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Dipole-bound states in anions exist when a polar neutral core binds an electron in a diffuse orbital through charge–dipole interaction. Electronically excited polar neutral cores can also bind an electron in a diffuse orbital to form Core-Excited Dipole-Bound States (CE-DBSs), which are difficult to observe because they usually lie above the electron detachment threshold, leading to very short lifetimes and, thus, unstructured transitions. We report here the photodetachment spectroscopy of cryogenically cooled acetylacetonate anion (C5H7O2−) recorded by detecting the neutral radical produced upon photodetachment and the infrared spectroscopy in He-nanodroplets. Two DBSs were identified in this anion. One of them lies close to the electron detachment threshold (∼2.74 eV) and is associated with the ground state of the radical (D0-DBS). Surprisingly, the other DBS appears as resonant transitions at 3.69 eV and is assigned to the CE-DBS associated with the first excited state of the radical (D1-DBS). It is proposed that the resonant transitions of the D1-DBS are observed ∼1 eV above the detachment threshold because its lifetime is determined by the internal conversion to the D0-DBS, after which the fast electron detachment takes place. [ABSTRACT FROM AUTHOR]

We report the x-ray absorption spectrum (XAS) of the tert-butyl radical, C4H9. The radical was generated pyrolytically from azo-tert-butane, and the XAS of the pure radical was obtained by subtraction of spectra recorded at different temperatures. The bands in the XAS were assigned by ab initio calculations that are in very good agreement with the experimental data. The lowest energy signal in the XAS is assigned to the C1s electron transition from the central carbon atom to the singly occupied molecular orbital (SOMO), while higher transitions correspond to C1s excitations from terminal carbon atoms. Furthermore, we investigated the fragmentation of the radical following resonant C1s excitation by electron–ion-coincidence spectroscopy. Several fragmentation channels were identified. The C1s excitation of the terminal carbons is associated with a stronger fragmentation tendency compared to the lowest C1s excitation of the central carbon into the SOMO. For this core excited state, we still observe an intact parent ion, C 4 H 9 + , and a comparatively higher tendency to dissociate into CH 3 + + C 3 H 6 + . [ABSTRACT FROM AUTHOR]

Reliable thermodynamic and kinetic properties of free radical polymerization reactions are essential for synthesizing both primary polymeric materials and specialty polymers. The computational generation of these data from quantum chemistry requires a time-efficient method capable of capturing the essential physics. One such method, fixed-node diffusion Monte Carlo (FN-DMC) (using single Slater–Jastrow trial wavefunctions), has demonstrated the capability to recover 90%–95% of missing dynamic correlation energy for typical systems. In this study, methyl radical addition to ethylene serves as a simple model to test FN-DMC's ability to calculate enthalpies of reaction and activation energies with different time steps, antisymmetric trial wavefunctions, basis set sizes, and effective core potentials. The FN-DMC computational protocol thus defined for methyl radical addition to ethylene is subsequently benchmarked against Weizmann-1 and experimental reaction enthalpies from Lin et al.'s test set of 21 radical addition and 28 hydrogen abstraction enthalpies. Our findings reveal that FN-DMC consistently generates reaction enthalpies with chemical accuracy, exhibiting mean absolute deviation of 3.5(7) and 1.4(8) kJ/mol from the Weizmann-1 reference for radical addition and hydrogen abstraction reactions, respectively. Given its favorable computational scaling and high degree of parallelizability, we, therefore, recommend more comprehensive testing of FN-DMC with effective core potentials to address more extensive and intricate polymerization reactions and reactions with other radicals. [ABSTRACT FROM AUTHOR]

Infrared (IR) action spectroscopy is utilized to characterize carbon-centered hydroperoxy-cyclohexyl radicals (·QOOH) transiently formed in cyclohexane oxidation. The oxidation pathway leads to three nearly degenerate ·QOOH isomers, β-, γ-, and δ-QOOH, which are generated in the laboratory by H-atom abstraction from the corresponding ring sites of the cyclohexyl hydroperoxide (CHHP) precursor. The IR spectral features of jet-cooled and stabilized ·QOOH radicals are observed from 3590 to 7010 cm−1 (∼10–20 kcal mol−1) at energies in the vicinity of the transition state (TS) barrier leading to OH radicals that are detected by ultraviolet laser-induced fluorescence. The experimental approach affords selective detection of β-QOOH, arising from its significantly lower TS barrier to OH products compared to γ and δ isomers, which results in rapid unimolecular decay and near unity branching to OH products. The observed IR spectrum of β-QOOH includes fundamental and overtone OH stretch transitions, overtone CH stretch transitions, and combination bands involving OH or CH stretch with lower frequency modes. The assignment of β-QOOH spectral features is guided by anharmonic frequencies and intensities computed using second-order vibrational perturbation theory. The overtone OH stretch (2νOH) of β-QOOH is shifted only a few wavenumbers from that observed for the CHHP precursor, yet they are readily distinguished by their prompt vs slow dissociation rates to OH products. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are widely recognized as catalysts for interstellar H2 formation. Extensive exploration into the catalytic potential of various PAHs has encompassed both theoretical investigations and experimental studies. In the present study, we focused on studying the reactivity of an imperfect aromatic molecule, indene (C9H8), and its hydrogenated counterpart, indane (C9H10), as potential catalysts for H2 formation within the interstellar medium. The reactions of these molecules with H atoms at 3.1 K were investigated experimentally using the para-H2 matrix isolation technique. Our experimental results demonstrate that both indene and indane are reactive toward H atoms. Indene can participate in H-atom-abstraction and H-atom-addition reactions, whereas indane primarily undergoes H-atom-abstraction reactions. The H-atom-abstraction reaction of indene results in the formation of the 1-indenyl radical (R1) (C9H7) and H2 molecule. Simultaneously, an H-atom-addition reaction forms the 1,2-dihydro-indene-3-yl radical (R2) (C9H9). Experiments also reveal that the H-atom-abstraction reaction of indane also produces the R2 radical. To the best of our knowledge, this study represents the first reporting of the infrared spectra of R1 and R2 radicals. The experimental results, combined with theoretical findings, suggest that indane and indene may play a role in the catalytic formation of interstellar H2. Furthermore, these results imply a quasi-equilibrium between the investigated molecules and the formed radicals via H-atom-addition and H-atom-abstraction reactions. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are widely recognized as catalysts for interstellar H2 formation. Extensive exploration into the catalytic potential of various PAHs has encompassed both theoretical investigations and experimental studies. In the present study, we focused on studying the reactivity of an imperfect aromatic molecule, indene (C9H8), and its hydrogenated counterpart, indane (C9H10), as potential catalysts for H2 formation within the interstellar medium. The reactions of these molecules with H atoms at 3.1 K were investigated experimentally using the para-H2 matrix isolation technique. Our experimental results demonstrate that both indene and indane are reactive toward H atoms. Indene can participate in H-atom-abstraction and H-atom-addition reactions, whereas indane primarily undergoes H-atom-abstraction reactions. The H-atom-abstraction reaction of indene results in the formation of the 1-indenyl radical (R1) (C9H7) and H2 molecule. Simultaneously, an H-atom-addition reaction forms the 1,2-dihydro-indene-3-yl radical (R2) (C9H9). Experiments also reveal that the H-atom-abstraction reaction of indane also produces the R2 radical. To the best of our knowledge, this study represents the first reporting of the infrared spectra of R1 and R2 radicals. The experimental results, combined with theoretical findings, suggest that indane and indene may play a role in the catalytic formation of interstellar H2. Furthermore, these results imply a quasi-equilibrium between the investigated molecules and the formed radicals via H-atom-addition and H-atom-abstraction reactions. [ABSTRACT FROM AUTHOR]

