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Understanding the nonadiabatic dynamics of complex systems is a challenging task in computational photochemistry. Herein, we present an efficient and user-friendly quantum mechanics/molecular mechanics (QM/MM) interface to run on-the-fly nonadiabatic dynamics. Currently, this interface consists of an independent set of codes designed for general-purpose use. Herein, we demonstrate the ability and feasibility of the QM/MM interface by integrating it with our long-term developed JADE package. Tailored to handle nonadiabatic processes in various complex systems, especially condensed phases and protein environments, we delve into the theories, implementations, and applications of on-the-fly QM/MM nonadiabatic dynamics. The QM/MM approach is established within the framework of the additive QM/MM scheme, employing electrostatic embedding, link-atom inclusion, and charge-redistribution schemes to treat the QM/MM boundary. Trajectory surface-hopping dynamics are facilitated using the fewest switches algorithm, encompassing classical and quantum treatments for nuclear and electronic motions, respectively. Finally, we report simulations of nonadiabatic dynamics for two typical systems: azomethane in water and the retinal chromophore PSB3 in a protein environment. Our results not only illustrate the power of the QM/MM program but also reveal the important roles of environmental factors in nonadiabatic processes. [ABSTRACT FROM AUTHOR]

This study was focused on the photochemistry of OAlOH and three possible pathways, which were studied with high-level multireference configuration interaction ab initio calculations. We computed cuts of the six-dimensional potential energy surfaces for the ground, the lowest singlet and triplet excited states, and probed the photodissociation mechanisms and the stabilities. The OAlOH electronic spectrum, with an energy reaching 7.15 eV, contained four prominent peaks. Photodissociation to AlO, OH, and AlOH constituted a plausible mechanism within the deep-UV range (λ = 250.4 nm). Our data indicated the photostability of OAlOH in the near-UV‒Vis region, so detection with laser-induced fluorescence is possible. Fluorescence and phosphorescence may occur upon excitation at 363.5 nm. The roles of OAlOH in the photochemical reactions of Al-bearing molecules in the upper atmosphere and VY Canis Majoris are discussed. [ABSTRACT FROM AUTHOR]

Click chemistry refers to selective reactions developed for grafting of bio(macro)molecules in their biological media. Caged click compounds have been employed to spatiotemporally control click reactions. Here, we survey the uncaging of photo-dibenzocyclooctyne-OH (photoDIBO-OH) to its click-chemistry active form DIBO-OH, with particular attention to its conversion timescale and efficiency. Ultraviolet pump–infrared probe experiments reveal a stepwise decarbonylation: first, carbon monoxide (C≡O) is released within 1.8 ps, and then, it converts, within 10 ps, to DIBO-OH. Completion of uncaging is achieved with an efficiency of ∼50%. A successful demonstration of two-photon uncaging of photoDIBO-OH at long wavelength (700 nm) confers enhanced in vivo compatibility and proceeds on the same timescale. [ABSTRACT FROM AUTHOR]

We study the ultrafast time evolution of cyclobutanone excited to the singlet n → Rydberg state through non-adiabatic surface-hopping simulationsperformed at extended multi-state complete active space second-order perturbation (XMS-CASPT2) level of theory. These dynamics predict relaxation to the ground-state with a timescale of 822 ± 45 fs with minimal involvement of the triplets. The major relaxation path to the ground-state involves a three-state degeneracy region and leads to a variety of fragmented photoproducts. We simulate the resulting time-resolved electron-diffraction spectra, which track the relaxation of the excited state and the formation of various photoproducts in the ground state. [ABSTRACT FROM AUTHOR]

Owing to ring strain, cyclic ketones exhibit complex excited state dynamics with multiple competing photochemical channels active on the ultrafast timescale. While the excited state dynamics of cyclobutanone after π* ← n excitation into the lowest-energy excited singlet (S1) state has been extensively studied, the dynamics following 3s ← n excitation into the higher-lying singlet Rydberg (S2) state are less well understood. Herein, we employ fully quantum multiconfigurational time-dependent Hartree (MCTDH) simulations using a model Hamiltonian as well as "on-the-fly" trajectory-based surface-hopping dynamics (TSHD) simulations to study the relaxation dynamics of cyclobutanone following 3s ← n excitation and to predict the ultrafast electron diffraction scattering signature of these relaxation dynamics. Our MCTDH and TSHD simulations indicate that relaxation from the initially-populated singlet Rydberg (S2) state occurs on the timescale of a few hundreds of femtoseconds to a picosecond, consistent with the symmetry-forbidden nature of the state-to-state transition involved. There is no obvious involvement of excited triplet states within the timeframe of our simulations (<2 ps). After non-radiative relaxation to the electronic ground state (S0), vibrationally hot cyclobutanone has sufficient internal energy to form multiple fragmented products including C2H4 + CH2CO (C2; 20%) and C3H6 + CO (C3; 2.5%). We discuss the limitations of our MCTDH and TSHD simulations, how these may influence the excited state dynamics we observe, and—ultimately—the predictive power of the simulated experimental observable. [ABSTRACT FROM AUTHOR]

Phenylpropiolic acid (C6H5C≡CCOOH, PPA) isolated in nitrogen and xenon cryogenic matrices was studied by infrared spectroscopy. The experimental studies were complemented by a series of quantum chemical calculations carried out at the density functional theory (B3LYP) and MP2 levels of theory (with different basis sets). The calculations predicted the existence of two planar PPA conformers, differing in the arrangement of the carboxylic group. The higher-energy trans-PPA conformer has a negligible population in the gas phase at room temperature and was prepared in situ in the N2 cryomatrix through vibrationally-induced rotamerization of the lower-energy cis-PPA conformer, achieved using selective narrowband infrared excitation of the OH stretching coordinate of the latter species. Broadband UV (λ > 235 nm) irradiation of matrix-isolated cis-PPA was also undertaken, leading to the observation of cis-PPA → trans-PPA isomerization. No other UV-induced photoreactions were observed. The in situ generated trans-PPA conformer was found to decay back to cis-PPA in the dark by tunneling, and its lifetimes under different experimental conditions were determined. The assignment of the infrared spectra of both conformers is presented, considerably extending the vibrational information available on this molecule. [ABSTRACT FROM AUTHOR]

