Among porous organic polymers (POPs), azo-linked POPs represent a crucial class of materials, making them the focus of numerous catalytic systems proposed for their synthesis. However, the synthetic process is limited to metal-catalyzed, high-temperature, and liquid-phase reactions. In this study, we employ mechanochemical oxidative metal-free systems to encompass various syntheses of azo-based polymers. Drawing inspiration from the "rule of six" principle (six or more carbons on azide group render the organic compound relatively safe), an azo compound featuring significant steric hindrance is obtained using the hypervalent iodine oxidation strategy. Furthermore, during the polymerization process, steric hindrance is enhanced in monomers to effectively prevent explosions resulting from direct contact between hypervalent iodine oxidants and primary amines. Indeed, this approach provides a facile and innovative solid-phase synthesis method for synthesizing azo-based materials.

Homoleptic and heteroleptic copper(I) complexes were anchored on silica nanoparticles and used for the visible-light mediated α-arylation of enol acetate.Photo-Catalyzed alpha-Arylation of Enol Acetate Using Recyclable Silica-Supported Heteroleptic and Homoleptic Copper(I) Photosensitizers (Troian-Gautier, Riant, Hermans et al.)

Abstract

Earth-abundant photosensitizers are highly sought after for light-mediated applications, such as photoredox catalysis, depollution and energy conversion schemes. Homoleptic and heteroleptic copper(I) complexes are promising candidates in this field, as copper is abundant and the corresponding complexes are easily obtained in smooth conditions. However, some heteroleptic copper(I) complexes suffer from low (photo)stability that leads to the gradual formation of the corresponding homoleptic complex. Such degradation pathways are detrimental, especially when recyclability is desired. This study reports a novel approach for the heterogenization of homoleptic and heteroleptic Cu complexes on silica nanoparticles. In both cases, the photophysical properties upon surface immobilization were only slightly affected. Excited-state quenching with aryl diazonium derivatives occurred efficiently (10⁸–10¹⁰ M⁻¹ s⁻¹) with heterogeneous and homogeneous photosensitizers. Moderate but almost identical yields were obtained for the α-arylation of enol acetate using the homoleptic complex in homogeneous or heterogeneous conditions. Importantly, the silica-supported photocatalysts were recycled with moderate loss in photoactivity over multiple experiments. Transient absorption spectroscopy confirmed that excited-state electron transfer occurred from the homogeneous and heterogeneous homoleptic copper(I) complexes to aryl diazonium derivatives, generating the corresponding copper(II) center that persisted for several hundreds of microseconds, compatible with photoredox catalysis applications.

Nitrogen-doped graphene quantum dots (NGQDs) synthesized from different ratios of carbon and nitrogen sources have been systematically explored for their electrochemiluminescence (ECL) properties for the first time. And NGQDs as signal molecules combined with photo-induced electron/energy transfer reversible addition-fragment chain transfer (PET-RAFT) signal amplification strategy to construct a ECL biosensor for sensitive detection of KRAS G12C mutation was first reported.

Abstract

The levels of KRAS G12C point mutation is recognized to be closely related to the earlier diagnosis of non-small cell lung cancer (NSCLC). Here, based on nitrogen-doped graphene quantum dots (NGQDs) and photo-induced electron/energy transfer reversible addition-fragment chain transfer (PET-RAFT) signal amplification strategy, we fabricated a novel electrochemiluminescence (ECL) biosensor for the detection of KRAS G12C mutation for the first time. NGQDs as ECL-emitting species with cathodic ECL were prepared by a simple calcination method. Firstly, KRAS G12C mutation DNA, i. e., target DNA (tDNA), was captured by specific identification with hairpin DNA (hDNA). Then, PET-RAFT was initiated by blue light, and large numbers of monomers were successfully polymerized to form controllable polymer chains. Lastly, massive NGQDs was introduced via amidation reaction with N-(3-aminopropyl)methacrylamide hydrochloride (APMA), which significantly amplified the ECL signal intensity. Under optimal conditions, this biosensor achieved a good linear relationship between ECL intensity and logarithm of the levels of KRAS G12C mutation in the range from 10 fM to 10 nM. Moreover, this strategy exhibited high selectivity and excellent applicability for KRAS G12C mutation detection in the serum samples. Therefore, this biosensor has great potential in clinical diagnosis and practical application.

