The development of sustainable solid-state emitters remains challenging because of the reliance on toxic metals, complex synthetic procedures, and non-renewable starting materials. This study demonstrates the development of solid-state emitters based on lignin, a renewable byproduct of the paper industry, and the amino acid histidine or its methyl ester through simple anti-solvent crystallization under mild conditions. The prepared materials exhibited excited-state proton transfer (ESPT)-induced fluorescence and achieved optimal performance at 0.43-0.62 mol % phenolic hydroxyl content. Notably, the lignin/histidine methyl ester emitter displayed room-temperature afterglow phosphorescence with lifetimes of up to 359 ms without requiring heavy atoms for intersystem crossing. Using powder X-ray diffraction (pXRD) and ultraviolet-visible (UV-vis) data, we postulate that the histidine methyl ester host matrix provides sufficient framework rigidity and H-aggregation to enable efficient intersystem crossing and triplet-excited-state stabilization. This work offers a sustainable strategy for tunable and renewably sourced solid-state photoluminescent materials for a variety of applications.

Dirhodium paddlewheel complexes are cornerstone catalysts in organic synthesis, yet the existence and catalytic role of bis-carbene intermediates remain contentious. Through systematic density functional theory (DFT) studies at the M06L/dgdzvp(SMD) level, we demonstrate that axial and bridging ligands critically govern the relative stability of mono- versus bis-carbene species. Central to this process is π-backdonation from the Rh-Rh π* orbital into the vacant p orbital of the carbene moiety, which facilitates charge transfer and separation. This interaction stabilizes triplet intermediates and promotes the formation of bis-carbene adducts. A fundamental electronic structure difference is identified: in mono-carbene species, two radicals are delocalized across the Rh-Rh-C framework, whereas in bis-carbene species, they localize on individual Rh─C bonds. Our findings offer a refined mechanistic understanding of dirhodium catalysis, highlighting ligand-controlled spin-state modulation and intermediate speciation as crucial determinants of selectivity in C-X functionalization and cyclization reactions.

Photosensitizer plays a pivotal role in photodynamic therapy (PDT). Nonetheless, designing a photosensitizer activated by visible light from small molecules remains a significant challenge. Here, a supramolecular self-assembly donor-acceptor cocrystal is proposed as a feasible strategy to enhance the PDT of the photosensitizer. To demonstrate this concept, Vitamin K3(VK3), a UV-responsive endogenous molecule, was selected as the acceptor, paired with tetrathiafulvalene (TTF) as the donor. TTF-VK3, as a benchmark cocrystal, were synthesized, successfully validating the capability of cocrystal engineering to extend light-responsive wavelengths of a photosensitizer. TTF-VK3 cocrystals exhibited broadened absorption achieved through ground-state charge-transfer between the donor and acceptor. Ultrafast transient absorption reveals that the charge-transfer interaction substantially diminishes ΔEST of S1→T1, giving rise to a charge-transfer triplet excited state upon excitation. This endows the cocrystals with an exceptional singlet oxygen (1O2) generation capability under visible light irradiation. The developed cocrystal photosensitizer exhibits extraordinary characteristics, including easy-to-synthesize, easy-to-tune excited-state, no chemical modification, visible light excitation, and efficient 1O2 generation. These exceptional properties are remarkably preserved even in nanocrystalline cocrystal, making them particularly suitable for outstanding antibacterial efficacy, along with the ability to induce phototriggered cell death of 4T1 cancer cells after visible-light exposure. This finding establishes an effective strategy for transforming UV-responsive endogenous molecules into visible-light-activatable photosensitizer.

The development of narrowband afterglow with small full width at half maximum (FWHM) is highly challenging due to inherent spectral broadening from triplet and solid-state emissions. Here, three hybrid materials with narrowband, long-lived, high quantum yield, and temperature-responsive dynamic afterglow are realized by doping the intrinsic narrowband thermally activated delayed fluorescent (TADF) organic fluorophores into the in situ forming robust inorganic framework by a melt-cooling treatment. These hybrid materials exhibit a small FWHM of 33 nm, color purity of about 95%, and long persistent afterglow duration of over 20 s, which show a maximum photoluminescence quantum yield of 68.1% increased about 25 times compared with counterpart guests. Intriguingly, these three hybrid materials display three distinctive narrowband luminescence behaviors: persistent TADF (pTADF), ultralong room temperature phosphorescence (URTP), and dual-color afterglow of pTADF and URTP. Through structural characterization, photophysical studies, time-resolved ultrafast spectroscopy, and theoretical calculation, this work sheds light on the regulation of turning the luminescence mechanism of afterglow materials from pTADF to dual-color afterglow to URTP. Benefiting from their facile preparation, narrowband emission, long-lived afterglow, and temperature responsiveness, we showcased their great potential in an advanced application of temperature-dependent encryption. This study provides new insights into the development of high-colored purity and high-performance afterglow materials.

