Precise multi-stimuli regulation of intramolecular charge-transfer (CT) states in mechanically interlocked systems is challenging due to the complexities of synergistic control and unresolved ultrafast dynamics. We report a triple-stimuli strategy to modulate CT states in a [3]rotaxane by controlling solvent polarity, anion-induced macrocycle translocation, and aggregation, thereby regulating the vibrational freedom of the central 9,10-distyrylanthracene (DSA) chromophore. Spectroscopy studies show that increased solvent polarity shortens the CT-state lifetime and enhances non-radiative decay, thereby quenching fluorescence. In contrast, aggregation induces a blue-shift in emission, enhances intensity, and prolongs the CT-state lifetime, consistent with aggregation-induced emission (AIE). Anion binding triggers macrocycle movement, releasing steric constraints to tune the lifetime to an intermediate value. This work elucidates a supramolecular steric-electronic regulatory mechanism and offers design principles for stimuli-responsive optical materials.

The distinct architectures in macrocyclic molecules allow them to fulfil the specialized roles as important molecular containers or recognition sites. However, the impact of macrocyclization on the excited states of the molecular building blocks that construct the macrocycles is yet to be understood. Herein, the electronic structures and excited-state dynamics of pillar[4]arene[1]quinone (P4Q1) were compared with those of the 2,5-dimethylquinone reference molecule through steady-state and time-resolved transient absorption spectroscopic investigations and quantum chemical computations. The macrocyclic skeleton is shown to facilitate the formation of a set of low-lying intramolecular charge transfer excited states in the photoexcited P4Q1, leading to the tremendous suppression of intersystem crossing via a conical intersection mechanism and causing a significantly reduced triplet excited-state yield. Furthermore, the solvation dynamics was also explored as a function of the host-guest interactions between P4Q1 macrocycles and polar acetonitrile molecules, revealing the negligible influence of the acetonitrile guest molecule encapsulated inside the cavity. These results provide guidance to understand the excited-state dynamics of important supramolecular macrocycles and the related photochemical processes.

Exploring the solvatochromic processes of carbon dots (C-dots) is significant for both fundamental science and their corresponding applications. At present, there are a few relevant concerns, such as the exact solvatochromic photophysical picture and positive and negative solvatochromism versus the composition and structure of C-dots, which have remained open questions. Herein, by our group's adequate separation/purification technique based on systematic investigation, four kinds of highly purified C-dots are isolated and obtained. Through quantitative analysis and comparison, we find that the solvatochromic behaviors of C-dots result from their intrinsic charge distribution. Only if the C-dots have a donor-π-acceptor configuration can they exhibit distinct solvatochromism through "intramolecular" charge transfer effects; furthermore, the direction and magnitude of the absorption/fluorescence band shift of the C-dots in different (high- and low-polarity and aprotic and protic) media are dependent on the ratios of the acceptors to donors. In contrast, for the C-dots with the donor-π or acceptor-π configuration, negligible solvatochromic behaviors are observed due to insufficient charge transfer within the corresponding particles.

Polycyclic aromatic quinones (PAQs) are environmental pollutants that induce oxidative stress in biological systems. This study investigates the photochemical interactions of two representative polycyclic aromatic quinones, phenanthrene-9,10-quinone and acenaphthoquinone, with glutathione using transient absorption spectroscopy and DFT calculations. Frontier orbital analysis suggests hydrogen atom transfer (HAT) is the favored pathway. Experimentally, photoexcited acenaphthoquinone undergoes efficient HAT with glutathione (k(q) = 0.35 & times; 10(9) M-1 s(-1)), whereas triplet state phenanthrene-9,10-quinone shows no significant reactivity. Site-specific studies identify the cysteine thiol group as the exclusive reaction site. Although HAT is thermodynamically feasible for both systems (Delta G < 0), the inactivity of phenanthrene-9,10-quinone/glutathione is attributed to steric hindrance. These findings deepen our molecular-level understanding of how PAQs interact with key biological antioxidants.