One of the most reactive intermediates for oxidative reactions is the oxyl radical, an electron-deficient oxygen atom. The discovery of a new vibration upon photoexcitation of the oxygen evolution catalysis detected the oxyl radical at the SrTiO3 surface. The vibration was assigned to a motion of the sub-surface oxygen underneath the titanium oxyl (Ti–O●−) created upon hole transfer to (or electron extraction from) a hydroxylated surface site. Evidence for such an interfacial mode is derived from its spectral shape, which exhibited a Fano resonance—a coupling of a sharp normal mode to continuum excitations. Here, this Fano resonance is utilized to derive precise formation kinetics of the oxyl radical and its associated potential energy surface (PES). From the Fano lineshape, the formation kinetics are obtained from the anti-resonance (the kinetics of the coupling factor), the resonance (the kinetics of the coupled continuum excitations), and the frequency integrated spectrum (the kinetics of the normal mode's cross-section). All three perspectives yield logistic function growth with a half-rise of 2.3 ± 0.3 ps and a time constant of 0.48 ± 0.09 ps. A non-equilibrium transient associated with photoexcitation is separated from the rise of the equilibrated PES. The logistic function characterizes the oxyl coverage at the very initial stages (t ∼ 0) to have an exponential growth rate that quickly decreases toward zero as a limiting coverage is reached. Such time-dependent reaction kinetics identify a dynamic activation barrier associated with the formation of a PES and quantify it for oxyl radical coverage. [ABSTRACT FROM AUTHOR]

Recent years have seen an explosion of interest in organic radicals due to their promise for highly efficient organic light-emitting diodes and molecular qubits. However, accurately and inexpensively computing their electronic structure has been challenging, especially for excited states, due to the spin-contamination problem. Furthermore, while alternacy or "pseudoparity" rules have guided the interpretation and prediction of the excited states of closed-shell hydrocarbons since the 1950s, similar general rules for hydrocarbon radicals have not to our knowledge been found yet. In this article, we present solutions to both of these challenges. First, we combine the extended configuration interaction singles method with Pariser–Parr–Pople (PPP) theory to obtain a method that we call ExROPPP (Extended Restricted Open-shell PPP) theory. We find that ExROPPP computes spin-pure excited states of hydrocarbon radicals with comparable accuracy to experiment as high-level general multi-configurational quasi-degenerate perturbation theory calculations but at a computational cost that is at least two orders of magnitude lower. We then use ExROPPP to derive widely applicable rules for the spectra of alternant hydrocarbon radicals, which are completely consistent with our computed results. These findings pave the way for highly accurate and efficient computation and prediction of the excited states of organic radicals. [ABSTRACT FROM AUTHOR]

Electron spin relaxation is, on many occasions, considered an elephant in the room that challenges the idea of a radical-pair compass, a leading hypothesis for the navigation of migratory avian species. It has been widely recognized that an effective radical-pair magnetoreceptor requires a relaxation time that is long enough for an external magnetic field as weak as the geomagnetic field to significantly modify the coherent spin dynamics. However, previous studies proposed that certain spin relaxation, far quicker than the radical recombination reactions, could enhance, rather than degrade, the directional sensitivity of a radical-pair magnetoreceptor. Here, I investigate relaxation effects on the singlet–triplet interconversion of a model radical pair and find that the enhancement effect originates from population relaxation over a period of several microseconds as a result of efficient spin decoherence. Insights into the truncated spin systems shed light on the physics behind them. I further investigate the possibilities of such enhancement in cryptochrome-based magnetoreception, in which electron hopping takes place between tryptophan residues. [ABSTRACT FROM AUTHOR]

The α-hydroxyethyl radical (CH3·CHOH, 2A) is a key intermediate in ethanol biochemistry, combustion, atmospheric chemistry, radiation chemistry, and astrochemistry. Experimental data on the vibrational spectrum of this radical are crucially important for reliable detection and understanding of the chemical dynamics of this species. This study represents the first detailed experimental report on the infrared absorption bands of the α-hydroxyethyl radical complemented by ab initio computations. The radical was generated in solid para-H2 and Xe matrices via the reactions of hydrogen atoms with matrix-isolated ethanol molecules and radiolysis of isolated ethanol molecules with x rays. The absorption bands with maxima at 3654.6, 3052.1, 1425.7, 1247.9, 1195.6 (1177.4), and 1048.4 cm−1, observed in para-H2 matrices appearing upon the H· atom reaction, were attributed to the OHstr, α-CHstr, CCstr, COstr + CCObend, COstr, and CCstr + CCObend vibrational modes of the CH3·CHOH radical, respectively. The absorption bands with the positions slightly red-shifted from those observed in para-H2 were detected in both the irradiated and post-irradiation annealed Xe matrices containing C2H5OH. The results of the experiments with the isotopically substituted ethanol molecules (CH3CD2OH and CD3CD2OH) and the quantum-chemical computations at the UCCSD(T)/L2a_3 level support the assignment. The photolysis with ultraviolet light (240–300 nm) results in the decay of the α-hydroxyethyl radical, yielding acetaldehyde and its isomer, vinyl alcohol. A comparison of the experimental and theoretical results suggests that the radical adopts the thermodynamically more stable anti-conformation in both matrices. [ABSTRACT FROM AUTHOR]