Abstract Dirhodium paddlewheel complexes are widely used in C–H amination, yet whether bis-nitrene intermediates participate in catalysis remains an open question. Through systematic DFT calculations at the M06L/dgdzvp/SMD level, we show that both axial and bridging ligands exert strong control over the relative stability of mono-versus bis-nitrene species. Key to this control is π-backdonation from the Rh–Rh π orbital into the vacant p orbital of the nitrene, which stabilizes triplet intermediates and facilitates bis-nitrene formation. The electronic structures of mono- and bis-nitrenes differ in a fundamental way: spin density is distributed across the Rh–Rh–N framework in mononitrenes, whereas it becomes localized on individual Rh–N bonds in bis-nitrenes. These findings establish ligand-controlled spin-state modulation as a key determinant of intermediate speciation, providing new physical insights into dirhodium-catalyzed C–H amination.

Integrating multiple photoswitching units into a single molecule is a challenging way to achieve the manipulation of molecule geometry by selectively activating individual photoresponsive moieties. A lack of understanding from a mechanism viewpoint obstructs the advancement and realization of such systems. Herein, we construct a new hybrid ionic photoswitch (PZ-SP-MeSO4) that combines spiropyran (SP) and the ionic arylazopyrazolium (PZ) counterpart. Independent modulation of PZ (E/Z) and SP (closed/open) moieties via specific irradiation wavelengths has been achieved. The photostationary state composition (>66% Z-isomer content), fatigue resistance (>15 cycles), thermal stability of the Z-isomer (t 1/2 = 717 days in water) and pH -dependent behavior enabled PZ-SP-MeSO4 to act as a potential hybrid photoswitch for molecular logic gate application, in addition to excellent water solubility (18.4 mM). More importantly, we elucidated the wavelength-gated regulating mechanisms for PZ-SP-MeSO4: 450 nm (S1) excites E → Z isomerization primarily and 365 nm (S3) triggers the SP → MC transformation. Uniquely, upon 420 nm excitation (S2), soon after the E → Z isomerization, the relay SP → MC transformation occurs from the hot ground state species due to excess vibrational energy. The understanding of the multi-state photoswitch regulated by higher excited states in this work establishes a blueprint for designing advanced light-responsive molecules.

Reactive oxygen species (ROS) are key modulators of cellular signaling, yet their direct influence on the integrin force transmission in platelets is poorly understood. Here, we combine molecular spectroscopy with integrin tension mapping to establish a mechanistic link between singlet oxygen (1O2) generation and platelet mechanics. A series of BODIPY-based photosensitizer conjugates were synthesized and systematically characterized by steady-state absorption, emission, and lifetime studies. The iodine-substituted derivative showed the highest intersystem crossing efficiency and 1O2 quantum yield, outperforming their fluorine- and methyl-substituted counterparts. When applied to human platelets, enhanced ROS production correlated with reduced integrin forces, impaired spreading, and diminished aggregation. These findings define a direct spectroscopy-to-mechanobiology correlation, connecting the photophysical properties of ROS-generating dyes with platelet mechanotransduction. This work identifies oxidative stress as a regulator of platelet force transmission and provides a framework for designing redox-based molecular probes and therapeutic strategies.

Introducing long-range order into hydrocarbon covalent organic frameworks (COFs) remains a fundamental challenge because carbon-carbon bond-forming reactions are typically irreversible and lack effective error-correction mechanisms. Here, we demonstrate a molecular approach to enhance the crystallinity of a hydrocarbon framework. A fully hydrocarbon two-dimensional (2D) COF, HKU-50, was synthesized via reversible olefin metathesis. Polymerization of a vinylene-bearing monomer using the second-generation Grubbs catalyst initially yielded an amorphous network. Upon addition of trans-stilbene, secondary metathesis is activated, regenerating catalysts that are otherwise trapped within the growing polymer. This enables continuous bond exchange and error correction during framework formation. As a result, the system evolves toward its thermodynamically favored product, HKU-50, with long-range order. The resulting COF exhibits high thermal and chemical stability, along with enhanced photophysical properties, including red-shifted emission, prolonged fluorescence lifetime, and a 4-fold increase in photoluminescence quantum yield relative to its amorphous analogue due to its extended order. These findings demonstrate a molecular approach that actively controls the crystallinity of hydrocarbon frameworks without the use of supports or interfaces that induce partial ordering of the building units.

