ABSTRACT Radical anions constitute an important class of reactive intermediates. Here, we investigate the suitability of electrospray‐ionization (ESI) mass spectrometry for their qualitative and quantitative analysis. To this end, we have probed solutions of 14 different benzoquinones and nitrobenzenes in the presence or absence of the reductant CoCp 2 . The latter greatly helped in the formation and detection of radical anions, but even without, analytes of sufficiently high electron affinity could accept an electron upon cathodic reduction during the ESI process and, thus, became observable. Analytes with low electron affinities escaped from detection because the corresponding radical anions did not form to a sufficient extent and/or underwent electron detachment during the ESI process and the consecutive ion transfer. Furthermore, we studied the effect of the analyte concentration, different reducing agents as well as the solvent and demonstrated the utility of the present approach for the mechanistic elucidation of reactions involving radical anions.

ABSTRACT A synthetic procedure for the preparation of isocyanide cyclopentadienone iron complexes using the corresponding tricarbonyl complexes and primary amines as starting materials is described. By transforming the primary amines into deprotonated phosphoramidates or silyl amines, the CO ligands can be replaced by CNR ligands by abstracting the CO oxygen atom and replacing it with an NR fragment, with concomitant formation of phosphates or silanols as the thermodynamic driving force. The phosphoramidate route, using RNHP(O)(OEt) 2 , works well for R = alkyl, but fails for R = aryl, presumably due to the reduced nucleophilicity of the intermediate deprotonated phosphoramidate. Aromatic isocyanide ligands are accessible by using silyl amines ArNHTMS (Ar = aryl, TMS = trimethylsilyl) instead. The disclosed procedure has the advantage that the free isocyanide ligands themselves do not need to be isolated, which circumvents the use of strongly unpleasant smelling chemicals. Catalytic transfer hydrogenation reactions show that, under the same reaction conditions, the monoisocyanide complexes perform significantly worse than the corresponding tricarbonyl complexes. Kinetic monitoring revealed that fast catalyst decomposition is responsible for the lower performance. The reaction mechanism of the C≡O/C≡NR transformation was additionally investigated by DFT calculations.

ABSTRACT The spatiotemporal control of complex molecular systems, such as chemical reaction networks (CRNs), requires reagents and reactive species that can be activated both efficiently and precisely. The design of CRNs has gained momentum as a strategy to investigate synthetic non‐equilibrium systems that mimic key features of biological processes operating far from thermodynamic equilibrium. In this study, we present a novel photocleavable and water‐soluble glucose–coumarin glycoside that bridges photochemical activation with chemical fuel‐driven reactivity. During the optimization of the peracetylated glucose–coumarin glycoside synthesis, we elucidate the reaction mechanism of the Koenigs–Knorr glycosylation and identify the most likely rate‐limiting step as the reversible formation of the orthoester. The photochemical release of glucose was subsequently used to drive an established model CRN based on glucose oxidase, enabling light‐triggered acidification of the aqueous environment. Given the high water solubility of the coumarin‐protected glucose derivative, our approach provides a versatile and easily implemented method for regulating pH‐responsive processes and assemblies through precise optical control, in a range of aqueous buffered media.

ABSTRACT Aryl and heteroaryl phosphonium salts have recently grabbed the attention of synthetic organic chemists as excellent substrates to obtain functionalized (hetero)arenes. The phosphonium moiety renders the adjoining carbon site electrophilic; therefore, they are good candidates for nucleophilic substitutions. The weakness of the C─P + bond paves the way for their activation via single electron reduction and thereby furnishing (hetero)aryl radicals for further functionalization. However, a rather intriguing but underexplored mode of activating the phosphonium salts has been via nucleophilic attack on the P + ‐center, resulting in the formation of the penta‐coordinated phosphorane intermediates. These transient intermediates readily undergo fragmentation and give rise to (hetero)aryl anions suitable to be functionalized by reacting with appropriate electrophiles. Here we document the history and the recent advances of this umpolung strategy to project its potential for future applications.

ABSTRACT Electron donor–acceptor complexes provide a useful platform for photocatalyst‐free radical generation under visible light irradiation and has emerged as a sustainable strategy for synthetic applications. Previous synthetic strategies based on EDA‐complex formations are typically based on engineering leaving groups into the substrates to suppress back electron transfer that impedes forward reaction. However, such pre‐functionalization affects efficiency and atom economy. This review highlights recent developments in the use of strategies for EDA‐complex formations to induce photochemical coupling‐ and cyclization reactions that do not rely on preinstalled sacrificial leaving‐groups. Most examples rely on alternative strategies to circumvent back electron transfer such as bond cleavage, oxygen‐mediated oxidation, or excitation of EDA complex precursors. These studies illustrate the rising promise of EDA complexes without incorporation of sacrificial leaving‐groups and highlight their potential as a broadly applicable, atom‐economical platform for photocatalyst‐free radical transformations in modern organic synthesis.

ABSTRACT The abrupt reorganization of the electronic configuration of spin‐crossover (SCO) compounds upon the transition from the low‐spin (LS) to the high‐spin (HS) state leads to significant changes in their structural, optical, and magnetic properties. As spin‐transitions can be triggered by a variety of external stimuli such as variations in temperature, pressure, or through light irradiation, these systems have attracted considerable attention for the design of multifunctional and stimuli‐responsive molecular materials. In this context, the synergistic coupling of SCO and luminescent properties holds great promise for the development of molecular spintronic devices capable of correlating the luminescence with an external perturbation, or of probing the magnetic state of the metal center through variations in emission intensity. This contribution provides a comprehensive overview of the field of luminescent SCO materials, with particular emphasis on systems that exhibit a genuine interplay between the two properties, both in materials and at the molecular level.

ABSTRACT The strategic generation of α‐fluoro radicals underpins powerful routes to fluorine‐rich architectures of high value in molecular design. Here, we disclose an operationally simple, catalyst‐free method for the photochemical activation of α‐halo fluorinated precursors using visible light and two inexpensive additives, sodium iodide and 2,6‐lutidine. This mild protocol enables in‐situ halide exchange and subsequent homolytic C–I bond scission to generate α‐fluoro radicals under ambient conditions. The generality of the platform is demonstrated across esters, sulphones, and nitriles, facilitating intermolecular coupling with alkenes, heteroarenes, and propellanes to access diverse fluorinated scaffolds. Mechanistic studies support the formation of a weak electron donor–acceptor complex that mediates bond activation, while the benign conditions permit merger with energy transfer catalysis for stereodivergent product formation.

ABSTRACT To celebrate the 125th anniversary of the Swiss Chemical Society, we present a review and perspective to highlight the recent research in breath analysis that has been conducted in Switzerland, with a particular focus on secondary electrospray ionization mass spectrometry (SESI‐HR‐MS). We focus on breath analysis research from 2019, the publication year of the last major review. We highlight where improvements are needed in experimental and clinical protocols and outline the current gaps in the field, to support the implementation of breath analysis into the clinical domain.

ABSTRACT C─H bond functionalization has appeared as one of the most efficient tools for building complex molecular scaffolds. Despite growing interest in remote C─H bond functionalization, achieving the distal site selectivity is highly challenging. Traditional “end‐on template” based methods usually require additional steps for installing and removing long directing templates, and often rely on expensive transition metals, which makes the process less sustainable. In this essay, an alternative concept known as “complementary catalysis” is discussed to achieve remote C─H arylation without the use of large templates. This approach requires a small directing group to control regioselectivity under mild conditions without any externally added ligands or activators. Most importantly, it paves a more sustainable route by improving the atom and step economy.