Synthesis of Azuleno[1,2,3-]phenalene and Its π-Extended Buckybowl Derivative.

Azulene-fused molecular carbons have sparked intense research interest in recent years. Herein, we report a facile three-step synthesis of azuleno[1,2,3-]phenalene (AzPn), a fused system combining azulene and phenalene units, achieving an overall yield of 39.7%.

Mechanistic investigations of photochemical generation of quinone methides.

Quinone methides are important intermediates in many chemical reactions that find application in synthetic chemistry and chemical biology. They are usually formed from substituted phenol derivatives. Synthetic organic chemists have developed a variety of ways to generate quinone methides, including photochemical generation, which is usually seen as a promising way of generating desired chemical products under mild conditions and with spatial and temporal control.

Building bridges through dynamic coupling for organic phosphorescence.

Achieving long-lived room temperature phosphorescence (RTP) in organic materials has garnered significant attention in the field of optoelectronics. Although many host-guest systems with versatile performances have been developed, their photophysical mechanisms remain unclear due to the complicated intermolecular interactions and multiple energy transfer pathways, leading to unavoidable trial-and-error in molecular designs. Here we reveal that the dynamic coupling process in the excited state is crucial for inducing phosphorescence, where host and guest molecules firstly couple to enhance the intersystem crossing efficiency, and then decouple to transfer excitons to the triplet state of guest.

Enhanced hydrogen peroxide photosynthesis via charge-complementary π-electron sites.

Organic photocatalysts with porphyrin conjugated chromophore core are promising for artificial hydrogen peroxide (HO) photosynthesis, but the lack of bottom-up paradigm for oxygen (O) adsorption sites hinders their activity. Here, we introduce imidazole groups as π-electron sites with charge-complementarity to the O molecules, enhancing O binding via sub-atomically mirrored electrostatic cooperative π-π dispersion forces. In situ spectroscopy and theory reveal that the ~2 Å linear δ-δ-δ domain of the imidazole substituent exhibits 2.

Exploring diverse supramolecular tessellation through hierarchical assemblies of nonalternant nanographene.

Tessellation, as an ancient and fascinating mathematical pursuit, has not only captivated mathematicians but also has attracted chemists' increasing attention at the molecular level in recent years. Exploring tessellation at the molecular scale is pivotal for gaining profound insights into the effects of tessellation on materials and elucidating the essential design principles for supramolecular tessellation. In this study, we develop a dynamic fullerene host () with three consecutive heptagons, which promotes diverse supramolecular tessellation via hierarchical assembly.

Rational Design and Reaction Mechanism Study of the Photochemical Rearrangement of Fulvene Derivatives.

Photochemistry is considered one of the most efficient and reproducible techniques in organic synthesis. Recently, List and co-workers reported an efficient UV light triggered photochemical synthesis of spiro[2,4]heptadiene from fulvenes with different substituents ( 2023, 62, e202303119); however, the mechanistic details remain unclear, and the intermediates have not been characterized. To facilitate the applications of this novel photochemical reaction, we theoretically designed a series of fulvene derivatives with different parent molecular skeletons for analyzing the substitution effects, and two of the representative fulvenes were synthesized for investigating the reaction mechanisms by employing time-resolved transient absorption spectroscopy (TA) experiments.

Symmetry-breaking photoinduced charge transfer state in a near-IR absorbing -linked BODIPY dimer.

The synthesis and characterization of a conformationally restrained near-IR absorbing homoleptic -linked BODIPY dye is reported. The photophysical properties have been investigated using steady-state and time-resolved femtosecond transient absorption spectroscopy. A combination of spectroscopies (steady-state absorption/emission, ultrafast transient absorption spectroscopy measurements), singlet oxygen generation quantum yields, and computational studies were conducted to evaluate the nature of the excited state of the dimer 3D compared to its monomer 3M as a control.

Dual-site Langmuir-Hinshelwood mechanism in ZnCr-LDH/NH-UIO66 heterojunction for efficient photocatalytic NO oxidation.

In this study, we developed a ZnCr-LDH/NH-UIO66 heterojunction to enhance photocatalytic NO oxidation through a dual-site Langmuir-Hinshelwood (L-H) mechanism. Nitrogen oxides (NOₓ), including NO, are hazardous environmental contaminants linked to severe air pollution issues such as haze, acid rain, and photochemical smog. The composite catalyst addresses these challenges by synergistically activating NO and O under environmentally relevant conditions, including simulated solar light, ambient temperature, and NO concentrations of 1000 ppb typical of polluted urban areas.

