.g., organic compounds). In this dissertation we will present our efforts on finding catalysts that can do organic transformations under ambient conditions. We also investigated different multi-component systems to understand the mechanism of electron transfer pathways so that an efficient photosensitizer-catalyst assembly can be designed. The development of efficient and selective hydrocarbon oxidation processes with low environmental impact remains a challenge. Herein we report the synthesis of nickel complexes supported by nitrogen rich tetradentate ligands. The complexes have been characterized by optical spectroscopy, mass spectrometry and elemental analyses. Crystal structures of three complexes have been reported. Oxidative properties of the complexes were studied by their reactivity with two substrates 1,4-cyclohexadiene and 2,4,6-tri-tert-butylphenol in the presence of potassium superoxide. Both sets of reactions led to the oxidation of the substrates and the product yields were quantified. Based on isotope labeling experiments a reaction mechanism was proposed for the oxidation of the phenol by the nickel complexes in the presence of superoxide. Photocatalytic water splitting using solar energy for hydrogen production offers a promising alternative form of storable and clean energy. To develop the photocatalytic system, we need to couple a catalyst for proton reduction to a photosensitizer and understand the mechanism of photoinduced electron transfer from the photosensitizer to the catalyst. We focused on the study of light driven electron transfer kinetics from quantum dot systems made with inorganic chalcogenides in the presence of nickel and copper reduction catalysts. The lifetime of the quantum dots was investigated in the presence of the complexes and absorbance, emission, dynamic light scattering, and electrochemical measurements were performed to gain a deeper understanding of the photoinduced electron transfer process.

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