A new family of heterometallic complexes, [Co^III ₂Ln^III(OMe)₂(naph)₂(O₂CMe)₃(MeOH)₂] (Ln=Tb (1), Dy (2), and Er (3)), possessing a rare {Co^III ₂Ln(μ₃-OMe)}⁸⁺ triangular core, have been prepared; compounds 2 and 3, as well as the magnetic diluted analogue {Co₂Dy_0.05Y_0.95} (2 a), behave as mononuclear single-molecule magnets (SMMs) with U_eff up to ~90 K.

Abstract

The first use of the Schiff base chelate N-naphthalidene-o-aminophenol (naphH₂) in Co/Ln chemistry has afforded a family of isostructural [Co^III ₂Ln^III(OMe)₂(naph)₂(O₂CMe)₃(MeOH)₂] (Ln=Tb, Dy and Er) complexes, revealing a rare {Co^III ₂Ln(μ₃-OMe)}⁸⁺ triangular core composed of two diamagnetic Co^III ions and a 4f-ion with slightly distorted square antiprismatic geometry. Alternating current (ac) magnetic susceptibility studies revealed that {Co₂Dy}, and its magnetic diluted analogue {Co₂Dy_0.05Y_0.95}, behave as mononuclear single-molecule magnets (SMMs) with similar energy barriers for the magnetization reversal, U_eff , of ~85-90 K. SMM properties were also detected for {Co₂Er}, with the compound exhibiting a U_eff of 18.7 K under an applied magnetic field of 800 Oe. To interpret the experimental magnetic results, ab initio CASSCF/RASSI-SO and DFT calculations were performed as a means of exploring the single-ion characteristics of Ln^III ions and comprehend the role of the diamagnetic Co^III ions in the magnetization relaxation of the three heterometallic compounds.

The electrosynthesis of partially fluorinated alkyl triflates and nonaflates by using electrochemical fluorination (ECF) has been developed; it provides access to CF₃SO₂OCH₂F and CF₃SO₂OCHF₂ as well as their deuterated analogs. Selected ethyl triflates and nonaflates are also accessible through ECF.

Abstract

A scalable straightforward synthesis of monofluoro- and difluoromethyl triflate CF₃SO₂OCH₂F (M^H2F ) and CF₃SO₂OCHF₂ (M^HF2 ) through electrochemical fluorination (ECF, Simons process) of methyl triflate M^H3 in anhydrous hydrogen fluoride at nickel anodes is presented. The ECF method is also feasible for the preparation of the deuterated analogues CF₃SO₂OCD₂F (M^D2F ) and CF₃SO₂OCDF₂ (M^D2F ). Surprisingly, no H/D exchange occurs during ECF of CF₃SO₂OCD₃ (M^D3 ); this provides further evidence for a NiF₃/NiF₄-mediated ECF mechanism. The ECF of selected partially fluorinated ethyl triflates is described, and electrochemical fluorination of CF₃SO₂OCH₂CF₃ (E^H2F3 ) leads to the until now unknown chiral CF₃SO₂OCHFCF₃ (E^HFF3 ). The analogous fluoromethyl and fluoroethyl nonaflates are also accessible by ECF. This study contains detailed spectroscopic, structural, and thermal data on (fluoro)methyl and fluoro(ethyl) triflates.

A methodological approach for the preparation of unconventional DTE-based photochromic phosphines is reported. It relies on the Pd-catalyzed annulation reaction of alkynyl phosphines in the presence of a silirene.

Abstract

The synthesis of phosphines with light controlled basicity is presented in this study. A methodological approach for the preparation of these unconventional photochromic phosphines based on a dithienylethene organic moiety is reported. It relies on the palladium-catalyzed annulation of alkynyl phosphines in the presence of a 2,3-Dithienylsilacyclopropene. Accordingly, a diphenyphosphino moiety is connected to the organic photochrome thanks to different linkers. Their influence on the photochromism and on the phosphinyl group basicity is studied and evaluated based on experimental an NMR descriptor as well as DFT calculations.

Core-shell structured Fe-based catalyst Na−Fe₃O₄@C with confinement effect delivered higher productivity of light olefins compared with the naked Na−Fe₂O₃ counterpart. Multiple characterization and DFT calculation verified that the timely carbon chain-growth termination, as well as unique CO₂/H₂ ratio and electronic property on the catalytic interface played vital roles in boosting light olefins synthesis.