Although the effects of ligand interlocking on specific features of coordinated metal were first reported in 1980s', strategies to precisely control these features through structural modifications of interlocked ligands remains underdeveloped. This limitation has hindered the broader exploitation of this unique class of coordination compounds across various fields of transition metal chemistry. Through a systematic comparison and detail analysis of a series of CuI catenane complexes, we show in this work that the size of the interlocked rings and exocyclic substituents are important structural parameters that regulate the exposure of the metal coordination sphere, which also influences the coordination geometry, electronic structures, spectroscopic, photophysical and electrochemical properties, as well as thermodynamic stability, ligand exchange kinetics, and chemical reactivity of the coordinated metal. Relationship between the structural features of the catenane and the extent of these effects is also revealed. These insights not only faciliate the rational design of a new type of switchable catenane catalyst wherein the interlocked structure is preserved, but also establish new principles for leveraging the unique effects of mechanical interlocking for diverse applications involving coordination complexes.

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. Meanwhile, physical organic chemists and physical chemists have made much effort to investigate the mechanisms of photochemical generation of quinone methides in the solution phase over the past few decades. This review covers both old mechanistic studies, which used traditional physical organic methods, and recent mechanistic studies, which used ultrafast techniques, in this research topic. The use of ultrafast techniques has unraveled more photophysical and photochemical details of quinone methide photogeneration processes than that of conventional techniques.

In this study, we developed a ZnCr-LDH/NH2-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 O2 under environmentally relevant conditions, including simulated solar light, ambient temperature, and NO concentrations of 1000 ppb typical of polluted urban areas. The MOF component (NH2-UIO66) selectively adsorbs NO, while the LDH component (ZnCr-LDH) efficiently activates O2 to generate reactive oxygen species (ROS). The built-in electric field (BIEF) optimizes charge separation, enabling 71.1 % NO removal efficiency with 97.8 % nitrate selectivity, effectively suppressing toxic NO2 byproduct formation. This work provides a sustainable strategy for mitigating hazardous NO emissions in air pollution control, bridging material design with environmental remediation.

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. Such a process shows universal applicability and tunable performance, with the longest lifetime for red RTP (τP = 2.4 s) reported so far. We anticipate the present work as a starting point for more sophisticated models on excited-state dynamic behaviors within host-guest systems.

Gold (Au)-involved water photocatalysis represents a promising approach for highly efficient solar-to-H-2 conversion due to the appropriate work functions for photoelectron separation and proton reduction. However, the scarcity and high cost of gold present significant challenges for industrial-scale applications. The traditional Au nanocluster, as a co-catalyst, shows suboptimal function-to-price ratios owing to the insufficient catalytic sites. Herein, a synergistic strategy of Au-1-N-3 engineering (for maximum atomic sites exposure) and mid-band assistance (for electron-hole separation) is developed to achieve tunable photodynamics and enhance photoactivity for g-C3N4-based photocatalysis. The specially engineered coordination environment via porous and defective structure facilitates the formation of single-atomic Au-1-N-3 sites, consequently enabling a novel mid-band induced the long-lived excited state and a significant *H desorption enhancement for highly efficient proton-electron coupling. As a result, the H-2 production performance of bulky g-C3N4 is only slightly noticeable, and the Au single atoms coordinated holey g-C3-xN4 (Au-1-Ho@g-C3-xN4) shows approximate to 333% increase in H-2 production (3.2 mmol h(-1) g(cat)(-1) or 157 mmol h(-1) g(Au)(-1)) than that of Au nanocluster modified holey g-C3-xN4 (Au-n-Ho@g-C3-xN4) (0.96 mmol h(-1) g(cat)(-1)). Experimental and theoretical results reveal a prolonged lifetime of active photoelectron from ps to ns via Au-1-N-3 induced mid-band trapping process, which favors high charge mobility for electron-involved H-2 generation.

