Glossar zu Begriffen mit Bezug zu Kinetik,Thermodynamik und Mechanismen von Polymerisationen

Im Folgenden werden empfohlene Definitionen von grundlegenden Begriffen mit Bezug zu Polymerisationsprozessen vorgestellt. Neuere Entwicklungen im Hinblick auf die Kinetik, die Thermodynamik und die Mechanismen von Polymerisationen machen die Einführung neuer Begriffe und einige Revisionen oder Erweiterungen von Begriffen notwendig, die zuvor im “Compendium of Chemical Terminology” oder im “Glossary of Basic Terms in Polymer Science” definiert wurden.     

Crystallization‐Induced Emission of Azobenzene Derivatives

Most azobenzene derivatives are utilized as well‐defined photoresponsive materials, but their emission properties have not been of great interest as they are relatively poor. Here, we report crystallization‐induced emission (CIE) based on the suppression of the photoisomerization of azobenzene derivatives. Although these molecules show negligible emission in solution, their microcrystals exhibit intense emission from the azobenzene moieties as a result of CIE. Upon rapid precipitation, fine particles with low crystallinity were kinetically formed and underwent CIE over time with a concomitant increase in crystallinity. Furthermore, we demonstrated “photocutting” of an emissive single crystal using a strong laser by a combination of CIE behavior and photomelting based on the photoisomerization of the azobenzene moiety. Our results regarding the CIE behavior of azobenzene derivatives in addition to their photoisomerization can provide a new platform for developing photoresponsive luminescent materials.     

Selectivity of Chemical Conversions: Do Light‐Driven Photoelectrocatalytic Processes Hold Special Promise?

One of the great challenges in chemistry is the development of innovative catalytic processes. In this context, significant opportunities are currently opening up for technologies based on electrocatalysis and photoelectrocatalysis, as these can drive various valuable catalytic redox transformations under very mild conditions. However, many catalytic processes lead to various different products of different value, and the technological attractiveness of catalytic processes depends to a large extent on their selectivity towards a specific desired product. In this Viewpoint, I propose and explore the idea that, due to the distinct features of interfacial energetics at illuminated semiconductors, light‐driven photoelectrocatalytic processes at well‐designed semiconductors represent a particularly attractive platform for the development of highly efficient systems for selective catalytic conversions. The investigations of selectivity and synthetic aspects of photoelectrocatalysis should gain momentum, especially as they also promise commercially viable applications on a more immediate time scale as compared to, for example, the light‐driven production of hydrogen.