The UV photochemistry of small heteroaromatic molecules serves as a testbed for understanding fundamental photo-induced chemical transformations in moderately complex compounds, including isomerization, ring-opening, and molecular dissociation. Here, a combined experimental-theoretical study of 268 nm UV light-induced dynamics in 2-iodothiophene (C4H3IS) is performed. The dynamics are experimentally monitored with a femtosecond extreme ultraviolet (XUV) probe that measures iodine N-edge 4d core-to-valence transitions. Experiments are complemented by density functional theory calculations of both the pump-pulse induced valence excitations and the XUV probe-induced core-to-valence transitions. Possible intramolecular relaxation dynamics are investigated by ab initio molecular dynamics simulations. Gradual absorption changes up to ∼0.5 to 1 ps after excitation are observed for both the parent molecular species and emerging iodine fragments, with the latter appearing with a characteristic rise time of 160 ± 30 fs. Comparison of spectral intensities and energies with the calculations identifies an iodine dissociation pathway initiated by a predominant π → π* excitation. In contrast, initial excitation to a nearby n⟂ → σ* state appears unlikely based on a significantly smaller oscillator strength and the absence of any corresponding XUV absorption signatures. Excitation to the π → π* state is followed by contraction of the C–I bond, enabling a nonadiabatic transition to a dissociative π → σ C − I * state. For the subsequent fragmentation, a relatively narrow bond-length region along the C–I stretch coordinate between 230 and 280 pm is identified, where the transition between the parent molecule and the thienyl radical + iodine atom products becomes prominent in the XUV spectrum due to rapid localization of two singly occupied molecular orbitals on the two fragments. [ABSTRACT FROM AUTHOR]

In this work, we have studied the photodissociation of the protonated derivatives of N-nitrosodimethylamine [(CH3)2N–NO] with the CASPT2 method. It is found that only one of the four possible protonated species of the dialkylnitrosamine compound absorbs in the visible region at 453 nm, that is, N-nitrosoammonium ion [(CH3)2NH-NO]+. This species is also the only one whose first singlet excited state is dissociative to directly yield the aminium radical cation [(CH3)2NHN·]+ and nitric oxide. In addition, we have studied the intramolecular proton migration reaction {[(CH3)2N–NOH]+ → [(CH3)2NH–NO]+} both in the ground and excited state (ESIPT/GSIPT); our results indicate that this process is not accessible neither in the ground nor in the first excited state. Furthermore, as a first approximation, MP2/HF calculations on the nitrosamine–acid complex indicate that in acidic solutions of aprotic solvents, only [(CH3)2NH–NO]+ is formed. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Dynamic fluorescent materials play a crucial role in secure inks for data encryption; however, they are still plagued by issues such as photodegradation, poor latency, and susceptibility to unauthorized access. Herein, we propose a photochemically modulated dynamic fluorescent encryption system based on 1O2 sensitization of fluorescent composites, comprising a 1O2‐sensitive fluorophore (F2) and non‐emissive polymers. After UV irradiation, in‐situ generated 1O2 from the polymer effectively binds with F2 to form endoperoxides (F2EPO), resulting in a significant redshift in emission, up to 150 nm. The 1O2 concentration is closely related to the irradiation time, rendering different fluorescent colors in a time‐gated fashion. Moreover, the emission of F2EPO can be regulated by polymer chemical structure, molecular weight, and crosslinking density. Relying on these merits, we develop a dynamic data encryption method with various non‐emissive polymers as the data storage media, UV light irradiation as the data encoder, and F2 as the data decoder. UV light irradiation of diverse polymer solutions generates 1O2 at different concentrations, effectively encoding the data, which remains invisible under both UV and natural lights. The addition of F2 to these irradiated polymer solutions produces different redshifted fluorescence, enabling secure data decryption. Attributing to the non‐emissive nature of the polymers, time‐gated readout fashion, excellent latency of 1O2, and subtle interactions between 1O2 and F2, this data encryption is nearly undecipherable. This work offers an advantage data encryption approach beyond the reach of conventional fluorophores. [ABSTRACT FROM AUTHOR]

This document explores the use of ligand-to-metal charge transfer (LMCT) catalysis with base metals, such as nickel, cobalt, and copper, in organic transformations. The authors discuss recent advancements in the field and the potential for expanding the synthetic repertoire of this strategy. They emphasize the importance of refining ligands to promote organometallic mechanisms and further developing photoinduced LMCT for sustainable synthetic methods. The document includes contributions from researchers Sean M. Treacy and Tomislav Rovis, who have made significant contributions to the field. [Extracted from the article]

N‐phenyl dibenzothiophene sulfoximine has been demonstrated to produce phenyl nitrene and dibenzothiophene S‐oxide upon irradiation with UV‐A light, and dibenzothiophene S‐oxide upon further irradiation releases triplet atomic oxygen. Thus, N‐phenyl dibenzothiophene sulfoximine exhibits a rare dual‐release capability in its photochemistry. In this work, N‐substituted dibenzothiophene sulfoximine derivatives are irradiated with UV‐A light to compare their photochemistry and quantum yield of dibenzothiophene S‐oxide production with that of N‐phenyl dibenzothiophene sulfoximine. Both N‐aryl and N‐alkyl derivatives of dibenzothiophene sulfoximine are examined to observe their effects on the quantum yield of the photolysis reaction. Adding electron withdrawing N‐aryl substituents is shown to increase the quantum yield of dibenzothiophene S‐oxide production, while adding electron donating N‐aryl substituents is shown to decrease the quantum yield. The quantum yield was slightly lowered or not increased by most N‐alkyl substituents. Furthermore, the quantum yield was not augmented by branching and steric hindrance effects associated with the N‐alkyl substituents. These results suggest that electronic modulation of the sulfoximine bonds affects the observed photolysis reaction. [ABSTRACT FROM AUTHOR]