Homogeneous solar fuels photocatalytic systems often require several additives in solution with the catalyst to operate, such as a photosensitizer (PS), Brønsted acid/base, and a sacrificial electron donor (SED). Tertiary amines, in particular triethylamine (TEA) and triethanolamine (TEOA), are ubiquitously deployed in photocatalysis applications as SEDs and are capable of reductively quenching the PS's excited state. Upon oxidation, TEA and TEOA form TEA•+ and TEOA•+ radical cations, respectively, which decay by proton transfer to generate redox non-innocent transient radicals, TEA• and TEOA•, respectively, with redox potentials that allow them to participate in an additional electron transfer step, thus resulting in net one-photon/two-electron donation. However, the properties of the TEA• and TEOA• radicals are not well understood, including their reducing powers and kinetics of electron transfer to catalysts. Herein, we have used both pulse radiolysis and laser flash photolysis to generate TEA• and TEOA• radicals in CH3CN, and combined with UV/Vis transient absorption and time-resolved mid-infrared spectroscopies, we have probed the kinetics of reduction of the well-established CO2 reduction photocatalyst, fac-ReCl(bpy)(CO)3 (bpy = 2,2′-bipyridine), by these radicals [kTEA• = (4.4 ± 0.3) × 109 M−1 s−1 and kTEOA• = (9.3 ± 0.6) × 107 M−1 s−1]. The ∼50× smaller rate constant for TEOA• indicates, that in contrast to a previous assumption, TEA• is a more potent reductant than TEOA• (by ∼0.2 V, as estimated using the Marcus cross relation). This knowledge will aid in the design of photocatalytic systems involving SEDs. We also show that TEA can be a useful radiolytic solvent radical scavenger for pulse radiolysis experiments in CH3CN, effectively converting unwanted oxidizing radicals into useful reducing equivalents in the form of TEA• radicals. [ABSTRACT FROM AUTHOR]

We report state-of-the-art first-principles molecular dynamics results on the heterogeneous chemical uptake of NO2, a major anthropogenic pollutant, on the dry and wet hydroxylated surface of α-quartz, which is a significant component of silica-based catalysts and atmospheric dust aerosols. Our investigation spotlights an unexpected chemical pathway by which NO2 (i) can be adsorbed as HONO by deprotonation of interfacial silanols (i.e., –Si–OH group) on silica, (ii) can be barrierless converted to nitric acid, and (iii) can finally dissociated to surface bounded NO and hydroxyl gas phase radicals. This chemical pathway does not invoke any previously experimentally postulated NO2 dimerization, dimerization that is less likely to occur at low NO2 concentrations. Moreover, water significantly catalyzes the HONO formation and the dissociation of nitric acid into surface-bounded NO and OH radicals, while visible light adsorption can further promote these chemical transformations. This work highlights how water-restricted solvation regimes on common mineral substrates are likely to be a source of reactive oxygen species, and it offers a theoretical framework for further and desirable experimental efforts, aiming to better constrain trace gases/mineral interactions at different relative humidity conditions. [ABSTRACT FROM AUTHOR]

The optical spectra of the palladium monosulfide (PdS) molecule in gas phase have been investigated for the first time through laser-induced fluorescence (LIF) and single-vibronic-level (SVL) emission spectroscopies. The I3Σ− − X3Σ− transition system containing 16 vibronic bands was identified in the LIF spectra, covering the energy range of 22 030–23 400 cm−1. The spectra with rotational resolution allowed for the determination of the molecular constants in both the ground X and excited I electronic states, involving the spin–orbit splitting, rotational constant, vibrational frequency, and isotope shift. Isotopically resolved SVL emission spectra permitted the observation of the spin–orbit splitting, vibrational frequency, and vibrational isotope shift of the X3Σ−0+,1 and A3Π2,1,0−,0+ states as they transitioned from the excited I state to the vibrational levels of the X and A states. Ab initio calculations presented plenty of the Λ-S and Ω states of PdS below 28 000 cm−1 and provided strong support for the assignments of the experimental observation. [ABSTRACT FROM AUTHOR]

Absolute line strengths of several transitions in the ν1 fundamental band of the hydroxyl radical (OH) have been measured by simultaneous determination of hydrogen peroxide (H2O2) and OH upon laser photolysis of H2O2. Based on the well-known quantum yield for the generation of OH radicals in the 248-nm photolysis of H2O2, the line strength of the OH radicals can be accurately derived by adopting the line strength of the well-characterized transitions of H2O2 and analyzing the difference absorbance time traces of H2O2 and OH obtained upon laser photolysis. Employing a synchronized two-color dual-comb spectrometer, we measured high-resolution time-resolved absorption spectra of H2O2 near 7.9 µm and the OH radical near 2.9 µm, simultaneously, under varied conditions. In addition to the studies of the line strengths of the selected H2O2 and OH transitions, the kinetics of the reaction between OH and H2O2 were investigated. A pressure-independent rate coefficient kOH+H2O2 was determined to be [1.97 (+0.10/−0.15)] × 10−12 cm3 molecule−1 s−1 at 296 K and compared with other experimental results. By carefully analyzing both high-resolution spectra and temporal absorbance profiles of H2O2 and OH, the uncertainty of the obtained OH line strengths can be achieved down to <10% in this work. Moreover, the proposed two-color time-resolved dual-comb spectroscopy provides a new approach for directly determining the line strengths of transient free radicals and holds promise for investigations on their self-reaction kinetics as well as radical–radical reactions. [ABSTRACT FROM AUTHOR]

Polariton chemistry may provide a new means to control molecular reactivity, permitting remote, reversible modification of reaction energetics, kinetics, and product yields. A considerable body of experimental and theoretical work has already demonstrated that strong coupling between a molecular vibrational mode and the confined electromagnetic field of an optical cavity can alter chemical reactivity without external illumination. However, the mechanisms underlying cavity-altered chemistry remain unclear in large part because the experimental systems examined previously are too complex for detailed analysis of their reaction dynamics. Here, we experimentally investigate photolysis-induced reactions of cyanide radicals with strongly-coupled chloroform (CHCl3) solvent molecules and examine the intracavity rates of photofragment recombination, solvent complexation, and hydrogen abstraction. We use a microfluidic optical cavity fitted with dichroic mirrors to facilitate vibrational strong coupling (VSC) of the C–H stretching mode of CHCl3 while simultaneously permitting optical access at visible wavelengths. Ultrafast transient absorption experiments performed with cavities tuned on- and off-resonance reveal that VSC of the CHCl3 C–H stretching transition does not significantly modify any measured rate constants, including those associated with the hydrogen abstraction reaction. This work represents, to the best of our knowledge, the first experimental study of an elementary bimolecular reaction under VSC. We discuss how the conspicuous absence of cavity-altered effects in this system may provide insights into the mechanisms of modified ground state reactivity under VSC and help bridge the divide between experimental results and theoretical predictions in vibrational polariton chemistry. [ABSTRACT FROM AUTHOR]

Chiral molecules can act as spin filters, preferentially transmitting electrons with spins polarized along their direction of travel, an effect known as chirality-induced spin selectivity (CISS). In a typical experiment, injected electrons tunnel coherently through a layer of chiral material and emerge spin-polarized. It is also possible that spin polarization arises in radical pairs formed photochemically when electrons hop incoherently between donor and acceptor sites. Here we aim to identify the magnetic properties that would optimise the visibility of CISS polarization in time-resolved electron paramagnetic resonance (EPR) spectra of transient radical pairs without the need to orient or align their precursors. By simulating spectra of actual and model systems, we find that CISS contributions to the polarization should be most obvious when at least one of the radicals has small g-anisotropy and an inhomogeneous linewidth larger than the dipolar coupling of the two radicals. Under these conditions there is extensive cancellation of absorptive and emissive enhancements making the spectrum sensitive to small changes in the individual EPR line intensities. Although these cancellation effects are more pronounced at lower spectrometer frequencies, the spectral changes are easier to appreciate with the enhanced resolution afforded by high-frequency EPR. Consideration of published spectra of light-induced radical pairs in photosynthetic bacterial reaction centres reveals no significant CISS component in the polarization generated by the conventional spin-correlated radical pair mechanism. [ABSTRACT FROM AUTHOR]