Fluorescent nucleobase analogs (FBAs) are valuable tools for studying nucleic acid structure and dynamics. However, their utility is often limited by substantial fluorescence quenching upon incorporation into oligonucleotides and variable brightness influenced by neighboring bases. In this study, we present a novel turn-on nucleoside, 3b, a thiazolyl-dU analog (hereinafter referred as TzdU), engineered to overcome these limitations and enable reliable DNA fluorescence imaging. Compared to its nearly nonfluorescent free form, TzdU shows approximately a 10-fold increase in brightness in single-stranded DNA (ssDNA) and up to a 50-fold enhancement in double-stranded DNA (dsDNA). Importantly, it maintains relatively stable brightness regardless of surrounding bases by evading common quenching pathways, including solvent-induced collisional quenching and excited-state proton transfer (ESPT). The triphosphate derivative of TzdU is efficiently utilized by various DNA polymerases, including Deep Vent and KOD XL, facilitating real-time, intensity-based monitoring of critical enzymatic processes such as PCR and primer extension without external labels. Furthermore, TzdU can illuminate DNA in a gradient manner, enabling the visualization and encryption of information. As the first FBA to achieve universal turn-on characteristics, sequence insensitivity, and compatibility with enzymatic reactions, TzdU serves as a novel tool for investigating nucleic acid dynamics and advancing fluorescence-based methodologies.

Abstract Coordination-driven self-assembly enables the construction of discrete supramolecular coordination complexes (SCCs) with well-defined geometries, but metallacycles showing multicolor or white-light emission via ligand excited-state modulation remain rare. Here, we report a multicolor photoluminescent metallacycle M assembled from a triphenylamine-based dipyridine ligand L1 and a benzothiadiazole-based diplatinum(II) ligand L2. M exhibits solvatochromic fluorescence, appearing purple in toluene, white in ethyl acetate and THF, and red in DMSO. Femtosecond transient absorption spectroscopy reveals the multicolor luminescence mechanism. For L1, the relaxation pathway shifts from a locally excited state to charge-transfer (CT) states with increasing solvent polarity, while L2 undergoes ultrafast intersystem crossing to a long-lived triplet state. Within M, coordination-induced metal-to-ligand charge transfer (MLCT) suppresses fluorescence resonance energy transfer (FRET) between L1 and L2, enabling multicolor emission. This work provides a new strategy for constructing multicolor and white-light-emitting metallacycles, with promising applications in optoelectronics and bioimaging.

Abstract Atomically precise clusters exhibit significant promise in photocatalysis, while the precise and controllable synthesis of metal nanoclusters with well-defined active sites for enhanced catalytic performance remains a critical challenge. In this study, we synthesized a series of [Cu4Pt2(R-PhC≡C)4(dppy)4]2+ clusters (dppy = diphenyl-2-pyridylphosphine; R = CH3O, F, or CF3) and abbreviated them as R–Cu4Pt2 (R = CH3O, F, or CF3) for brevity. The R–Cu4Pt2 clusters were respectively immobilized on the surface of CdS nanorods, yielding a series of R–Cu4Pt2/CdS composite photocatalysts for the efficient and selective dehydrocoupling of amines with hydrogen (H2) evolution. Experimental results demonstrated that the introduction of clusters not only significantly enhanced the selectivity of benzylamine C–C bond formation but also improved the reaction yield. Moreover, ligand effects regulated the catalytic activity by altering the reaction microenvironment around the Cu4Pt2 core metal center, leading to distinct photocatalytic H2 evolution rates following the order of R groups: CF3– > F– > MeO–. Density functional theory (DFT) calculations elucidated the radical–radical coupling mechanism for synthesizing the C–C-coupled vicinal diamines. It also revealed that the R substituent in R–Cu4Pt2 exhibits varying electron-withdrawing ability, which modulates the electronic structure of the catalytic center and the proton activation barrier for H2 evolution, thereby resulting in controllable photocatalytic activities. This work enables precise tuning of the photocatalytic performance in cluster-based photocatalysts by rationally employing substituent effects to modulate the active-site microenvironment.

ABSTRACT Developing multicolor‐tunable semiconductors is critical for next‐generation displays. Up to date, achieving the color tunability within a fixed‐composition material without employing any doping strategy remains a persistent scientific challenge. Herein, we demonstrate an innovative and facile method to attain a dual‐color emission function in a single Dion‐Jacobson (D‐J) perovskite microcrystal (MC) via the lattice strain engineering, which artificially introduces deep‐level defects as radiative centers. The rich and reversible color tuning from cyan to pink are accomplished via a precise control of the intrinsic excitonic to deep‐level defect luminescence balance by adjusting either the incident power or repetition rate of the excitation laser source. These findings pioneer a novel approach to the color modulations in a single‐crystal structure, establishing 2D perovskites as highly promising candidates for future display technologies.