Revealing the excited-state mechanisms of the polymorphs of a hot exciton material.

As the investigation of high efficiency thermally activated delayed fluorescence (TADF) materials become more mature, regulating the emission properties for single organic luminescence molecules has gained increasing interest recently. Herein, the donor-acceptor compounds F-AQ comprised of fluorene and anthraquinone is reported, and it exhibits a polymorphism with muti-color emission and TADF from high-level intersystem crossing (hRISC). The photodynamics and excited-state transient species were studied by femtosecond transient absorption (fs-TA) spectroscopy.

Photogeneration and Direct Observation of a 2H-phosphirene and a Closed-shell Singlet Arylphosphenium Ion.

Phosphenium ions are highly reactive species with the formula of RR'P. Although phosphenium ions were proposed as the invaluable intermediates of various important chemical processes, the methods to generate and characterize them were very limited. In this study, a novel photoprecursor to give rise to the arylphosphenium ions, 1-(naphthalen-2-yl)phosphirane, was synthesized and investigated by femtosecond to nanosecond transient absorption spectroscopies, photoproduct analysis, and density functional theory calculations.

Exploring the molecular design principles for efficient diarylethene photoacid and photohydride generators based on the photochemical reaction mechanism.

Photoacid generators (PAGs) and photohydride generators (PHGs) are specific photolabile protecting groups that release acid and hydride, respectively. Over the past decade, great efforts have been devoted to developing novel PAGs and PHGs with advanced efficiency, among which, two of the promising candidates are diarylethene (DAE)-based PAGs and PHGs, which release acids/hydrides during photochromic electrocyclization. The release quantum yield for PAGs is acceptable, while that of PHGs is only 4.

Ultrafast Spectroscopic Investigation of the Aggregation Induced TADF from High-Level Reversed Intersystem Crossing.

The thermally activated delayed fluorescence (TADF) originating from high-level intersystem crossing (hRISC) presents great potential in realizing a more full utilization of triplet excitons. In this study, DPA-FBP and TPA-FBP were doped in a PMMA film with different weight fractions to study the effect of aggregation on the luminescence properties. As a result, the TADF feature from hRISC was only found in the 50 wt % doped film, whereas the 1 wt % doped film only shows prompt fluorescence.

Synthesis, Structures, and Chiroptical Properties of NBN-Doped Helicenes with Boron Atoms in the Inner Rims.

The precise synthesis of helicenes with topologically defined length and specific heteroatomic perturbation in the screw-like conjugated skeletons plays an emerging role in the manipulation of chiral materials. Facile, selective, and programmable routes to helicenes or heterohelicenes are highly desirable yet challenging for structure-chiroptical property relationship studies. Herein, we report the synthesis and characterization of NBN-doped helicenes with boron atoms in the inner rims, enabled by the highly regioselective one-pot borylation of rationally designed precursors with, namely, fold-in or pan-out manner.

Generation and interception of bicyclo[3.2.1]oct-2-yne: an experimental and theoretical mechanistic study.

Bicyclo[3.2.1]oct-2-yne was generated from the Fritsch-Buttenberg-Wiechell rearrangement of 2-norbornylidene carbene.

Nonstoichiometry Promoted Solventless Recrystallization of a Thick and Compact CsPbBr Film for Real-Time Dynamic X-Ray Imaging.

Inorganic CsPbBr perovskite emerges as a promising material for the development of next-generation X-ray detectors. However, the formation of a high-quality thick film of CsPbBr has been challenging due to the low solubility of its precursor and its high melting point. To address this limitation, a nonstoichiometry approach is taken that allows lower-temperature crystallization of the target perovskite under the solventless condition.

Simultaneous Photocatalytic Production of H and Acetal from Ethanol with Quantum Efficiency over 73% by Protonated Poly(heptazine imide) under Visible Light.

In this work, protonated poly(heptazine imide) (H-PHI) was obtained by adding acid to the suspension of potassium PHI (K-PHI) in ethanol. It was established that the obtained H-PHI demonstrates very high photocatalytic activity in the reaction of hydrogen formation from ethanol in the presence of Pt nanoparticles under visible light irradiation in comparison with K-PHI. This enhancement can be attributed to improved efficiency of photogenerated charge transfer to the photocatalyst's surface, where redox processes occur.

Probing the alkylidene carbene-strained alkyne equilibrium in polycyclic systems via the Fritsch-Buttenberg-Wiechell rearrangement.