We study the electronic spin flux (atomic-scale flow of the spin density in molecules) by a perturbation analysis and ab initio nonadiabatic calculations. We derive a general perturbative expression of the charge and spin fluxes and identify the driving perturbation of the fluxes to be the time derivative of the electron-nucleus interaction term in the Hamiltonian. We then expand the expression in molecular orbitals so as to identify relevant components of the fluxes. Our perturbation theory describes the electronic fluxes in the early stage of reactions in an intuitively clear manner. The perturbation theory is then applied to an analysis of the spin flux obtained in ab initio calculations of the radical reaction of O2 and CH3· starting from three distinct spin configurations; (a) CH3· and triplet O2 with total spin of the system set S t o t = 1 / 2 (b) CH3· and singlet O2, S t o t = 1 / 2 , and (c) CH3· and triplet O2, S t o t = 3 / 2. Further analysis of the time-dependent behaviors of the spin flux in these numerical simulations reveals (i) the spin flux induces rearrangement of the local spin structure, such as reduction of the spin polarization arising from the triplet O2 and (ii) the spin flux flows from O2 to CH3· in the reaction starting from spin configuration (a) and from CH3· to O2 in that starting from configuration (b), whereas no major intermolecular spin flux was observed in that starting from configuration (c). Our study thus establishes the mechanism of the spin flux that rearranges the local spin structures associated with chemical bonds. [ABSTRACT FROM AUTHOR]

The unique physical properties of carbyne, a novel carbon nanostructure, have attracted considerable interest in modern nanotechnology. While carbyne synthesis has been accomplished successfully using diverse techniques, the underlying mechanisms governing the carbon monoxide-dependent catalytic synthesis of endohedral carbyne remain poorly understood. In this simulation-based study, we investigate the synthesis of endohedral carbyne from carbon and carbon monoxide radicals in the presence of a nickel catalyst inside double-walled carbon nanotubes with a (5,5)@(10,10) structure. The outcome of our investigation demonstrates that the incorporation of the carbon atom within the Nin@(5,5)@(10,10) model system initiates the formation of an elongated carbon chain. In contrast, upon the introduction of carbon monoxide radicals, the growth of the carbyne chain is inhibited as a result of the oxidation of endohedral nickel clusters by oxygen atoms after the initial steps of nucleation. Our findings align with prior theoretical, simulation, and experimental investigations, reinforcing their consistency and providing valuable insights into the synthesis of carbyne-based nanodevices that hold promising potential for future advancements in nanotechnology. [ABSTRACT FROM AUTHOR]

The aggregation of plastic waste results in immiscible polymer blends with inferior properties. This study explores the application of irradiation technology on polymer processing for its potential to increase the compatibility of immiscible polymer blends composed of polyethylene terephthalate) (PET) and linear low-density polyethylene (LLDPE). When PET is radiated, it undergoes chain-scission reactions resulting in the formation of free radicals. The extended lifespan of these free radicals in post-irradiated PET provides an opportunity for inducing interface reactions with LLDPE during compounding through reactive extrusion. PET was irradiated with up to 50 and 200 kGy irradiation absorbance doses of gamma irradiation and then compounded with LLDPE in a twin-screw extruder at three blend compositions. Analysis of rheological, morphological, and mechanical properties demonstrates the compatibility improvement in this immiscible polymer blend attributed to irradiation-induced free radical interface reactions using post-irradiated PET up to 50 kGy to conduct the reactive extrusion process. Highlights * Reactive extrusion process with post-irradiated PET. * Formation of interface reactions. * Improving the compatibility of immiscible polymer blend. KEYWORDS immiscible polymer blends, irradiation-induced interface reactions, plastics recycling, reactive extrusion, rheology, 1 | INTRODUCTION Recycling polymer-based multilayer films is extremely challenging due to their compositional heterogeneity, which offers multiple important functionalities. Production of flexible plastic packaging involves the lamination of multiple [...]

Cryptochrome 4a (Cry4a) has been proposed as the sensor at the heart of the magnetic compass in migratory songbirds. Blue-light excitation of this protein produces magnetically sensitive flavin–tryptophan radical pairs whose properties suggest that Cry4a could indeed be suitable as a magnetoreceptor. Here, we use cavity ring-down spectroscopy to measure magnetic field effects on the kinetics of these radical pairs in modified Cry4a proteins from the migratory European robin and from nonmigratory pigeon and chicken. B1/2, a parameter that characterizes the magnetic field-dependence of the reactions, was found to be larger than expected on the basis of hyperfine interactions and to increase with the delay between pump and probe laser pulses. Semiclassical spin dynamics simulations show that this behavior is consistent with a singlet–triplet dephasing (STD) relaxation mechanism. Analysis of the experimental data gives dephasing rate constants, rSTD, in the range 3–6 × 107 s−1. A simple "toy" model due to Maeda, Miura, and Arai [Mol. Phys. 104, 1779–1788 (2006)] is used to shed light on the origin of the time-dependence and the nature of the STD mechanism. Under the conditions of the experiments, STD results in an exponential approach to spin equilibrium at a rate considerably slower than rSTD. We attribute the loss of singlet–triplet coherence to electron hopping between the second and third tryptophans of the electron transfer chain and comment on whether this process could explain differences in the magnetic sensitivity of robin, chicken, and pigeon Cry4a's. [ABSTRACT FROM AUTHOR]

A hybrid stochastic simulation method is developed to study H2–O2 auto-ignition at the microscale. Simulation results show that the discrete and stochastic characteristics of reaction collisions have notable impacts on the ignition process, particularly in the early stages when only a few radicals exist. The statistical properties of ignition delay time, which reflect the accumulated stochasticity during ignition, are obtained and analyzed for different initial temperatures and total molecular numbers. It is found that the average and standard deviation of ignition delay time increase as the total molecular number decreases, with this phenomenon being particularly pronounced near the crossover temperature. When the total molecular number is sufficiently small, the chain initiation reaction becomes crucial to the stochastic properties, as its average firing time exhibits an inverse proportionality to the total molecular number. As the total molecular number increases, the influence of other chain reactions intensifies, causing the power law relation between standard deviation and total molecular number to shift from −1 power to −0.5 power. Owing to different chain reaction paths for high- and low-temperature auto-ignition, the strongest relative fluctuation occurs near the crossover temperature. A theoretical equation for the standard deviation of ignition delay time is obtained based on dimensional analysis, giving excellent agreement with the simulation results in both high- and low-temperature modes. [ABSTRACT FROM AUTHOR]

