The aerobic dehydrogenative lactonization of alkenoic acids facilitated by a cooperative nonmetallic catalyst pair is reported. The title procedure relies on the adjusted interplay of a photoredox and a selenium-π-acid catalyst, which allows for the regiocontrolled construction of five- and six-membered lactone rings in yields of up to 96%. Notable features of this method are pronounced efficiency and practicality, good functional group tolerance, and high sustainability, since ambient air and visible light are adequate for the clean conversion of alkenoic acids into their respective lactones. The title method has been used as a case study to elucidate the general mechanistic aspects of the dual selenium-π-acid/photoredox catalysis. On the basis of NMR spectroscopic, mass spectrometric, and computational investigations, a more detailed picture of the catalytic cycle is drawn and the potential role of trimeric selenonium cations as catalytically relevant species is discussed.

This Concept article highlights the development of a novel analytical tool, LED-NMR (a combination of in situ light illumination using a light-emitting diode and NMR spectroscopy) and its variant UVNMR (LED-NMR coupled with UV/Vis absorption spectroscopy), as well as their applications in the mechanistic investigation of light-induced transformations. The utility of these new tools has been demonstrated by providing rich kinetic and structural data of reaction species offering mechanistic insights into photochemical and photocatalytic reactions. Furthermore, NMR actinometry has been recently developed as a practical and simple method for quantum yield measurements. Quantum yield is an important parameter in photoinduced processes, but is rarely measured in practice because of the barriers associated with traditional actinometry. These new tools and techniques streamline measurements of the quantum efficiency while affording informative mechanistic insights into photochemical reactions. We anticipate these techniques will enable chemists to further advance the rapidly emerging photochemistry field. adoption of LED-NMR will make this powerful technique a standard method in the field of photochemistry.

Photochromic compounds like azobenzenes are widely used for the production of stimuli responsive materials. To analyse cascaded azobenzene switching inside a benzene-tricarboxamide (BTA) with three azobenzene moieties in a site-specific fashion, we used in situ irradiation NMR spectroscopy. Four photoisomers can be distinguished by their chemical shifts. Analysis of H,C and N shifts reveals that the configuration of one sidechain has an influence on the chemical shifts of both the other sidechains. Interconversion kinetics upon irradiation with ultraviolet (UV) light as well as molar fractions in photostationary states (PSS) were examined. Analysis of thermal fading of the different photoisomers into the ground state shows that thermal relaxation rates of all three azobenzene moieties behave as if they were independent of each other.

A strategy towards photochromic SI-ROMP homopolymers based on spiropyran and spirooxazine in mesopores is presented and photochromism is systematically investigated using UV-VIS spectroscopy and NMR.

The near-field of surface plasmons is locally confined to nanometer dimensions. Here, we use surface plasmons to initiate polymer-functionalization of mesoporous silica films allowing subsequent ionic permselectivity gating based on polymer charge. We expect this functionalization approach to open a new dimension of functional miniaturization e.g. in nanofluidics.