21134a

Adaptive Ligangden und Molekulare (Elektro-)Katalyse

Biprajit Sarkar, Arijit Singha Hazari

Zusätzl. Angaben / Voraussetzungen

This lecture can be taken as part of

a) the Specialization Module in Inorganic Chemistry:
- 2 hours/week lecture (attendance recommended but not compulsory)
- 2 hours/week seminar (select dates, attendance mandatory)
- presentation on a pre-determined topic in the seminar
- written exam: 60 minutes, gradded

b) Modern Aspects in Chemistry:
- 2 hours/week lecture (80% attendance mandatory)
- written test: 60 minutes, pass/fail Schließen

Kommentar

Electrocatalysis is a transformative technology that is already contributing, and more importantly, has the potential to contribute to conversion of small molecules for energy related research, or for improving sustainability in organic synthesis. A special subbranch of the broad area of electrocatalysis is molecular electrocatalysis. In this sub discipline, the whole breadth of ligand design can be made use of to tune molecular electrocatalysts, and hence to tune reactivity and selectivity of a variety of chemical transformations by making use of electrocatalysis. In addition, the idea of tuning catalytic reactivity and selectivity through the "simple" change of the applied potential makes electrocatalysis a very attractive field. The so-called adaptive ligands that can "adjust" their electronic properties as a function of the "demands" from the central metal ion, are privileged ligands in molecular (electro)catalysis. Apart from tuning the central catalytic unit, such adaptive ligands can sometimes also actively participate in bond activation reactions, making the catalytic process more efficient.

In this lecture, the concept of adaptive ligands will be explored through illustrative examples, with emphasis on their ability to dynamically tune the electronic and steric environment around metal centres. In addition to their primary coordination role, adaptive ligands often interact with the broader secondary coordination sphere—incorporating features such as pendant proton relays, hydrogen-bond donors, and electrostatic groups—which are now recognized as key design elements for enhancing selectivity, facilitating proton-coupled electron transfer (PCET), and breaking activity–selectivity scaling relationships.

The basic principles of molecular electrocatalysis will be elaborated, including critical parameters like turnover frequency (TOF), overpotential, Faradaic efficiency, and methods for their quantitative determination. Case studies will include the molecular activation of CO2, O2, and H2, showcasing how both first- and second-sphere ligand design affects mechanistic pathways. In parallel, attention will be paid to common modes of catalyst deactivation—such as torsional strain, ligand oxidation, or demetallation—highlighting how stability considerations influence catalyst lifetime and turnover.

The course will also explore the expanding role of molecular electrocatalysis in synthetic organic chemistry, focusing on transformations like borrowing hydrogen, transfer hydrogenation, semi-hydrogenation of alkynes, dehalogenation, and C–C bond formation reactions. These examples will be used to illustrate how electrochemical potential serves as a unique and tunable parameter to control chemo-, regio-, and stereoselectivity. Mechanistic elucidation tools—including electroanalytical techniques and spectroelectrochemical methods—will be introduced, alongside brief insights into how computational modelling and data-driven approaches are shaping the next generation of ligand and catalyst design. Schließen