A new implementation of the orbital-based two-component relativistic configuration interaction approach is reported and applied to calculations of the electronic g-shifts of three diatomic radicals: AlO, HgF, and PdH. The new implementation augments efficient routines for the calculation of nonrelativistic Hamiltonians with new vectorized routines for the calculation of the action of the one-electron spin–orbit operator and allows efficient calculations for the expansion of generalized active space type. The program makes full use of double group as well as time-reversal symmetry. Particle–hole reorganization of the operators is used to improve the efficiency for expansions with nearly fully occupied orbital spaces. The flexibility of the algorithm and program is used to investigate the convergence of electronic g-shifts for the three diatomic radicals as functions of the active space, states included in the orbital optimization, and excitation levels. It was possible to converge to the valence limits within a few percent using expansions containing up to quadruple excitations. However, when excitations from the core orbitals were added, it was not possible to demonstrate convergence to within a few percent with expansions containing at most 10 × 109 determinants. [ABSTRACT FROM AUTHOR]

Rotational circular dichroism (RCD) has not been observed yet, but it is expected to deliver information about chiral molecules useful in many branches of chemistry. In the past, rather weak RCD intensities were predicted for model diamagnetic molecules and a limited number of rotational transitions. Here, we review quantum-mechanical foundations and simulate entire spectral profiles, including larger molecules, open-shell molecular radicals, and high-momentum rotational bands. Contribution of the electric quadrupolar moment was considered, but it turned out that it does not contribute to field-free RCD. Two conformers of a model dipeptide provided clearly distinct spectra. The dissymmetry Kuhn parameter gK predicted for the diamagnetic molecules even for high-J transitions rarely exceeded 10−5, and the simulated RCD spectra were often biased to one sign. In the radicals, the coupling of the rotational angular momentum with the spin for some transitions raised gK to about 10−2, and the RCD pattern was more conservative. In the resultant spectra, many transitions had negligible intensities due to small populations of the involved states, and a convolution with a spectral function made the typical RCD/absorption ratios about 100-times smaller (gK ∼ 10−4). This is still comparable with values typical for electronic or vibrational circular dichroism, and paramagnetic RCD is thus likely to be measurable relatively easily. [ABSTRACT FROM AUTHOR]

The regioselective radical CH trifluoromethylation of aromatic compounds have been shown to proceed in good yield and high regioselectivity when cyclodextrin (CD) is present. Yet, the reaction mechanism and the role of CD during the reaction have remained obscure. To this end, here we performed density functional theory (DFT) calculations to the conformations obtained by semiempirical quantum mechanical molecular dynamics calculations to reveal the reaction mechanism and the role of CD in controlling regioselectivity. The results show that metal salt increases the yield but do not affect the regioselectivity, which we further confirmed by an experiment. In contrast, multiple CD‐substrate complex conformations and reaction pathways were obtained, and CD was shown to contribute to improving the regioselectivity by stabilizing the intermediate state via encapsulation. The present study indicates that CDs can increase the regioselectivity by stabilizing the intermediate and product states while only marginally affecting the transition state. [ABSTRACT FROM AUTHOR]

5-endo-trig radical cyclization has long been recognized as one of the most straightforward ways for the construction of densely functionalized five-membered rings. Nevertheless, according to Baldwin's rules, the 5-endo-trig radical cyclization is kinetically disfavored due to stereoelectronic effects and thus usually proceeds via a slow rate, which renders its application a challenging task. In recent years, with the emergence of efficient radical generation methods and effective cyclization strategies, 5-endo-trig radical cyclization has been successfully accelerated to a synthetically useful rate and has been utilized in the access of diverse five-membered carbo- and heterocyclic compounds. This review comprehensively summarizes the methodologies involving the 5-endo-trig radical cyclization process, with particular emphasis on the elucidation of the promoting strategies, which include the polar effect, geometrical constraints, spin delocalization effect, and persistent radical effect. Each of these strategies is discussed in detail, with illustrative examples from recent literature studies to highlight their practical applications and effectiveness. It is anticipated that the in-depth understanding of the 5-endo-trig radical cyclization provided by this review would inspire further innovation of this privileged reaction mode and expand its applications. Moreover, the potent ring-closure-promoting strategies revealed herein would also contribute to achieving other challenges of cyclizations with particular significance for organic synthesis. [ABSTRACT FROM AUTHOR]

TBRT and ATRP are orthogonal initiation chemistries used in vinyl polymerisations. Here, we present the first combination of these techniques to readily create high molecular weight branched polyester macroinitiators capable of forming star copolymers from a range of methacrylate monomers. [ABSTRACT FROM AUTHOR]

A comprehensive computational study on the underlying reactivity of iron tetra-NHC complexes for C2 + N1 aziridination catalysis is presented. A library of 18 unique iron tetra-NHC complexes was constructed, and a computational screening was performed on the reaction barriers associated with the ratedetermining step (formation of an open chain radical intermediate). Thermodynamic barriers were computed along with a variety of steric and electronic properties, including the percentage of buried volume, orbital energies and ETS-NOCV analysis, which were used to identify key characteristics related to reactivity. The analysis performed in this study successfully identified key differences in tetracarbenes, such as linking groups (BMe2 or CH2) and the identity of the NHC groups (imidazole, imidazoline or benzimidazole) in terms of sterics, electronics and thermodynamics. Additionally, we have proposed two reaction pathways based on electronic structure arguments for the formation of the key open-chain radical intermediate. The first reaction pathway proceeds through a s-hole channel where the Fe(IV)-imide intermediate evolves into Fe(III)-imidyl radical through electron donation into the antibonding s* orbital, while the second involves a Fe(III)-imidyl radical formed through a p-hole channel (donation into p*). These pathways are consistent with the isoelectronic iron(IV)-oxo species for hydrogen atom abstraction mechanisms and they can be used as descriptors of the rate-determining step of the aziridination reaction. [ABSTRACT FROM AUTHOR]

A CuII complex (1) of a bis-pyridine-dioxime ligand and its one-electron oxidized analog (1-ox) were thoroughly characterized by various spectroscopic techniques, including X-ray absorption spectroscopy. 1-ox was found to be a CuII complex of a ligand iminoxyl radical and represents the first example of such a type. Reorganization energy (λ) of 2.12 eV was determined for the 1-ox/1 couple, which is considerably higher than the type 1 protein and synthetic CuIII/II(OH) complexes. [ABSTRACT FROM AUTHOR]