Comprehensive Summary Traditional reduction coupling reactions of two bromides typically rely on transition metal catalysis. Here, we introduce the development of a visible‐light catalytic direct reduction coupling reaction between α‐CF3‐alkyl bromides and alkynyl bromides to access valuable organic frameworks. Our research confirms the excellent compatibility of this reaction with various functional groups, which could be used to modify the substrate with biologically active molecular fragments. Mechanistic investigations, including control experiments, fluorescence quenching studies, and light‐switching experiments, have provided insights into the reaction mechanism. This study paves the way for the application of visible‐light catalysis in diverse synthetic transformations, offering a sustainable and efficient approach to organic synthesis. [ABSTRACT FROM AUTHOR]

Ten novel 4-esterchalcones, licochalcone analogues, were strategically synthesized to study the effect of electro-donating or electro-withdrawing substituents in the aryl enone moiety on their pharmacological and photoprotective properties. 4-Esterchalcones had their drug-like character evaluated, which demonstrated positive characteristics for the development of novel drug candidates. In the in vitro antimicrobial evaluation, isovaleryl 4-esterchalcones showed activity against strains of Staphylococcus aureus, Candida albicans and C. tropicalis with minimum inhibitory concentration (MIC) in the range of 2.64-3.32 µmol mL−1, and the isobutyryl 4-esterchalcone 5d (4'-Br) presented antimicrobial activity against all strains tested, with a MIC of 2.74 µmol mL−1. In the UV-Vis study, λmax were observed at 312-327 nm, the UVB range, mainly. The best SPF-UVB results ranged from 18.04 to 21.06, with high εmax values, indicating that 4-esterchalcones have the potential to act as sunscreens. Furthermore, along with the environmental concern, halogenated compounds demonstrated slightly toxic on Artemia salina. [ABSTRACT FROM AUTHOR]

Aminocatalysis is a well‐established tool that enables the production of enantioenriched compounds under mild conditions. Its versatility is underscored by its seamless integration with various synthetic approaches. While the combination of aminocatalysis with metal catalysis, photochemistry, and stoichiometric oxidants has been extensively explored, its synergy with electrochemical activation remains largely unexplored. Herein, we present the successful merger of electrochemistry and aminocatalysis to perform SOMO‐type transformations, expanding the toolkit for asymmetric electrochemical synthesis. The methodology harnesses electricity to drive the oxidation of catalytically generated enamines, which ultimately partake in enantioselective radical processes, leading to α‐alkylated aldehydes. Crucially, mechanistic studies highlight how this electrochemical strategy is enabled by the use of a redox shuttle, 4,4′‐dimethoxybiphenyl, to prevent catalyst degradation and furnishing the coveted compounds in good yield and high enantioselectivity. [ABSTRACT FROM AUTHOR]

Aminocatalysis is a well‐established tool that enables the production of enantioenriched compounds under mild conditions. Its versatility is underscored by its seamless integration with various synthetic approaches. While the combination of aminocatalysis with metal catalysis, photochemistry, and stoichiometric oxidants has been extensively explored, its synergy with electrochemical activation remains largely unexplored. Herein, we present the successful merger of electrochemistry and aminocatalysis to perform SOMO‐type transformations, expanding the toolkit for asymmetric electrochemical synthesis. The methodology harnesses electricity to drive the oxidation of catalytically generated enamines, which ultimately partake in enantioselective radical processes, leading to α‐alkylated aldehydes. Crucially, mechanistic studies highlight how this electrochemical strategy is enabled by the use of a redox shuttle, 4,4′‐dimethoxybiphenyl, to prevent catalyst degradation and furnishing the coveted compounds in good yield and high enantioselectivity. [ABSTRACT FROM AUTHOR]

Transition metal‐catalyzed C−H arylation polymerization (CHAP) is an attractive tool for constructing π‐conjugated polymers in a sustainable manner. However, the existing methods primarily rely on palladium catalysis, which usually entails harsh reaction conditions and branching/cross‐linking. Here we report the first example of an ambient‐temperature ruthenium‐catalyzed C−H arylation polymerization induced by visible light irradiation. The present polymerization can produce various meta‐ and para‐linked polymers in excellent yields with high molecular weights. The remarkable feature of our mild reaction platform is represented by high chemoselectivity, leading to polymers that are otherwise inaccessible under conventional reaction conditions at high temperatures. [ABSTRACT FROM AUTHOR]

This study presents a thorough spectroscopic analysis of TiO2-Pt systems under LED irradiation, with a focus on elucidating the photodeposition process of Pt nanoparticles onto TiO2 surfaces. The methodology leverages an innovative LED photoreactor tailored to a specific spectral range, enabling precise characterization of the excitation spectrum of TiO2-Pt composites. Through the identification of Pt precursor species and their excitation under LED-UV light, a photodeposition mechanism is proposed involving concurrent excitation of both the TiO2 semiconductor and the H2PtCl6 precursor. The LED photoreactors are employed to scrutinize the excitation profile of TiO2-Pt materials, revealing that the incorporation of Pt nanoparticles does not expand TiO2's absorption spectrum. Furthermore, UV-A exposure in the absence of Pt did not induce the formation of surface defects, underscoring the lack of visible light activity in TiO2-Pt systems. Spectroscopic analyses, complemented by naproxen photooxidation experiments, indicate the absence of a significant plasmonic effect in Pt nanoparticles within the experimental framework. Mass spectroscopy results corroborate the presence of distinct naproxen degradation pathways, suggesting minimal influence from photocatalyst properties. This research provides a detailed spectroscopic insight into TiO2-Pt photocatalysis, enriching the knowledge of photocatalytic materials in LED lighting. [ABSTRACT FROM AUTHOR]

o-Carborane is an icosahedral cluster containing boron and has been paid attention as a versatile platform for constructing stimuli-responsive materials with solid-state luminescence properties by suppressing aggregation-caused quenching (ACQ), which is the emission annihilation process observed in condensed states, such as concentrated solutions, solids and films. Non-specific intermolecular interactions in the condensed states resulting in ACQ are disturbed by the spherical boron cluster. More recently, it has been demonstrated from several reports that o-carborane is capable of assisting solid-state excimer emission in aryl-modified o-carboranes. Moreover, some of these materials provide unique stimuli-responsiveness. In the commodity design for solid-state luminescent materials, o-carboranes are responsible for disturbing intermolecular interactions and subsequently presenting solid-state luminescence. On the other hand, excimer emission, which is inducible from the intermolecular photophysical process, has been discovered in the solid state based on o-carborane materials. In this manuscript, recent progress in stimuli-responsive luminescent materials via excimer formation will be described. Moreover, as the further potential of o-carborane materials, recent findings on the photo-salient effect which can be induced through excimer formation followed by photoreaction will also be explained. [ABSTRACT FROM AUTHOR]