Abstract

Even though Fe-based catalysts have been widely employed for CO₂ hydrogenation into hydrocarbons, oxygenates, liquid fuels, etc., the precise regulation of their physicochemical properties is needed to enhance the catalytic performance. Herein, under the guidance of the traditional concept in heterogeneous catalysis-confinement effect, a core-shell structured catalyst Na−Fe₃O₄@C is constructed to boost the CO₂ hydrogenation performance. Benefiting from the carbon-chain growth limitation, tailorable H₂/CO₂ ratio on the catalytic interface, and unique electronic property that all endowed by the confinement effect, the selectivity and space-time yield of light olefins (C₂ ⁼−C₄ ⁼) are as high as 47.4 % and 15.9 g mol_Fe ⁻¹ h⁻¹, respectively, which are all notably higher than that from the shell-less counterpart. The function mechanism of the confinement effect in Fe-based catalysts are clarified in detail by multiple characterization and density functional theory (DFT). This work may offer a new prospect for the rational design of CO₂ hydrogenation catalyst.

Electrochemical reductive cleavage of disulfides has been accomplished without the need for sacrificial metal anodes or a divided cell. Excellent conversion and selectivity toward the corresponding thiol can be achieved by tuning the current density at the electrodes. Very high current density at the anode creates a mass transfer barrier that impedes re-oxidation of the thiol generated at the cathode.

Abstract

Electroorganic synthesis is generally considered to be a green alternative to conventional redox reactions. Electrochemical reductions, however, are less advantageous in terms of sustainability, as sacrificial metal anodes are often employed. Divided cell operation avoids contact of the reduction products with the anode and allows for convenient solvent oxidation, enabling metal free greener electrochemical reductions. However, the ion exchange membranes required for divided cell operation on a commercial scale are not amenable to organic solvents, which hinders their applicability. Herein, we demonstrate that electrochemical reduction of oxidatively sensitive compounds can be carried out in an undivided cell without sacrificial metal anodes by controlling the mass transport to a small surface area electrode. The concept is showcased by an electrochemical method for the reductive cleavage of aryl disulfides. Fine tuning of the electrode surface area and current density has enabled the preparation of a wide variety of thiols without formation of any oxidation side products. This strategy is anticipated to encourage further research on greener, metal free electrochemical reductions.

Water-soluble arylazoisoxazoles are introduced as an additional scaffold to the existing arylazoheteroarenes and open the door for tailor-made properties in molecular and materials chemistry. They were found to combine excellent photochromic behavior with long thermal life times. Supramolecular aggregates were formed by host–guest interaction and gelation.

Abstract

Azoheteroarenes are emerging as powerful alternatives to azobenzene molecular photoswitches. In this study, water-soluble arylazoisoxazole photoswitches are introduced. UV/vis and NMR spectroscopy revealed moderate to very good photostationary states and reversible photoisomerization between the E- and Z-isomers over multiple cycles with minimal photobleaching. Several arylazoisoxazoles form host–guest complexes with β- and γ-cyclodextrin with significant differences in binding constants for each photoisomer as shown by isothermal titration calorimetry and NMR experiments, indicating their potential for photoresponsive host–guest chemistry in water. One carboxylic acid functionalized arylazoisoxazole can act as a hydrogelator, allowing gel properties to be manipulated reversibly with light. The hydrogel was characterized by rheological experiments, atom force microscopy and transmission electron microscopy. These results demonstrate that arylazoisoxazoles can find applications as molecular photoswitches in aqueous media.

Two photons are better than one: Intramolecular charge transfer in the intermediate radical cation of the N-phenylphenothiazines as photocatalysts improves the yields for borylation and phosphonylation of aryl chlorides.

Abstract

Aryl chlorides as substrates for arylations present a particular challenge for photoredox catalytic activation due to their strong C(sp²)−Cl bond and their strong reduction potential. Electron-rich N-phenylphenothiazines, as organophotoredox catalysts, are capable of cleaving aryl chlorides simply by photoinduced electron transfer without the need for an additional electrochemical activation setup or any other advanced photocatalysis technique. Due to the extremely strong reduction potential in the excited state of the N-phenylphenothiazines the substrate scope is high and includes aryl chlorides both with electron-withdrawing and electron-donating substituents. We evidence this reactivity for photocatalytic borylations and phosphonylations. Advanced time-resolved transient absorption spectroscopy in combination with electrochemistry was the key to elucidating and comparing the unusual photophysical properties not only of the N-phenylphenothiazines, but also of their cation radicals as the central intermediates in the photocatalytic cycle. The revealed photophysics allowed the excited-state and radical-cation properties to be fine-tuned by the molecular design of the N-phenylphenothiazines; this improved the photocatalytic activity.