Poly(styrene‐co‐maleic anhydride) (SMAnh) is a copolymer system that is well known for its alternating tendency, which has been thoroughly investigated by many research groups over the decades and is widely used in industry. Investigations have focused almost entirely on thermally initiated systems. However, very few investigations have been conducted on light‐initiated radical copolymerization. In this study, the photoinitiated copolymerization of styrene and maleic anhydride is investigated without the use of an external radical source, such as the classical 2,2‐azobis(2‐methylpropionitrile) (AIBN), benzoyl peroxide (BPO), or any photoinitiators. The initiation of the polymerization is instead found to take place through an excited state biradical generated in situ from a photoexcited charge‐transfer complex (CTC) comprising the donor (styrene) and acceptor (maleic anhydride) monomers. The formation of the complex is found to be solvent dependent. Excitation of the complex results in copolymerization of monomers to afford high‐molecular‐weight (>105 g·mol−1) alternating copolymers. [ABSTRACT FROM AUTHOR]

Photolysis of phenacyl benzoates tethered with a phenol or anisole in acetone resulted in the formation of 1,4‐dicarbonyl compounds, coupling products of the phenacyl moiety with acetone. The reaction occurs via electron and/or proton transfer from a triplet exciplex, leading to the formation of a phenacyl radical, which then adds to the enol form of acetone. The reaction also occurs in intermolecular fashion with external electron donors. [ABSTRACT FROM AUTHOR]

The visible light-promoted O-alkenylation of phenols and naphthols with terminal alkynes is achieved using 2,4,6-tris(4-fluorophenyl)pyrylium tetrafluoroborate (T(p-F)PPT) as a photocatalyst at room temperature without the need of any external ligand or additive. Apart from its excellent functional group tolerance, the protocol described herein represents an appealing alternative strategy to classical transition-metal catalysed hydroarylation reactions. Mechanistic investigations revealed that the reaction involves a radical pathway. The utility of the hydroarylated products for the synthesis of fused benzofurans via a one-pot annulation was also demonstrated. Herein, we report the first intermolecular radical hydroarylation of alkynes. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A visible‐light‐induced photoredox‐catalyzed regioselective and stereoselective C(sp2)–H amination of enamides with bench‐stable and easily accessible N‐aminopyridium salts is developed, affording synthetically and biologically prominent vicinal 1,2‐diamine scaffolds with broad substrate scope and excellent functional group compatibility. The transformation proceeded through a radical pathway involving the Giese addition of the relatively electrophilic N‐centered sulfonamidyl radical species to nucleophilic β‐olefinic position of enamides followed by the ensuing single electron oxidation and β‐H elimination, delivering geometrically‐defined Z‐configured β‐sulfonamidylated enamides. The operational simplicity, environmental friendliness and cost efficiency of this methodology allowed it to pave a new avenue to enrich the arsenal of synthetically crucial functionalized enamides and their related derivatives. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Compared to well‐established 1,5‐HAT of N‐centered radicals, the synthetic applications of 1,2‐HAT process were scarce due to the high barrier and constrained three‐membered transition state. Here, we have developed a novel C(sp3)‐H gem‐difluoroallylation via a base assisted formal 1,2‐HAT of amidyl radicals with the reductive quenching cycle of photocatalyst. This transformation enables the efficient formation of α‐aminoalkyl radicals via 1,2‐HAT and showcases good functional group tolerance. Our preliminary mechanistic experiments, along with Density Functional Theory (DFT) calculations demonstrate the feasibility of 1,2‐HAT of amidyl radicals, especially when assisted by a base. Furthermore, our method also succeeds in the Giese addition of electron‐deficient alkenes as well as styrene. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: CO2 is an abundant, nontoxic, and renewable C1 feedstock in synthetic chemistry. Direct carboxylation of readily available olefins incorporating CO2 is regarded as a promising strategy to access high value‐added carboxylic acids as well as CO2 fixation. However, due to the thermodynamic stability and kinetic inertness of CO2 and the difficulty in controlling the regioselectivity, the carboxylation of olefins with CO2 still remains challenging. Radical‐type functionalization with olefins represented a powerful protocol and enabled the development of novel transformations in this realm. More recently, the advance of new technology, such as photoredox catalysis and the renaissance of electrochemistry in organic synthesis, offered access to unique chemical reactivities of radical precursors and provided new solutions to the functionalization of olefins. This review presents the recent advances in the radical‐type carboxylation of olefins, which has mainly been achieved through photocatalysis and electrocatalysis in the last decade. In this article, we provide a comprehensive introduction of the progress, summarize the advantages and limitations of current research, and discuss the potential outlook for further development. Key Scientists: [ABSTRACT FROM AUTHOR]

Comprehensive Summary: The stability of organic radicals in ambient condition is important for their practical application. During the development of organic radical chemistry, the electron‐withdrawing and steric hindrance groups are usually introduced to improve the stability of radicals via reducing the reactivity of radicals with oxygen in air. Herein, the electron‐withdrawing carbonyl groups are introduced to construct a planar aromatic oxalic acid radical (IDF‐O8) with two‐dimensional electron spin pan structure. Interestingly, IDF‐O8 exhibited a low optical bandgap of 0.91 eV in film, however, the multiple quinone resonance structures between electron‐withdrawing ketone and phenol radicals contribute to the high stability of open‐shell radical IDF‐O8 without protection of large steric hindrance groups. Under the irradiation of 808 nm (1.2 W·cm–2), IDF‐O8 reaches 147 °C in powder state. This work provides an efficient synthesis route for the open‐shell electron spin pan system, which is different from the famous fullerene, carbon nanotube and graphene. The electron spin pan can be extended to spin tube or spin sphere system based on the design strategy of aromatic inorganic acid radicals in future. [ABSTRACT FROM AUTHOR]

A single-step phenylation at the non-acidic C(sp3)–H bond attached to the heteroatom of ethers and N -Boc-amines has been achieved using photoexcited 4-benzoylpyridine as a hydrogen atom transfer (HAT) catalyst. The design of electron-deficient (trifluoromethylsulfonyl)benzene derivatives, as a phenyl precursor, was critical to realizing the present transformation. Moreover, the DFT calculations indicated that the present transformation proceeds via a concerted homolytic aromatic substitution rather than via a stepwise one involving the formation of a cyclohexadienyl radical intermediate. [ABSTRACT FROM AUTHOR]

The current techniques for antithrombotic coating on blood‐contacting biomedical materials and devices are usually complex and lack practical feasibility with weak coating stability and low heparin immobilization. Here, a heparinized self‐healing polymer coating with inflammation modulation is introduced through thermal‐initiated radical copolymerization of methacrylate esterified heparin (MA‐heparin) with methyl methacrylate (MMA) and n‐butyl acrylate (nBA), followed by the anchoring of reactive oxygen species (ROS)‐responsive polyoxalate containing vanillyl alcohol (PVAX) onto the coating through esterification. The aspirin, which is readily dissolved in the solution of MMA and nBA, is encapsulated within the coating after copolymerization. The copolymerization of MA‐heparin with MMA and nBA significantly increases the heparin content of the coating, effectively inhibiting thrombosis and rendering the coating self‐healing to help maintain long‐term stability. ROS‐responsive PVAX and aspirin released in a temperature‐dependent manner resist acute and chronic inflammation, respectively. The heparinized self‐healing and inflammation‐modulated polymer coating exhibits the ability to confer long‐term stability and hemocompatibility to blood‐contacting biomedical materials and devices. Surface engineering for blood‐contacting biomedical devices paves a successful way to reduce thrombotic and inflammatory complications. However, lack of effectiveness, long‐term stability and practical feasibility hinders the development and clinical application of existing strategies. Here we design a heparinized self‐healing and inflammation‐modulated polymer coating, which possesses high heparin level and self‐healing capability to maintain long‐term stability. The polymer coating is practically feasible to varied substrates and demonstrated to manipulate inflammation and prevent thrombosis both in vitro and in vivo. Our work provides a new method to develop coatings for blood‐contacting biomedical materials and devices with long‐term stability and hemocompatibility. [Display omitted] [ABSTRACT FROM AUTHOR]