A photochemical synthesis of biologically relevant benzyl oxindoles is presented via electron‐donor acceptor (EDA) complex strategy. This exogenous photocatalyst‐free method describes the formation of a new electron donor‐acceptor complex based on potassium carbonate and thianthrenium salts for C(sp2)−C(sp3) bond formation. This transition‐metal free reaction allows a rapid increase in oxindoles molecular complexity chemical space, tolerating different functional groups as well as sophisticated biomolecules. The scalability and sustainability of this method is highlighted by an important waste recovery protocol. Mechanistic investigations support the formation of an EDA complex that induces a radical chain, and the applicability of this method is showcased by straightforward derivatization reactions. [ABSTRACT FROM AUTHOR]

This Concept outlines cutting‐edge progress in catalytic and enantioselective radical reactions facilitated by redox‐active chiral Lewis acids upon visible light excitation. These catalytic systems exploit the high reactivity of radical species to enable efficient stereocontrolled radical recombination. We delve into the design, underlying mechanisms, and practical applications of these catalysts, aiming for precise stereocontrolled bond formation. The synergistic blend of chirality and reactivity has brought a new level of precision to enantioselective radical additions, reshaping the approach to asymmetric synthesis. This Concept focuses on the recent progress and effective application of redox‐active chiral Lewis acids, including Rh, Ir, Ga and Ni, in catalyzing enantioselective radical reactions, which offers a comprehensive perspective on modern methods and projecting future directions in enantioselective radical chemistry. [ABSTRACT FROM AUTHOR]

Visible‐light‐activated organic reactions unlock novel avenues for complex molecular transformations, impossible under standard "thermal" conditions, which makes them powerful tools in the arsenal of synthetic chemistry. However, transition metal‐based or organic photoredox catalysts are often used to ensure productive absorption of visible light, which might be not desirable to medicinal chemistry and industry due to toxicity, low sustainability, and high cost of most photocatalysts. A more environmentally and economically benign approach is based on the formation of transient electron donor‐acceptor (EDA) complexes between two reagents or a reagent and an additive, that readily absorb visible light, acting as internal photosensitizers. Within the EDA complex‐based arylation strategies, chemical transformations are mediated by noncovalent interaction between two molecules, namely between electron‐poor aryl halides or their synthetic equivalents and electron‐rich nucleophilic reagents or additives. Moreover, besides stoichiometric EDA complexes between two molecules, EDA complex based organocatalysis can be achieved in certain cases through regeneration of the donor molecules in the course of the reaction. Photoexcitation of the EDA complexes induces a single electron transfer (SET) process to generate aryl radical species for the arylation step. This Review will focus on the state‐of‐the‐art EDA complex‐based arylation strategies utilizing aryl halides, aryldiazonium, diaryliodonium, arylsulfonium and arylphosphonium salts as reactants, published mainly in the last five years. [ABSTRACT FROM AUTHOR]

Small carbo‐ and heterocyclic ring systems have experienced a significant increase in importance in recent years due to their relevance in modern pharmaceuticals, as building blocks for designer materials or as synthetic intermediates. This necessitated the development of new synthetic methods for the preparation of these strained ring systems focusing on effectiveness and scalability. The high ring strain of these entities as well as the use of high‐energy reagents and intermediates has often challenged their synthesis. Continuous flow approaches have thus emerged as highly effective means to safely and reliably access these strained scaffolds. In this short review, key developments in this field are summarised showcasing the power of continuous flow approaches for accessing 3‐ and 4‐membered ring systems via thermal, photo‐ and electrochemical processes. [ABSTRACT FROM AUTHOR]

This article discusses a study on the chemoselective reduction of barbiturates using photochemically excited flavin catalysts. The researchers explored the use of samarium(II) iodide and reduced flavins as reductants for barbiturates with multiple carbonyl groups. They found that flavin-mediated reduction led to the formation of alicyclic hemiaminals, providing a new method for reductive cyclizations. The study also compared flavin catalysis to the well-established SmI2 reductant and found that flavin catalysis proceeds differently, making it useful for various transformations that require reductive activation of carbonyl functional groups. [Extracted from the article]

This article discusses recent advancements in oxidative cleavage reactions, specifically focusing on alternative methods to the traditional ozonolysis process. The article highlights two main approaches: aerobic cleavage using visible light excitation with molecular oxygen, and anaerobic cleavage using photoexcited nitroarenes. Both methods offer advantages such as improved reaction efficiency, cost economy, and expanded substrate scope. However, challenges still exist, such as the formation of overoxidation products and the requirement for stoichiometric amounts of nitroarenes. Overall, these methods provide a foundation for the development of sustainable oxidative cleavage reactions. [Extracted from the article]

This article explores the use of N-heterocyclic carbenes (NHCs) in photochemical and electrochemical catalysis for organic synthesis. NHCs have unique catalytic properties and are cost-effective and environmentally friendly. The article discusses various reactions mediated by NHCs, including the formation of C-O and C-N bonds. It also highlights the combination of NHC catalysis with photoredox catalysis for radical reactions, such as alkylation and benzylation of alkenes. The article emphasizes the potential of NHC and photoredox catalysis in enabling the construction of diverse organic compounds under mild conditions. Additionally, it presents examples of NHC-mediated reactions and discusses future research opportunities in this field. [Extracted from the article]

