The utilization of CO via electrochemical reduction constitutes a promising approach toward production of value-added chemicals or fuels using intermittent renewable energy sources. For this purpose, molecular electrocatalysts are frequently studied and the recent progress both in tuning of the catalytic properties and in mechanistic understanding is truly remarkable. While in earlier years research efforts were focused on complexes with rare metal centers such as Re, Ru, and Pd, the focus has recently shifted toward earth-abundant transition metals such as Mn, Fe, Co, and Ni. By application of appropriate ligands, these metals have been rendered more than competitive for CO reduction compared to the heavier homologues. In addition, the important roles of the second and outer coordination spheres in the catalytic processes have become apparent, and metal-ligand cooperativity has recently become a well-established tool for further tuning of the catalytic behavior. Surprising advances have also been made with very simple organocatalysts, although the mechanisms behind their reactivity are not yet entirely understood. Herein, the developments of the last three decades in electrocatalytic CO reduction with homogeneous catalysts are reviewed. A discussion of the underlying mechanistic principles is included along with a treatment of the experimental and computational techniques for mechanistic studies and catalyst benchmarking. Important catalyst families are discussed in detail with regard to mechanistic aspects, and recent advances in the field are highlighted.

Although organic electrosynthesis is generally considered to be a green method, the necessity for excess amounts of supporting electrolyte constitutes a severe drawback. Furthermore, the employment of redox mediators results in an additional separation problem. In this context, we have explored the applicability of soluble polyelectrolytes and polymediators with the TEMPO-mediated transformation of alcohols into carbonyl compounds as a test reaction. Catalyst benchmarking based on cyclic voltammetry studies indicated that the redox-active polymer can compete with molecularly defined TEMPO species. Alcohol oxidation was also highly efficient on a preparative scale, and our polymer-based approach allowed for the separation of both mediator and supporting electrolyte in a single membrane filtration step. Moreover, we have shown that both components can be reused multiple times.

Obwohl die organische Elektrosynthese im Allgemeinen als nachhaltige Methode anerkannt ist, stellt hier die Notwendigkeit zur Verwendung von Leitsalzen einen großen Nachteil dar.Z udem verursachen die vielfache ingesetzten Mediatoren ein weiteres Trennproblem. Vord iesem Hintergrund haben wir die Mçglichkeit zur Verwendung von lçslichen Polyelektrolyten und Polymediatoren untersucht, wobei uns die TEMPO-vermittelte Alkoholoxidation als Modellreaktion diente.Unsere Zyklovoltammetriestudien belegen, dass TEMPO-modifizierte Polymere bezüglichd er Reaktionskinetik durchaus gegenüber dem molekular-definierten TEMPO konkurrenzfähig sind. Auch im präparativen Maßstab zeigt sich unser polymerbasierter Ansatz als verlässlich und effizient, wobei die Abtrennung des Mediators und des Leitsalzes in einem einzigen Schritt mittels Membranfiltration gelingt. Zudem konnten wir zeigen, dass beide Komponenten recyclingfähig sind.

The high suitability of hydrogen silsesquioxane (HSQ) as e-beam resist has long been known. Despite its undoubtedly good and reliable properties, HSQ nevertheless proves to be problematic in certain aspects due to its relatively short shelf-life and the small processing window between coating preparation and exposure. We thus intended to optimize the silsesquioxane with respect to a prolonged shelf-life and larger processing window while retaining all advantages like the high silicon content for high etch resistance and high pattern resolution. Our combined knowledge resulted in the development of the hydrogen silsesquioxane-based e-beam resist Medusa 82 with improved characteristics. Medusa 82 can be processed with HSQ standard procedures but allows for a delay of several weeks between layer preparation and exposure under standard conditions. Medusa 82 resist compositions tolerate storage periods of several weeks at room temperature. In addition, we generated and investigated variants of Medusa 82, which offer the possibility for exposure with less energy to cross-link the resist. Furthermore, weaker alkaline developers can be applied. A postexposure bake of these new Medusa 82 variants provides a significant enhancement of sensitivity and contrast. In this context, applications of Medusa 82 in deep to extreme ultraviolet and grayscale lithography are described. The use of glasslike resists with moderate electron beam sensitivity has the potential to reduce the effort and to simplify the manufacturing process of micro-optical devices that traditionally have to be structured in glass surfaces. The transformation process of Medusa 82 into a glasslike material involves an e-beam exposure, a thermal treatment, or a combination of both. Moreover, the adjustable contrast and sensitivity enable grayscale lithography. Different e-beam exposures trigger a different cross-linking degree within the layer, resulting in height variations after development. A postexposure bake step induces further cross-linking and a complete conversion into silicon oxide.

Requirements for using Poly (2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PolyTEMPO) as an electrocatalyst for the organic electrosynthesis of benzonitrile from benzyl alcohol were investigated. The research results indicated that PolyTEMPO expressed catalytic activity in the electrosynthesis of benzonitrile from benzyl alcohol in the presence of ammonium acetate. The electrosynthesis yield of benzonitrile from benzyl alcohol with PolyTEMPO catalyst reached the maximum value at 35 °C after 18 hours.