Comprehensive Summary: CO2 is an abundant, nontoxic, and renewable C1 feedstock in synthetic chemistry. Direct carboxylation of readily available olefins incorporating CO2 is regarded as a promising strategy to access high value‐added carboxylic acids as well as CO2 fixation. However, due to the thermodynamic stability and kinetic inertness of CO2 and the difficulty in controlling the regioselectivity, the carboxylation of olefins with CO2 still remains challenging. Radical‐type functionalization with olefins represented a powerful protocol and enabled the development of novel transformations in this realm. More recently, the advance of new technology, such as photoredox catalysis and the renaissance of electrochemistry in organic synthesis, offered access to unique chemical reactivities of radical precursors and provided new solutions to the functionalization of olefins. This review presents the recent advances in the radical‐type carboxylation of olefins, which has mainly been achieved through photocatalysis and electrocatalysis in the last decade. In this article, we provide a comprehensive introduction of the progress, summarize the advantages and limitations of current research, and discuss the potential outlook for further development. Key Scientists: [ABSTRACT FROM AUTHOR]

Subphthalocyanines (SubPcs) are aromatic chromophores with a bowlshaped structure and outstanding optoelectronic properties. The cavity formed by a C3-symmetry trispyridyl-SubPc, Pd(II)-metalloorganic capsule has proved an optimal, shape-complementary space for the complexation of C60. Taking advantage of the intense green light absorption of the SubPc components of the capsule, and their ability to transfer energy/electrons from the excited state, our group has recently described the unprecedented use of SubPc cages as molecular photoreactors to perform photoredox-triggered addition of diphenylamine radicals over encapsulated C60. Unfortunately, the reaction could only be performed using stoichiometric amounts of the cage due to inhibition of the SubPc cavity by the addition compound. Here, we describe the preparation of a more flexible SubPc cage built with a related C1-symmetry trispyridyl-SubPc (C1-SubPc-cage), which could facilitate the exchange between the complexed addition compound and pristine fullerene, thus allowing to use it in catalytic amounts. After assessing the ability of C1-SubPc-cage to host C60, the addition of α-aminoalkyl radicals in the presence of the cage under green light irradiation was tested. Curiously, optimisation of the reaction conditions (using catalytic amounts of C1-SubPc-cage in diluted solutions) rendered a different reaction outcome, that is, a cyclopropanated fullerene, in remarkably high yields. [ABSTRACT FROM AUTHOR]

Advanced oxysulfur radical-based advanced oxidation processes (OSR-AOPs) usually use heterogeneous catalysts to activate sulfite to degrade organic pollutants in water. In this study, we report the mechanism of sulfite activation by amorphous Fe1−xNixS to degrade rhodamine B (RhB) in different pH ranges. Compared with FeS, Fe1−xNixS had a wide pH application range and high activity. For Fe1−xNixS, Ni-doping sped up electron transfer inside the catalyst and the reduced S2− promoted the ≡Fe(III)/≡Fe(II) cycle, which together improved the sulfite activation by Fe1−xNixS. The results indicated a pH dependence of RhB degradation in the Fe1−xNixS/sulfite system. The free radical pathway of SO3˙−, SO5˙− and ˙OH generated in the process was dominant under acidic condition, whereas it was mainly a non-free radical pathway of electron transfer between the catalyst and the pollutant under alkaline conditions. Both free radical and non-free radical pathways existed in Fe1−xNixS/sulfite under neutral conditions. The results shed significant light on promoting sulfite-based AOPs to remove pollutants from water. [ABSTRACT FROM AUTHOR]

An efficient iodide ion (I−)-enabled method for direct α-C(sp3)–H triazolization of ethers via a radical cross-coupling has been developed for regioselective construction of N2-substituted hemiaminal ethers. The developed C(sp3)–H triazolization reaction features the resulting products in good yields (up to 90%) and an excellent functional group tolerance to various ethers, including cyclic and linear ethers. Preliminary mechanistic study and DFT calculation investigation indicate that the reaction proceeds via a SN2-like desulfonylation radical coupling process and an (I−)-involved ternary complex is responsible for the high conversion ratio and the high regioselectivity. I− not only promotes the process but also prevents the in situ generated carbon-centered radicals (CCRs) from being oxidized into carbon cations in an oxidative environment. [ABSTRACT FROM AUTHOR]

A metal-free photoinduced alkynylation of carbamoyl radicals with hypervalent iodine(III) reagents for a facile synthesis of alkynyl amides is described. This protocol features good functional group tolerance and a broad substrate scope for direct synthesis of alkynyl amide derivatives in good to excellent yields under mild and redox-neutral reaction conditions. The synthetic application is demonstrated by the late-stage installation of alkynyl amides into natural products and active pharmaceutical relevant molecules. The mechanistic studies indicated the simultaneous existence of photoredox catalytic and direct photoexcited processes, and the quantum yields confirmed the occurrence of the radical chain propagation process. [ABSTRACT FROM AUTHOR]

An unusual example of a potassium capped terminal cobalt–oxido complex has been isolated and crystallographically characterized. The synthesis of [tBu,TolDHP]CoOK proceeds from a previously reported parent compound, [tBu,TolDHP]CoOH, via deprotonation with KOtBu. Structural and electronic characterization suggest a weakly coupled dimer in a distinct seesaw geometry with a Co(III) oxidation state and a non-innocent radical ligand. [ABSTRACT FROM AUTHOR]

The kinetics of gelation in the Activators Regenerated by Electron Transfer Atom Transfer Radical Polymerization (ARGET ATRP) of styrene, using a bifunctional initiator and no crosslinking agents are investigated. By applying the method of moments, we develop a system of differential equations that accounts for the formation of polymer rings. The kinetic rate constants of this model are optimized on the experimentally determined kinetics, varying the reaction temperature and ethanol fraction. Subsequently, we explore how variations in the amounts of catalyst, initiator, and reducing agents affect the simulated equilibria of ARGET ATRP, the emergence of gelation, and the swelling properties of the resulting networks. These findings suggest that favoring ring formation enhances the gelation phenomenon, supporting the hypothesis that the networks formed under the reported reaction conditions are olympic gels. [ABSTRACT FROM AUTHOR]