Development of high‐performance photoinitiator is the key to enhance the printing speed, structure resolution and product quality in 3D laser printing. Here, to improve the printing efficiency of 3D laser nanoprinting, we investigate the underlying photochemistry of gold and silver nanocluster initiators under multiphoton laser excitation. Experimental results and DFT calculations reveal the high cleavage probability of the surface S−C bonds in gold and silver nanoclusters which generate multiple radicals. Based on this understanding, we design several alkyl‐thiolated gold nanoclusters and achieve a more than two‐orders‐of‐magnitude enhancement of photoinitiation activity, as well as a significant improvement in printing resolution and fabrication window. Overall, this work for the first time unveils the detailed radical formation pathways of gold and silver nanoclusters under multiphoton activation and substantially improves their photoinitiation sensitivity via surface engineering, which pushes the limit of the printing efficiency of 3D laser lithography. [ABSTRACT FROM AUTHOR]

1,2,4‐triazolo‐[4,3‐a]pyrazine was prepared via a two‐step electrochemical, photochemical process. First, a 5‐substituted tetrazole is electrochemically coupled to 2,6‐dimethoxypyrazine to yield 1,5‐ and 2,5‐ disubstituted tetrazoles. Subsequent photochemical excitation of the 2,5‐disubstituted tetrazole species using an ultraviolet lamp releases nitrogen gas and produces a short‐lived nitrilimine intermediate. Subsequent cyclization of the nitrilimine intermediate yields a 1,2,4‐triazolo‐[4,3‐a]pyrazine backbone. The scope of this reaction was explored using various tetrazoles and pyrazines. Materials produced were identified using chemical analytical techniques and computationally studied for potential application as an insensitive energetic material. [ABSTRACT FROM AUTHOR]

Development of high‐performance photoinitiator is the key to enhance the printing speed, structure resolution and product quality in 3D laser printing. Here, to improve the printing efficiency of 3D laser nanoprinting, we investigate the underlying photochemistry of gold and silver nanocluster initiators under multiphoton laser excitation. Experimental results and DFT calculations reveal the high cleavage probability of the surface S−C bonds in gold and silver nanoclusters which generate multiple radicals. Based on this understanding, we design several alkyl‐thiolated gold nanoclusters and achieve a more than two‐orders‐of‐magnitude enhancement of photoinitiation activity, as well as a significant improvement in printing resolution and fabrication window. Overall, this work for the first time unveils the detailed radical formation pathways of gold and silver nanoclusters under multiphoton activation and substantially improves their photoinitiation sensitivity via surface engineering, which pushes the limit of the printing efficiency of 3D laser lithography. [ABSTRACT FROM AUTHOR]

The design of new and more sustainable synthetic protocols to access new materials or valuable compounds will have a high impact on the broader chemistry community. In this sense, continuous‐flow photochemistry has emerged as a powerful technique which has been employed successfully in various areas such as biopharma, organic chemistry, as well as materials science. However, it is important to note that chemical processes must not only advance towards new or improved chemical transformations, but also implement new technologies that enable new process opportunities. For this reason, the design of novel photoreactors is key to advancing photochemical strategies. In this sense, the use of equipment and techniques embracing processes intensification is important in developing more sustainable protocols. Among the most recent applications, spinning continuous flow reactors, such as rotor reactors or vortex reactors, have shown promising performance as new synthetic tools. Nevertheless, there is currently no review in the literature that effectively summarizes and showcases the most recent applications of such type of photoreactors. Herein, we highlight fundamental aspects and applications of two categories of spinning reactors, the Spinning Disc Reactors (SDRs) and Thin Film Vortex reactors, critiquing the scope and limitations of these advanced processing technologies. Further, we take a view on the future of spinning reactors in flow as a synthetic toolbox to explore new photochemical transformations. [ABSTRACT FROM AUTHOR]

The photochemical cyclodehydrochlorination (CDHC) reaction has recently been used to prepare a wide variety of polycyclic aromatic hydrocarbons and graphene nanoribbons (GNRs). However, the parameters affecting the efficiency of this reaction have been scarcely studied. In this work, we investigated how the reaction conditions influence the outcome of the reaction. The effect of functional groups on the different phenyl rings of the o‐terphenyl scaffold was also studied. The reaction kinetics follow the same trend as Hammett's constant when electron‐donating and electron‐withdrawing groups are present on the ring bearing the chlorine. The CDHC reaction can be successfully performed using less energetic 365 nm light in the presence of a triplet sensitizer. Computational results provide insight on the reaction mechanism, notably by identifying its three intermediate structures as well as its limiting step. [ABSTRACT FROM AUTHOR]

Terrestrial planets currently in the habitable zone around M dwarfs are estimated to have been in runaway greenhouse conditions for up to ∼1 Gyr due to the long-term pre-main-sequence phase of M dwarfs. These planets likely lose a significant portion of water during the pre-main-sequence phase owing to H2O photolysis followed by hydrogen and oxygen loss to space. However, the effects of H2O reproduction reactions and UV shielding by chemical products that reduce photolysis-induced water loss have yet to be estimated. Here, we apply a 1D photochemical model to a H2O-dominated atmosphere of an Earth-like planet around a pre-main-sequence M dwarf to estimate these effects. We find that water loss is suppressed by efficient H2O reproduction reactions and by UV shielding due to O2. The water loss rate decreases by several to several hundred times compared to that in previous studies, with the assumption that the water loss rate is limited by stellar X-ray and extreme-ultraviolet flux or hydrogen diffusion through the atmosphere. Our results imply that terrestrial planets currently in the habitable zone around M dwarfs are more likely to retain surface water than previously estimated. [ABSTRACT FROM AUTHOR]

Using High‐Throughput Experimentation (HTE), a visible light‐mediated etherification method was developed, employing the organic photocatalyst thioxanthen‐9‐one (TXO) and a commercially available, air‐stable nickel source. Design of Experiments (DoE) techniques were utilized in conjunction with HTE to identify optimal reaction conditions which are mild, cost‐effective, robust and therefore suitable for use in an industrial setting. A diverse substrate scope was prepared via parallel synthesis and selected examples were demonstrated on a 4.2 mmol scale in batch. Furthermore, the reaction was successfully performed on an 83 mmol scale, utilizing a standard jacketed reactor and Kessil PR160 L lamps. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A visible‐light‐enabled, photocatalyst‐free hydroacylation reaction of azodicarboxylic acid derivatives was described. This radical conjugate addition (RCA) protocol relied on the dual role of 4‐acyl‐1,4‐dihydropyridine (acyl‐DHP) reagents that besides being as radical reservoirs, they also enabled the conversion of radical adducts to anion intermediates via reduction. Under "catalyst‐oxidant‐additive free" conditions, a wide range of structurally different acyl hydrazide products were readily obtained in 56%—99% yields. The utility of this transformation was further demonstrated by the scale‐up synthesis and downstream derivatization. [ABSTRACT FROM AUTHOR]