Photoswitches are the most fundamental components of photonic integrated chips. The double-bond trans-cis photoswitching molecules are the most widely studied photochromic materials, but there are still numerous challenges in exploring their ultrafast photoisomerization dynamics. Here, three azobenzene-like derivatives (azo-derivatives: azo-dipyridine (AP), azobenzene (AB) and phenylazopyridine (PAP)) were selected to investigate the factors to modify the trans-cis isomerization dynamics systemically. In the solution, the photoisomerization rate of azo-derivatives from trans to cis is positively correlated with their dipole moments and their rate order AP < AB < PAP is consistent with the energy barrier obtained by potential energy surface scanning of excited states. When these azo-derivatives are assembled into nanocrystal in the suspension solutions, their isomerization rates will all accelerate, but the rate order is completely opposite to that of the solution phase. The crystal structure and energy decomposition analysis based on force field show that the weaker the intermolecular hydrogen bonding and the stronger the π-π stacking, the more favorable it is for trans-cis isomerization of azo-derivatives. This work reveals key factors that affect the trans-cis isomerization of azo-like derivatives, the dipole moment in solution, hydrogen bonding, and π-π stacking in the crystal, providing a theoretical basis for designing novel photoswitching molecular materials.

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 (1) with three consecutive heptagons, which promotes diverse supramolecular tessellation via hierarchical assembly. In the solid state, molecule 1 arranges itself into a layered square-shaped tessellation in the crystal superstructure. Interestingly, the co-crystal structures of 1 with C60 and C70 exhibit highly ordered triangular and rhombic tessellation patterns, respectively, due to the adaptive regulation of heptagons with different curved guests, demonstrating the first series of layered tessellated framework in supramolecular fullerene chemistry. This work not only enriches the development of in-solution supramolecular tessellation but also facilitates the rational design of tessellated 2D layered molecular materials.

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 ( Angew. Chem., Int. Ed. 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. It has been found that instead of density functional theory, the second-order n-electron valence state perturbation theory is necessary to acquire reliable theoretical characterization of the fulvenes examined. Our designed fulvenes were found to undergo the photorearrangement cyclopropanation reaction on the basis of photoproduct analysis. The intermediate species involved in the intramolecular hydrogen atom transfer and cyclization processes within the photorearrangement reaction were characterized by TA spectroscopy, and the full reaction pathways were proposed. Our work not only reveals the detailed mechanism of this photorearrangement reaction but also demonstrates the significance of appropriate theoretical methods for rational molecular design.

Hydrogen sulfide removal is a crucial environmental and safety issue, but its removal mostly involves high energy consumption or the utilization of toxic chemicals. Photocatalytic oxidation is a green process for sulfide removal, but its efficiency using dispersed catalysts has been restricted by uneven light intensity. In this study, a high efficiency catalytic material was designed and synthesized for the enhanced photooxidation of sulfide to elemental sulfur. 5,10,15,20-Tetrakis(p-carboxylphenyl)porphyrin (4-Car-PP) associated with transition metal ions was confined on bacterial cellulose (BC) as a hydrogel and operated under visible light with microaeration. Nickel was identified as the most efficient catalyst, and BC could significantly improve its photocatalytic process. Compared to Ni-Car-PP alone, sulfur recovery increased from 0.14 to 20.1 mmol dm-3 h-1 with the BC-Ni-Car-PP hydrogel. Light also showed a 4.3-fold enhancement in elemental sulfur fixation. Transient adsorption study revealed that the chelation of sulfide on the nickel center facilitated singlet state photoexcited electron transfer, which enhanced electron transfer through the metal-ligand cooperative effect. This limited polyoxosulfur ion formation but facilitated polysulfide formation, leading to an increase in elemental sulfur formation. The combination of the hydrogel catalyst, microaeration, and mild operational requirements implies its potential application in air pollution control, biogas purification, and wastewater management without the need for sophisticated pH control and regulations.

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. As a result, an unambiguous signal of through space charge transfer (TSCT) was observed in the fs-TA spectra of the crystal with the π-π interaction between the fluorene and anthraquinone groups, whereas the other amorphous solids and crystal only show a conventional deactivation pathway of hRISC-TADF. In this study, we successfully realize the direct observation of the morphism-dependent TSCT in a crystal, which provides the observations in solid-state ultrafast excited-state dynamics and deepens the insight into the design of potential mechanochromic materials and thermochromic utilization of the polymorphism of organic luminescence molecules. There is interest in hot exciton materials with multi-colour emission from solid states of single organic luminescent molecules. Here, the authors report on polymorph dependent differences in emission properties and excited-state behaviours.