The strategy for the preparation of polyisobutylene‐based block copolymers via mechanistic transformation from cationic to radical polymerization is reported. This strategy involves the synthesis of 2‐bromo‐2‐methylpropanoyl‐terminated difunctional polyisobutylene macroinitiator (BiBB‐PIB‐BiBB) via consecutive cationic polymerization, in situ preparation of hydroxyl‐terminated polyisobutylene and its acylation by 2‐bromo‐2‐methylpropanoyl bromide. The Mn2(CO)10−triggered photo‐induced radical polymerization of styrene in bulk using this macroinitiator leads to the formation of multiblock copolymer, while predominantly triblock copolymer is generated during the polymerization of methyl methacrylate. The possibility to functionalize the polyisobutylene by pyrene via photo‐induced radical addition of 1‐bromomethyl pyrene in the presence of Mn2(CO)10 is also demonstrated in this work. [ABSTRACT FROM AUTHOR]

Comprehensive Summary A visible‐light‐induced decarboxylative radical cascade cyclization reaction between N‐(2‐cyanoaryl)‐acrylamides and alkyl N‐(acyloxy)phthalimide (NHPI esters) for the construction of phenanthridine derivatives has been developed. This approach utilizes lithium iodide (LiI) and triphenylphosphine (PPh3) as the redox catalysts and the alkyl radical is produced through the photoactivation of the electron donor‐acceptor (EDA) complex. A series of primary, secondary, and tertiary alkyl‐substituted phenanthridines are prepared in up to 82% yield without transition‐metal catalysts, chemical oxidants, or metal‐/organic dye‐based photocatalysts. [ABSTRACT FROM AUTHOR]

Methanol is widely recognized as a carbon-neutral fuel. This work used synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) to study the oxidation process of water/methanol/n-heptane mixes in a jet-stirred reactor (JSR) at a pressure of 1 atm, equivalence ratios (ϕ) of 1 and a temperature range of 500–1100 K. The results of the experiment indicate that the inhibition of n-heptane's oxidation at low temperatures (500–740K) is the primary manifestation of the action of methanol/water mixtures on n-heptane oxidation. The strong interactions among the components of water/methanol/n-heptane mixtures at low temperatures are primarily between methanol and n-heptane. The higher the methanol content, the greater the strength of inhibition of n-heptane oxidation. This inhibitory effect primarily results from the competition of methanol with ˙OH radicals. It is noteworthy that the chemical kinetic interactions between methanol-water mixtures and n-heptane not only manifest changes in the ˙OH radical pools but are also associated with the intermolecular chemical kinetic interactions between peroxyalkyl radicals (ROO˙) and CH 3 OH. • The oxidation of water/methanol/n-heptane blends had been studied by the SVUV-PIMS. • Quantitative analysis was conducted on several crucial oxidative intermediates. • The mechanistic model for water/methanol/n-heptane blends was optimized. • The inhibition of n-heptane oxidation by methanol-water mixtures was analyzed. • Chemical interactions between methanol-water mixtures and n-heptane are revealed. [ABSTRACT FROM AUTHOR]

Lithium salt-doped spiro-OMeTAD is widely used as a hole-transport layer (HTL) for high-efficiency n-i-p perovskite solar cells (PSCs), but unfortunately facing awkward instability for commercialization arising from the intrinsic Li+ migration and hygroscopicity. We herein demonstrate a superoxide radicals (•O2−) derived HTL of metal-free spiro-OMeTAD with remarkable capability of avoiding the conventional tedious oxidation treatment in air for highly stable PSCs. Present work explores the employing of variant-valence Eu(TFSI)2 salts that could generate •O2− for facile and adequate pre-oxidation of spiro-OMeTAD, resulting in the HTL with dramatically increased conductivity and work function. Comparing to devices adopting HTL with LiTFSI doping, the •O2−-derived spiro-OMeTAD increases the PSCs efficiency up to 25.45% and 20.76% for 0.05 cm2 active area and 6 × 6 cm2 module, respectively. State-of-art PSCs employing such metal-free HTLs are also demonstrated to show much-improved environmental stability even under harsh conditions, e.g., maintaining over 90% of their initial efficiency after 1000 h of operation at the maximum power point and after 80 light-thermal cycles under simulated low earth orbit conditions, respectively, indicating the potentials of developing metal-free spiro-OMeTAD for low-cost and shortened processing of perovskite photovoltaics. The migration and hygroscopicity of lithium salt in doped spiro-OMeTAD hampers the device efficiency of perovskite solar cells. Here, the authors employ Eu(TFSI)2 salts to generate superoxide radical for facile pre-oxidation, achieving enhanced efficiency and stability of solar cells and modules. [ABSTRACT FROM AUTHOR]

The valorization of native lignin to functionalized aromatic compounds under visible light is appealing yet challenging. In this communication, colloidal mercaptoalkanoic acid capped ultrathin ZnIn2S4 (ZIS) microbelts was successfully fabricated, which was used as a superior catalyst for depolymerization of native lignin in birch woodmeal under visible light, with an optimum yield of 28.8 wt % to functionalized aromatic monomers achieved in 8 h. The capped mercaptoalkanoic acid not only enables a solvent modulated reversible interchange of ZIS between the colloidal state for efficient reaction and the aggregated state for facile separation, but also serves as a precursor for light initiated generation of reactive thiyl radical for highly selective cleavage of β‐O‐4 bond in native lignin. This work provides a green and efficient strategy for the depolymerization of native lignin to functionalized aromatic monomers under mild conditions, which involves a new mechanism for the cleavage of β‐O‐4 bonds in native lignin. The capability of cleavage of β‐O‐4 bonds in native lignin by photogenerated thiyl radicals also demonstrates the great potential of using photogenerated thiyl radicals in organics transformations. [ABSTRACT FROM AUTHOR]

Supramolecular artificial light‐harvesting system with highly efficient host–guest energy transfer pathway provides an ideal platform for optimizing the photochemistry process. The consecutive photo‐induced electron transfer (conPET) process overcomes the energy limitation of visible‐light photocatalysis, but is often compromised by mismatching between the absorption of ground state dye and its radical, weakening the efficiency of photoredox reaction. By encapsulating a conPET photocatalyst rhodamine 6G into metal‐organic cage, the supramolecular approach was undertaken to tackle the intrinsic difficulty of matching the light absorption of photoexcitation between rhodamine 6G and its radical. The highly efficient Förster resonance energy transfer from the photoexcited cage to rhodamine 6G forced by host–guest encapsulation facilitates the conPET process for the single‐wavelength light‐driven activation of aryl halides by stabilizing and accelerating the production and accumulation of the rhodamine 6G radical intermediate. The tunable and flexible nature of the supramolecular host–guest complex renders the cage‐based encapsulation strategy promising for the development of ideal photocatalysts toward the better utilization of solar energy. [ABSTRACT FROM AUTHOR]