Urea is believed to have been essential to the synthesis of prebiotic nucleotides and thereby the RNA or DNA of the first lifeforms. Models suggesting that life began in wet‐dry cycles around shallow aquatic ponds imply that reactants such as urea were exposed to deep ultraviolet irradiation from the young sun. Detrimental photodissociation of urea induced by deep UV excitation potentially challenges these models. We here follow the primary deep ultraviolet photochemistry of aqueous urea. The data show that urea is barely excited at 200 nm due to weak ultraviolet absorption. The likelihood of photodissociation is further reduced by strong intra‐molecular coupling of the CN and CO stretch vibrations accompanied by an efficient dissipation of the excitation energy to the surrounding water molecules mitigated by urea‐water hydrogen bonds. We find that 54±5 % of the excited urea molecules dissociate. Reactions between the photoproducts and surrounding solvent molecules form carbamic acid or the carbamate anions within 0.6 ps. The molecules that do not dissociate return to the electronic ground state in 2 ps. Interestingly, the photodissociation processes of urea in the aqueous phase is different from earlier reported reactions observed following the VUV photolysis of urea in noble gas matrices and highlight the potential influence of water on the prebiotic photochemistry. [ABSTRACT FROM AUTHOR]

A novel class of diazonium salts is introduced for the photochemical aryl‐aryl coupling to produce (substituted) biphenyls. As common diazonium tetrafluoroborate salts fail, soluble and safe aryl diazonium trifluoroacetates are applied. In this mild synthesis route no catalysts are required to generate an aryl‐radical by irradiation with UV‐A light (365 nm). This reactive species undergoes direct C−H arylation at an arene, forming the product in reasonable reaction times. With the implementation of a continuous flow setup in a capillary photoreactor 13 different biphenyl derivatives are successfully synthesized. By integrating an inline 19F‐NMR benchtop spectrometer, samples are reliably quantified as the fluorine‐substituents act as a probe. Here, real‐time NMR spectroscopy is a perfect tool to monitor the continuously operated system, which produces fine chemicals of industrial relevance even in a multigram scale. [ABSTRACT FROM AUTHOR]

An organophotoelectrocatalytic method for the C(sp2)–H alkylation of heteroarenes with unactivated C(sp3)–H compounds through dehydrogenation cross-coupling has been developed. The C(sp2)–H alkylation combines organic catalysis, photochemistry and electrochemistry, avoiding the need for external metal-reagents, HAT-reagents, and oxidants. This protocol exhibits good substrate tolerance and functional group compatibility, providing a straightforward and powerful pathway to access a variety of alkylated heteroarenes under green conditions. [ABSTRACT FROM AUTHOR]

Photoclick reactions combine the advantages offered by light‐driven processes and classical click chemistry and have found applications ranging from surface functionalization, polymer conjugation, photo‐crosslinking, and protein labeling. Despite these advances, the dependency of most of the photoclick reactions on UV light poses a severe obstacle for their general implementation, as this light can be absorbed by other molecules in the system resulting in their degradation or unwanted reactivity. However, the development of a simple and efficient system to achieve bathochromically shifted photoclick transformations remains challenging. Here, we introduce triplet‐triplet energy transfer as a fast and selective way to enable visible light‐induced photoclick reactions. Specifically, we show that 9,10‐phenanthrenequinones (PQs) can efficiently react with electron‐rich alkenes (ERAs) in the presence of a catalytic amount (as little as 5 mol %) of photosensitizers. The photocycloaddition reaction can be achieved under green (530 nm) or orange (590 nm) light irradiation, representing a bathochromic shift of over 100 nm as compared to the classical PQ‐ERAs system. Furthermore, by combining appropriate reactants, we establish an orthogonal, blue and green light‐induced photoclick reaction system in which the product distribution can be precisely controlled by the choice of the color of light. [ABSTRACT FROM AUTHOR]

Photoclick reactions combine the advantages offered by light‐driven processes and classical click chemistry and have found applications ranging from surface functionalization, polymer conjugation, photo‐crosslinking, and protein labeling. Despite these advances, the dependency of most of the photoclick reactions on UV light poses a severe obstacle for their general implementation, as this light can be absorbed by other molecules in the system resulting in their degradation or unwanted reactivity. However, the development of a simple and efficient system to achieve bathochromically shifted photoclick transformations remains challenging. Here, we introduce triplet‐triplet energy transfer as a fast and selective way to enable visible light‐induced photoclick reactions. Specifically, we show that 9,10‐phenanthrenequinones (PQs) can efficiently react with electron‐rich alkenes (ERAs) in the presence of a catalytic amount (as little as 5 mol %) of photosensitizers. The photocycloaddition reaction can be achieved under green (530 nm) or orange (590 nm) light irradiation, representing a bathochromic shift of over 100 nm as compared to the classical PQ‐ERAs system. Furthermore, by combining appropriate reactants, we establish an orthogonal, blue and green light‐induced photoclick reaction system in which the product distribution can be precisely controlled by the choice of the color of light. [ABSTRACT FROM AUTHOR]