The simultaneous utilization of photoelectrons and holes to achieve the coupling of photocatalytic hydrogen evolution with the selective oxidation of organic substances holds significant importance. Yet, this strategy is often constrained by the inadequate charge separation efficiency of photocatalysts and the scarcity of sufficient catalytic active sites. Herein, a conductive bimetallic metal-organic framework (MOF), CuxNi1-x-HHTP, was strategically integrated onto the surface of CdS nanorods, yielding a visible-light-responsive CdS@CuxNi1-x-HHTP core-shell inorganic-organic hybrid, which demonstrated exceptional performance and remarkable product selectivity in the photocatalytic dehydrogenative coupling of benzylamine. The incorporation of CuxNi1-x-HHTP endows the photocatalytic system with a plethora of accessible reactive sites. Moreover, the ultrafast spectroscopy research unveils that Cu0.5Ni0.5-HHTP exhibits robust capability for efficient photogenerated electron extraction, thereby effectively facilitating the spatial separation of photogenerated carriers during the photocatalytic process. Notably, when the CdS/Cu0.5Ni0.5-HHTP molar ratio was 1:2 in photocatalysts, the catalyst denoted as CdS@Cu0.5Ni0.5-HHTP-2 demonstrated a remarkable hydrogen evolution rate of 29.79 mmol g- 1 h- 1, accompanied by a benzylamine conversion rate of 58.39%, while maintaining high stability. This study introduces a strategy for integrating conductive bimetallic metal-organic frameworks with inorganic semiconductors, enabling ultrafast photocarrier transfer and significantly enhancing photocatalytic efficiency.

Metal halide perovskites (MHPs) inherently feature soft ionic lattices, endowing their crystal structures with high sensitivity to both temperature and pressure. It has been well established that the lowering of temperature under atmospheric pressure induces phase shift in the typical CH3NH3PbI3 (MAPbI3) perovskites from tetragonal to orthorhombic structures, leading to a decreasing photovoltaic efficiency due to the poorer charge transport performance. Herein, we report an investigation into the synergistic effects of vacuum and temperatures on phase transition and charge transport dynamics of MHPs, which is designed to simulate the outer space environments with intrinsic temperature cycling and high vacuum. Surprisingly, we find that MAPbI3 under high vacuum exhibits an unusual compression behavior during phase transitions and remains in the tetragonal phase even around 78 K. This phase stability is attributed to a substantial drop in thermal expansion coefficient under low pressure. The material achieves a superior carrier diffusion length (10.2-14.9 μm) in the simulated space environment, surpassing its performance in terrestrial settings. These results provide new insight into the structural stability of perovskites and highlight their applicability across various conditions.

Metal nanoparticles include molecular nanoclusters and metallic nanocrystals. Investigating the critical transition sizes from nanoclusters to nanocrystals is appealing. However, achieving precise size control near the critical size region remains challenging, especially for not-so-noble metal nanoparticles (Ag, Cu etc.). Herein, we introduced an active metal anti-galvanic doping strategy to resolve both stability and multi-dispersity issues and demonstrated the gram-scale synthesis (2.40 g of crystals, more than 200 times the existing crystal output record for over 100-metal-atom nanoparticles) of a 1796-atom Ag-Zn nanoparticle. Furthermore, we successfully de-alloyed the Ag-Zn nanoparticles with the remaining structure essentially unchanged via a ligand-exchange method, obtaining 1.03 g of mono-Ag nanoparticle crystals in a one-pot reaction. Such a surgery-like de-alloying was not previously reported. Both of the as-obtained nanoparticles exhibit penta-twinned face-centered cubic (fcc) structures with well-defined shape-number arrangements and display plasmon-like absorptions yet exist in molecular states, as evidenced by ultrafast dynamics measurements. Furthermore, crystallization-induced photothermal enhancement and size-dependent absorbance were observed.