Strained cycloalkynes are valuable building blocks in synthetic chemistry due to their high degree of reactivity and ability to form structurally complex scaffolds, common features of many pharmaceuticals and natural products. Alkylidene carbenes provide a pathway to the formation of strained cycloalkynes through Fritsch-Buttenberg-Wiechell rearrangements, but this strategy, like other methods of alkyne generation, is believed to depend upon a thermodynamic equilibrium that favors the alkyne over the carbene. Herein three highly strained, polycyclic alkynes, previously thought to be thermodynamically inaccessible, are generated under mild conditions and intercepted through Diels-Alder cycloaddition with a diene trapping agent.

Visualizing Triplet Energy Transfer in Organic Near-Infrared Phosphorescent Host-Guest Materials.

Limited by the energy gap law, purely organic materials with efficient near-infrared room temperature phosphorescence are rare and difficult to achieve. Additionally, the exciton transition process among different emitting species in host-guest phosphorescent materials remains elusive, presenting a significant academic challenge. Herein, using a modular nonbonding orbital-π bridge-nonbonding orbital (n-π-n) molecular design strategy, we develop a series of heavy atom-free phosphors.

Iron Corrole-Catalyzed Intramolecular Amination Reactions of Alkyl Azides. Spectroscopic Characterization and Reactivity of [Fe(Cor)(NAd)].

As nitrogen analogues of iron-oxo species, high-valent iron-imido species have attracted great interest in the past decades. Fe-alkylimido species are generally considered to be key reaction intermediates in Fe(III)-catalyzed C(sp)─H bond aminations of alkyl azides but remain underexplored. Here, it is reported that iron-corrole (Cor) complexes can catalyze a wide range of intramolecular C─H amination reactions of alkyl azides to afford a variety of 5-, 6- and 7-membered N-heterocycles, including alkaloids and natural product derivatives, with up to 3880 turnover numbers (TONs) and excellent diastereoselectivity (>99:1 d.

Different Reaction Mechanisms Triggered by the Meta Effect: Photoinduced Generation of Quinone Methides from Hydroxybiphenyl Derivatives.

A series of sterically congested quinone methides (QMs) exhibit photoinduced antiproliferative activity against some human cancer cell lines. To elucidate the structure-reactivity relationship and details of mechanisms of the photogeneration of sterically congested QMs, we chose phenylphenol derivatives - as QM precursors and investigated their photodehydration processes in aqueous solutions using ultrafast spectroscopy and theoretical computations. We found that derivatives and undergo water-mediated excited-state proton transfer (ESPT) from the phenol OH, followed by expulsion of the OH to form QMs.

Macrocyclic porphyrin photocatalysts without metal chelation: A novel pathway for complete degradation of tough halophenols with longwave visible LED light source.

Halophenols are toxic and persistent pollutants in water environments which poses harm to various organisms. Due to their high stability and long residence time, ultraviolet radiation, heavy metals and oxidizing agents have been largely adopted on treating these compounds. However, these treatment methods could pose toxicity or hazardous risks to the marine environment and plant operators.

High-level reverse intersystem crossing of charge transfer compounds: to fluoresce or not to fluoresce?

Thermally activated delayed fluorescence (TADF) has been widely applied to electroluminescent materials to take the best advantage of triplet excitons. For some materials, the TADF originates from high-level reverse intersystem crossing (hRISC), and has attracted much attention due to its high efficiency for utilizing the triplet excitons. However, reports concerning the mechanistic studies on the hRISC-TADF process and structure-property correlation are sparse.

NIR-II emissive anionic copper nanoclusters with intrinsic photoredox activity in single-electron transfer.

Ultrasmall copper nanoclusters have recently emerged as promising photocatalysts for organic synthesis, owing to their exceptional light absorption ability and large surface areas for efficient interactions with substrates. Despite significant advances in cluster-based visible-light photocatalysis, the types of organic transformations that copper nanoclusters can catalyze remain limited to date. Herein, we report a structurally well-defined anionic Cu nanocluster that emits in the second near-infrared region (NIR-II, 1000-1700 nm) after photoexcitation and can conduct single-electron transfer with fluoroalkyl iodides without the need for external ligand activation.

Sub-Band Assisted Z-Scheme for Effective Non-Sacrificial HO Photosynthesis.

Photosynthesis of HO from earth-abundant O and HO molecules offers an eco-friendly route for solar-to-chemical conversion. The persistent challenge is to tune the photo-/thermo- dynamics of a photocatalyst toward efficient electron-hole separation while maintaining an effective driving force for charge transfer. Such a case is achieved here by way of a synergetic strategy of sub-band-assisted Z-Scheme for effective HO photosynthesis via direct O reduction and HO oxidation without a sacrificial agent.