Styrylbenzazoles form a promising yet under‐represented class of photoswitches that can perform a light‐driven E‐Z isomerization of the central alkene double bond without undergoing irreversible photocyclization, typical of the parent stilbene. In this work, we report the synthesis and photochemical study of 23 styrylbenzazole photoswitches. Their thermal stabilities, quantum yields, maximum absorption wavelengths and photostationary state (PSS) distributions can be tuned by changing the benzazole heterocycle and the substitution pattern on the aryl ring. In particular, we found that push‐pull systems show large redshifts of the maximum absorption wavelengths and the highest quantum yields, whereas ortho‐substituted styrylbenzazole photoswitches exhibit the most favorable PSS ratios. Taking advantage of both design principles, we produced 2,6‐dimethyl‐4‐(dimethylamino)‐styrylbenzothiazole, a thermally stable and efficient P‐type photoswitch which displays negative photochromism upon irradiation with visible light up to 470 nm to obtain a near‐quantitative isomerization with a very high quantum yield of 59 %. Furthermore, 4‐hydroxystyrylbenzoxazole was demonstrated to be a pH‐sensitive switch which exhibits a 100 nm redshift upon deprotonation. Ortho‐methylation of its benzothiazole analogue improved the obtained PSS ratio in its deprotonated state from E : Z=53 : 47 to E : Z=18 : 82. We anticipate that this relatively unexplored class of photoswitches will form a valuable expansion of the current family of photoswitches. [ABSTRACT FROM AUTHOR]

The cyclopropanation reaction of alkenes with photolytically‐generated chlorocarbenes from chlorodiazirines is reported as an effective way to prepare substituted 3‐chloro‐3‐aryl‐cyclopropanes. This practical and efficient approach allows the synthesis of various 3‐chloro‐3‐aryl‐cyclopropanes (32 examples) in continuous flow in 5‐minute residence time under light‐emitting diode (LED) irradiation. The conditions using 380 nm LED irradiation were successfully extended to the synthesis of substituted 3‐bromo‐3‐aryl‐cyclopropanes (3 examples). [ABSTRACT FROM AUTHOR]

We report a mechanistic investigation of an aromatic dithioimide (2SS) displaying puzzling yet efficient photochemistry in ether solvents. Perplexingly, 2SS dissolved in ether solvents in a sealed and degassed vial was photochemically converted to the corresponding diimide (2OO), as determined by 1H NMR following product extraction. With no external sources of oxygen in the sample, could the oxygen in 2OO be from the ether itself? To study this unprecedented proposition, we attempt to uncover the ether's involvement in this reaction. As seen by laser‐flash photolysis, 2SS appears to first react with the solvent from its singlet excited state. Following the reaction by NMR under rigorously oxygen‐ and water‐free conditions led to the identification of a photoreductive pathway that quantitatively transformed one thione into a methylene to yield 2SH2. Subsequent oxidation of 2SH2 or irradiation of 2SS under air proved that molecular oxygen was indeed necessary to observe an oxidative pathway leading to 2OO, ruling out the initially proposed involvement of an ether oxygen. An explanation of 2SS desulfurization was further revealed through the study of solvent by‐products by GC‐MS analysis. Supported by DFT calculations, a mechanism is proposed to involve a chain reaction initiated by photochemically generated ether radical. [ABSTRACT FROM AUTHOR]

The ability to study chemical dynamics on ultrafast timescales has greatly advanced with the introduction of X-ray free electron lasers (XFELs) providing short pulses of intense X-rays tailored to probe atomic structure and electronic configuration. Fully exploiting the full potential of XFELs requires specialized experimental endstations along with the development of techniques and methods to successfully carry out experiments. The liquid jet endstation (LJE) at the Linac Coherent Light Source (LCLS) has been developed to study photochemistry and biochemistry in solution systems using a combination of X-ray solution scattering (XSS), X-ray absorption spectroscopy (XAS), and X-ray emission spectroscopy (XES). The pump–probe setup utilizes an optical laser to excite the sample, which is subsequently probed by a hard X-ray pulse to resolve structural and electronic dynamics at their intrinsic femtosecond timescales. The LJE ensures reliable sample delivery to the X-ray interaction point via various liquid jets, enabling rapid replenishment of thin samples with millimolar concentrations and low sample volumes at the 120 Hz repetition rate of the LCLS beam. This paper provides a detailed description of the LJE design and of the techniques it enables, with an emphasis on the diagnostics required for real-time monitoring of the liquid jet and on the spatiotemporal overlap methods used to optimize the signal. Additionally, various scientific examples are discussed, highlighting the versatility of the LJE. [ABSTRACT FROM AUTHOR]

Vivianite is a hydrous Fe(II) phosphate mineral found in anoxic environments that plays an integral role in P cycling and environmental biogeochemistry. Imbued in the vivianite literature dating as far back as 1918 is the notion that vivianite is light-sensitive and susceptible to rapid photooxidation induced entirely by solar light. However, despite an exhaustive search, to our knowledge this conventionally accepted assumption has never been directly tested, nor has the band gap ever been measured. Resolving this question of photochemical control of vivianite redox chemistry is important for performing and interpreting experiments involving vivianite reactivity with contaminants, and potentially iron and phosphate cycling in the photic zone of aquatic systems. The present study was specifically designed to address this question. Pure synthetic vivianite samples were irradiated in aqueous suspensions with a Xe lamp at conditions mimicking the solar spectrum and compared to dark controls. Particles stirred in anoxic suspensions for up to 66 days showed no detectable oxidation irrespective of light exposure, according to colorimetric Fe(II)/Fe(III) assays, micro X-ray diffraction, and Raman spectroscopy. In contrast, the same experiment performed using air-equilibrated suspensions showed systematic oxidation of up to ∼80 mol% Fe(II) at 66 days, but again with no detectable light exposure effect. To test for UV reactivity, further experiments on vivianite powders under air versus N 2 atmosphere were performed using a Hg lamp with a longpass filter. In contrast to oxidation in air where no effect of light was detected, after 24 h irradiation anoxically, an additional 0.8 % Fe was oxidized compared to dark controls, and after 13 days only an additional 0.3 % Fe was oxidized. The band gap of pure vivianite was measured by the Tauc method to be 3.5 eV. Contrary to previous reports, solar light has minimal impact on the oxidation of pure vivianite; any such effect would be insignificant when compared to its relatively fast oxidation by oxygen exposure. As such, light does not need to be excluded when running typical vivianite laboratory experiments. Long-term storage of natural vivianite in museums or private collections should continue protective measures given that a possible photocatalytic role of impurities cannot yet be ruled out. Nonetheless, at all depths in natural aquatic systems, including the photic zone, it appears that the primary abiotic control on the reactivity and half-life of vivianite particles would be the dissolved oxygen concentration, not light exposure. [ABSTRACT FROM AUTHOR]