Triplet-triplet energy transfer (TTET) via the Dexter mechanism is central to many photochemical applications, yet a quantitative structure-kinetic relationship for bimolecular quenching rate constants (kq) is still lacking. Here, using two photosensitizers and a series of anthracene-based acceptors with tailored steric profiles, we systematically investigate how nonconjugated substituents regulate kq. The most significant results are when the triplet energy gap exceeds ∼0.2 eV, kq is governed solely by steric hindrance and the suppression originates from spin-density-free units that block donor-acceptor wave function overlap. We establish a quantitative model in which the effective collision probability η equals the product of the van der Waals surface fractions carrying triplet spin density (P) for both donor and acceptor, giving kq,calc = kdiffuse × η. Predicted rates match experimental values well and are further validated against literature systems.

The design of photosensitizers that can generate ·OH from water as well as efficient charge separation (CS) is integral to the hypoxic tumor photodynamic therapy (PDT). However, such ·OH photo-generators are scarcely reported, let alone those based on a simple D-π-A scaffold. Herein, we highlight the ·OH photo-generators TPESPyCx@BSA based on a co-assembly strategy to initiate the photocatalysis of water oxidation into ·OH as well as the efficient charge-separation for oxygen-independent PDT. The TPESPyCx@BSA were constructed by the co-assembly of a series of simple D-π-A scaffold tetraphenylpyridine salt TPESPyCx with BSA. The high-efficiency generation of ·OH was confirmed by the EPR trapping technique, and the isotope tracing experiments revealed that the oxygen source of ·OH generation originated exclusively from the H2O. The calculated VB potential of TPESPyCx@BSA met the thermodynamic conditions of ·OH produced by the oxidation of water. Deciphered by the transient absorbance spectra, the charge separation state was realized after the co-assembly, which guaranteed the electron transfer to generate ·OH following the oxygen-independent pathway. TPESPyCx@BSA exhibited superb photocytotoxicity even under severe anoxic conditions and excellent antitumor efficacy on in vivo mouse models. This work provides a strategy for constructing oxygen-independent photodynamic agents, which opens up an avenue for effective PDT against hypoxic tumors.

The design of NIR‐I activated oxygen‐independent photosensitizers with optimal delivery efficiency holds great promise in efficient photodynamic therapy of deep‐seated hypoxic tumors. Herein, by fabricating intratumoral synthetic therapeutic system, the silenced prodrug AICST are selectively and spontaneously transformed into AICST‐SO 3 with NIR‐I absorption, which underwent oxygen‐free photo‐redox cycle for hypoxic tumor phototherapy. The prodrug AICST based on D‐π‐A structure with a two‐photon moiety coumarin as donor (D), C═C bond as π bridge, and indole derivative as electron acceptor (A) responded to the intracellular overexpressed SO 3 2− to yield photosensitizer AICST‐SO 3 . The photo‐excited AICST‐SO 3 generated charge separation species, wherein the strong oxidized moiety would capture electron from water to generate cytotoxic hydroxyl radical (OH•), and the anionic radicals transferred electrons to pyruvic acid to accomplish the photo‐redox cycle. In vitro cellular experiments confirmed the intracellular synthesis of AICST‐SO 3 and the efficient cancer cells killing capability. In vivo mouse model experiments revealed that, under the 800 nm irradiation, the tumor can almost be completely ablated by the prodrug AICST , further confirming the great advance of the intratumoral synthetic therapeutic system activated by NIR‐I light for hypoxic tumor therapy. This work offers new pathway for developing a potent phototherapy model.

A novel square-shaped metallacycle M, functionalized with carbazole and benzothiadiazole, was synthesized through coordination-driven self-assembly. The discrete metallacyclic architecture endows M with superior optical properties owing to its rigid metallacyclic skeleton and donor-acceptor electronic structure. The femtosecond transient absorption (fs-TA) spectroscopic measurements demonstrated that the macrocyclic skeleton significantly promotes the intramolecular charge transfer efficiency and the rapid formation of triplet states. Furthermore, leveraging M as a photocatalyst enabled to drive the cross-dehydrogenative coupling (CDC) reactions with >90% efficiency, which was facilitated by its persistent charge separation states and long-lived triplet states. This work highlights the critical role of metallacycle engineering in optimizing photophysical dynamics and advancing applications in smart optoelectronics and sustainable photocatalysis.

