Chemistry Guest Seminars

Abstract:  One of the primary barriers to the large-scale implementation of intermittent renewable energy sources such as solar and wind is effective energy storage. The selective electrochemical reduction of CO2 in the CO2 reduction reaction (CO2RR) is a crucial strategy for storing energy from intermittent energy sources in the form of chemical bonds (e.g. solar fuels). Current state-of-the-art solid-state catalyst materials produce useful products such as methanol or ethylene, but typically do so non-selectively with a variety of gaseous and liquid products including H2 from competitive water reduction. Alternatively, molecular catalysts show promise for more selective reduction of CO2 to single products, typically CO or formic acid, but usually perform with lower overall activity compared to solid-state analogues. My research group is focused on the development of new catalytic systems that reduce CO2 with the selectivity of molecular catalysts but operate with the activity of solid-state catalytic materials.

In this talk, I will present some of our recent studies exploring the use of polymer encapsulation to control the chemical environment surrounding molecular electrocatalysts in order to increase catalytic activity and selectivity for the CO2RR. In particular, I will demonstrate that encapsulating cobalt phthalocyanine (CoPc), a mediocre CO2RR catalyst, within an encapsulating polyvinylpyridine polymer leads to a dramatic increase in the activity and selectivity for the CO2RR. Using a combination of electroanalytical and spectroelectrochemical approaches, I will illustrate how the encapsulating polymer surrounding the CoPc center modulates the primary, secondary, and outer coordination sphere of the catalysts, and I will discuss how modifying these coordination spheres has profound impacts on the catalytic activity, reaction selectivity, and mechanism of CO2 reduction.

The Scott group conducts both fundamental and applied research in reactions, surface chemistry, and catalysis. Our goal is to understand the interactions and transformations of molecules at gas-solid and liquid-solid interfaces by creating highly uniform active sites. We use advanced techniques in organometallic and coordination chemistry, surface science, spectroscopy, kinetics, mechanistic analysis and modeling to investigate, design and reengineer heterogeneous catalysts. Our group includes both chemical engineering and chemistry students, working to solve important current problems at the interface of chemistry and reaction engineering.

Abstract. Transition metal oxo complexes, particularly those of later transition metals, have been cited as important intermediates in processes such as C-H hydroxylation and oxygen evolution. In general, however, these species are highly reactive and difficult to isolate and study. In this talk I will present our laboratory’s efforts at isolating and studying late transition metal oxo complexes. We have found that use of pseudo-tetrahedral geometries enables the isolation of an unusual terminal Co-oxo complex. The reactivity of this species towards C-H activation is markedly different than that observed for the majority of other systems and provides experimental evidence for a new mechanistic scenario dubbed "asynchronous" CPET. Finally, the possible relevance of related Co and Ni complexes in this system towards O-O bond formation will be discussed.

Abstract. Alzheimer’s and other neurodegenerative diseases are chronic conditions affecting millions of individuals worldwide. Although neurodegenerative diseases differ in the symptoms exhibited, oxidative stress is a consistent component described in the development of these brain-based diseases. Despite efforts that have shown promise of regulating oxidative stress in preventing or treating other diseases, there still remains a great need to produce new therapeutic molecules capable of affecting neurodegenerative diseases that involve oxidative stress and to develop an understanding of the activities observed. Therefore, innovative strategies to develop drug candidates that overcome oxidative stress in the brain are needed. To target these challenges, a new, water soluble pyridinophane 12-membered tetra-azamacrocycle L4 was designed and produced using a building block approach. L4 was shown to have dramatically enhanced antioxidant activity and increased biological compatibility in a neuronal cell line compared to parent molecules reported previously. Moreover, L4 was determined to have positive pharmacological characteristics such as an ideal pI = 7.4 and high metabolic stability in Phase I &II models. The Cu(II) complex of L4 was evaluated by X-ray diffraction and cyclic voltammetry to show the modes of antioxidant activity derived from a number of assays. As such, L4 shows how improvement of lead compounds has potential for the treatment for neurodegenerative diseases where oxidative stress plays a substantial role.

Abstract:  In response to rapidly increasing energy storage demands of consuming electronics, electrical vehicles, electrical grids, and renewable energy integration, there is an urgent call for advanced rechargeable batteries with superior energy storage performance and more affordable material costs compared to existing battery technologies. The first part of this presentation will cover our recent effort in developing new battery chemistries towards sustainable and economical electrochemical energy storage. Through rational molecular engineering, we have designed and applied redox active molecules including viologen (anolyte), quinone (anolyte), TEMPO (catholyte), ferrocene (catholyte), and ferrocyanide (catholyte) for developing aqueous organic redox flow batteries (AORFBs). The chemistry and battery performance of redox active molecules will be discussed in detail. In addition, extended from our RFB project, we have employed redox active molecules as electrocatalysts for both energy and chemical conversions. In the second part of this presentation, I will share our recent success in developing Ni-catalyzed electrochemical C-C bond cross-coupling reactions with good reaction efficiency and practical applications while only using bench stable substrates and catalysts. Particularly, this presentation emphasizes that in-depth mechanistic understandings of redox active molecules play crucial roles in developing advanced organic redox flow batteries and electrocatalysis methodologies.