Comprehensive Summary In this paper, the difunctionalizative perfluoroalkyloximation of alkenes has been developed for the first time. This photochemical method allows for the synthesis of various perfluoroalkyl ethanone oximes with excellent regioselectivity and good functional group tolerance. Our method employs the most common perfluoroalkyl source, perfluoroalkyl iodides, as Rf reagents. Besides long‐chain perfluoroalkyl groups, this approach could be extended to incorporating additional groups, including trifluoromethyl, difluoromethyl, sulfonyl, and malonate, selectively into olefins, resulting in a range of β‐substituted ethanone oximes. Notably, the potential of this method in the Fukuyama indole synthesis, generating novel 2‐perfluoroalkylated 3‐(α‐oximidobenzyl)indoles via a radical cascade mechanism with 2‐vinylphenylacryloyl isocyanate as the radical acceptor, presents a compelling avenue for drug synthesis. The protocol is efficient, scalable, and useful for late‐stage modification of bioactive molecules. [ABSTRACT FROM AUTHOR]

Comprehensive Summary Unsymmetrical diarylamines are crucial components in many pharmaceuticals and functional materials. In this study, we introduce an efficient Chan‐Lam cross‐coupling method that utilizes phenylboronic acids and aryl azides as coupling agents in a redox‐neutral environment, enabled by a synergistic nickel/photoredox catalytic system. This approach leverages a proton‐coupled electron transfer mechanism to bypass the typical nitrene pathway associated with aryl azides, which is prone to intramolecular rearrangement, C—H amination, and reductive hydrogenation. Notably, our method exhibits broad compatibility with a variety of functional groups, including those derived from pharmaceuticals, demonstrating its versatile potential in organic synthesis and drug modification. [ABSTRACT FROM AUTHOR]

This article explores the use of light-controlled catalysis triggered by ligand photodissociation from cobalt complexes. The researchers developed a method that allows for the switching between two different reaction outcomes based on the presence or absence of visible light. They demonstrated this approach in hydroboration reactions and achieved selective catalysis for 1,2- or 1,4-addition depending on the reaction conditions. The researchers also investigated the mechanism behind these reactions and used the method to access enolborates and syn-aldol products. This research has the potential to expand the possibilities for catalytic reactions and could lead to further advancements in the field. [Extracted from the article]

The regioselective synthesis of biphenyls, which are economically important pharmaceuticals, agrochemicals, and liquid crystals, is a challenging task. Current methods rely on metal‐dependent cross‐coupling reactions, which unfortunately require the use of harmful halogenated aryls and heavy metal catalysts that are toxic and difficult to remove from the final products. Recently, we have circumvented these problems by developing a metal‐free and broadly applicable photochemical method for biphenyl synthesis using UV−C light, called photosplicing. Here we present an improved method using photosensitizers in combination with UV−B, UV−A light, or sunlight. Using a high‐precision flow reactor with deep‐UV LEDs, we investigated the ability of commonly available organic photosensitizers to enhance the photosplicing reaction and identified a number of suitable photosensitizers with the required triplet energy. This method allows for easy batch synthesis of biaryls in borosilicate glassware and paves the way for their large‐scale production without the need for flow reactors. [ABSTRACT FROM AUTHOR]

Aryl diazonium salts are versatile compounds known for their reactivity in various transformations. In this study, we explored the arylation of 3‐methylene isoindolinones using aryl diazonium salts. The objective was to develop a method for accessing 3‐benzyl‐3‐methoxyisoindolin‐1‐ones, a class of compounds with diverse biological activities and synthetic importance. Optimization of the reaction conditions revealed the significance of light irradiation for improved yields. The substrate scope investigation demonstrated the compatibility of various diazonium salts and N‐substituents on the 3‐methylene isoindolinone scaffold, yielding the corresponding methoxy lactams with high yields. Mechanistic insights were obtained by observing the effect of base and light irradiation. Two initiation mechanisms were proposed: in the presence of a base, the reaction could proceed even without light irradiation, while light irradiation was necessary in the absence of a base. DFT calculations were performed to elucidate the mechanism of the reaction and provide energetic considerations [ABSTRACT FROM AUTHOR]

The chemistry of light dipnictenes has been widely investigated in the last century with remarkable achievements especially for azobenzene derivatives. In contrast, distibenes and dibismuthenes are relatively rare and show very limited reactivity. Herein, we have designed a protocol using visible light to enhance the reactivity of heavy dipnictenes. Exploiting the distinctive π–π* transition, we have been able to isolate unique examples of dipnictene‐cobalt complexes. The reactivity of the distibene complex was further exploited using red light in the presence of a diazoolefin to access an unusual four‐membered bicyclo[1.1.0]butane analog, containing only a single carbon atom. These findings set the bases to a conceptually new strategy in heavy element double bonds chemistry where visible light is at the front seat of bond activation. [ABSTRACT FROM AUTHOR]

N,O‐acetals are found as structural motifs in natural products and are important synthetic precursors for N‐acylimines as building blocks in organic synthesis for C−C‐bond formation and amines. For the synthesis of N,O‐acetals, an acid‐, base‐ and metal‐free catalytic method is reported applying N,N‐di‐(2,6‐diisopropyl)‐1,7‐dicyano‐perylen‐3,4,9,10‐tetracarboxylic acid imide and N,N‐di‐(2,6‐diisopropyl)‐1,6,7,12‐tetrabromo‐2,5,8,11‐tetracyano‐perylen‐3,4,9,10‐tetracarboxylic acid imide as extremely electron‐deficient photocatalysts. The first perylene bisimide highly selectively photocatalyzes the formation of the N,O‐acetals as products in high yields, and the second and more electron‐deficient perylene bisimide allows these reactions without thiophenol as an H‐atom transfer reagent. Calculated electron density maps support this. The reaction scope comprises different substituents at the nitrogen of the enamides and different alcohols as starting material. Dehydroalanines are converted to non‐natural amino acids which shows the usefulness of this method for organic and medicinal chemistry. [ABSTRACT FROM AUTHOR]