Selectively transforming the non-radiative pathway of excited-state photosensitizers (PSs) into radiative and intersystem crossing (ISC) processes is crucial for fluorescence imaging-guided photodynamic therapy (PDT). Herein, human serum albumin (HSA), with abundant amino acid residues, was co-assembled with anion-pi+ PSs (An-O, AnS-O, and AnSS-O) to create PSs-albumin complexes (An-O@HSA, AnS-O@HSA, and AnSS-O@HSA), resulting in promoted biocompatibility and colloidal stability. Both in vitro and in vivo assessments demonstrated that AnSS-O@HSA exhibited the highest-performance fluorescence emission and superoxide anion (O2-center dot) generation capacity, which can effectively induce enhanced apoptosis in HepG2 cells. In-depth mechanistic investigations revealed that HSA, functioning as a boosting agent, could effectively suppress nonradiative decay channels and prolong the triplet state lifetime of PSs. Additionally, HSA can also serve as an electronic reservoir, augmenting its photocurrent response, which further promoted the fluorescence imaging-guided PDT. This study presented a facile strategy for controlling the energy dissipation pathways in the excited state of PSs.

ABSTRACT Surface co‐catalyst modification is a feasible strategy to boost photocatalytic activity. However, it usually meets the issue of limited contact area and poor interfacial interaction, which greatly affects the interfacial charge transfer efficiency. Herein, a self‐adaptive partially oxidised W‐based quantum dot (WQDs) is designed to boost the photocatalytic performance of Bi 12 O 17 Br 2 . Because of the formation of the strong coupled interface, the BiS 1 O 4 site can be created with a local interfacial asymmetric configuration. This BiS 1 O 4 site can serve as an axial polarisation centre to drive rapid interfacial charge transport from Bi 12 O 17 Br 2 to WQDs via the formed Bi‐S bond. At the same time, the partially oxidised WQDs supply a higher charge aggregate state, favouring the small molecule coordination and activation. Benefiting from these features, the greatly improved photocatalytic performance can be achieved for WQDs/Bi 12 O 17 Br 2 . This work offers a feasible approach for designing a self‐adaptive partially oxidised quantum dot cocatalyst to build a strong coupled interfacial asymmetric configuration to optimise photocatalytic activity.

The sensitization-initiated electron transfer (SenI-ET) mechanism is a well-established concept in photoredox catalysis, yet its kinetic intricacies remain to be fully elucidated. In this study, we have successfully designed and synthesized a dyad, Ru(bpy)3 2+-pyrene (Ru-Py), which functions dually as a sensitizer and a reductant. By the use of the rapid intramolecular triplet and singlet energy transfer of Ru-Py, the complex decay pathway of the SenI-ET process was effectively simplified. Notably, we have demonstrated that direct electron transfer from 3Ru*-Py to diisopropyl ethylamine generates Ru(I)-Py, which further drives the catalytic process, rather than the catalytic reaction being driven by the formation of a Ru-Py center dot- through electron transfer from Ru-3Py* to diisopropyl ethylamine. Furthermore, we employed Ru-Py as a catalyst for the C-H oxidation of an activated aryl bromide, demonstrating superior catalytic efficiency compared to that of the conventional Ru(bpy)3 2+/pyrene system.

Attenuated fluorescence of organic fluorescent probes is typically observed in hydrophilic environments due to solvatochromic fluorescence quenching, where the brightness decreases along with increasing solvent polarity. However, strategies to overcome this challenge remains elusive. Herein, we report polarity-facilitated anti-solvatochromic fluorescence enhancement, i.e., the emission becoming stronger in solvents with higher polarity, of two novel donor-acceptor type fluorescent probes. Using the femtosecond (nanosecond) UV/vis pump-broadband probe spectroscopy combined with density function theory calculations, we investigate the excited-state dynamics of these fluorescent probes as a function of solvent polarity. The femtosecond transient absorption spectra reveal an initial hypsochromic shift of the excited-state absorption signature, immediately after excitation, indicating rapid stabilization of the lowest excited state through dipole-dipole interactions. The gradual ground-state recovery is accompanied by the formation of a new persistive excited-state absorption signature suggesting the competition between fluorescent recombination and intersystem crossing (ISC). Our TDDFT calculations suggest that a rare S1-T2 intersystem crossing is inhibited by solvent polarity, prolonging the S1 lifetime and thereby preventing the solvatochromic fluorescence quenching. This study provides new insights into the ISC-mediated fluorescence enhancement, offering potentials for investigating polarity-sensitive chemical and biological processes.