Intermolecular Research Articles

Methyl side-groups control the Ia3̄d phase in core-non-symmetric aryloyl-hydrazine-based molecules.

Control of the formation of liquid crystalline Ia3̄d gyroid phases and their nanostructures is critical to advance materials chemistry based on the structural feature of three-dimensional helical networks. Here, we present that introducing methyl side-group(s) and slight non-symmetry into aryloyl-hydrazine-based molecules is unexpectedly crucial for their formation and can be a new design strategy through tuning intermolecular interactions: the two chemical modifications in the core portion of the chain-core-chain type molecules effectively lower and extend the Ia3̄d phase temperature ranges with the increased twist angle between neighboring molecules along the network. The detailed analyses of the aggregation structure revealed the change in the core assembly mode from the double-layered core mode of the mother molecule (without methyl groups) to the single-layered core mode. Such changes are explained in terms of modified intermolecular interactions in those phases employing quantum chemical calculations.

MutualDTA: An Interpretable Drug-Target Affinity Prediction Model Leveraging Pretrained Models and Mutual Attention.

Efficient and accurate drug-target affinity (DTA) prediction can significantly accelerate the drug development process. Recently, deep learning models have been widely applied to DTA prediction and have achieved notable success. However, existing methods often encounter several common issues: first, the data representations lack sufficient information; second, the extracted features are not comprehensive; and third, most methods lack interpretability when modeling drug-target binding. To overcome the above-mentioned problems, we propose an interpretable deep learning model called MutualDTA for predicting DTA. MutualDTA leverages the power of pretrained models to obtain accurate representations of drugs and targets. It also employs well-designed modules to extract hidden features from these representations. Furthermore, the interpretability of MutualDTA is realized by the Mutual-Attention module, which (i) establishes relationships between drugs and proteins from the perspective of intermolecular interactions between drug atoms and protein amino acid residues and (ii) allows MutualDTA to capture the binding sites based on attention scores. The test results on two benchmark data sets show that MutualDTA achieves the best performance compared to the 12 state-of-the-art models. Attention visualization experiments show that MutualDTA can capture partial interaction sites, which not only helps drug developers reduce the search space for binding sites, but also demonstrates the interpretability of MutualDTA. Finally, the trained MutualDTA is applied to screen high-affinity drug screens targeting Alzheimer's disease (AD)-related proteins, and the screened drugs are partially present in the anti-AD drug library. These results demonstrate the reliability of MutualDTA in drug development.

Symmetry Breaking: Case Studies with Organic Cage-Racemates.

ConspectusSymmetry is a pervasive phenomenon spanning diverse fields, from art and architecture to mathematics and science. In the scientific realms, symmetry reveals fundamental laws, while symmetry breaking─the collapse of certain symmetry─is the underlying cause of phenomena. Research on symmetry and symmetry breaking consistently provides valuable insights across disciplines, from parity violation in physics to the origin of homochirality in biology. Chemistry is particularly rich in symmetry breaking studies, encompassing areas such as asymmetric synthesis, chiral resolution, chiral structure assembly, and so on. Across different disciplines, a well-defined methodology is fundamental and necessary to analyze the symmetry or symmetry breaking nature behind the phenomenon, enabling researchers to uncover the underlying principles and mechanisms. Basically, three key points underpin symmetry-related research: the scale-dependency of symmetry/symmetry breaking, the driving force behind symmetry breaking phenomena, and the properties arising from symmetry breaking.This Account will focus on the three aforementioned key points elucidated with organic cages as proof-of-concept models, as organic cages exhibit shape-persistent 3D molecular frameworks, well-defined molecular motion, and a high propensity for crystallization.First, we examine racemization processes of organic cages with dynamic molecular motions to illustrate that symmetry and symmetry breaking are time-scale-dependent. Specifically, the racemization, driven by molecular motion, is influenced by hydrogen bonding and the rigidity of the cage framework, which may or may not be observable within the experimental temporal scale. This determines whether the enantiomeric excess system, namely, the symmetry broken system, can be detected experimentally. We also investigate the hierarchical structures self-assembled by racemic organic cages, demonstrating that symmetry and asymmetry manifest differently across spatial scales, from molecular to supramolecular and macroscopic levels. Second, we discuss the driving force behind spontaneous chiral resolution─a classic symmetry-breaking event during crystallization─from a thermodynamic perspective. We suggest that racemic compounds, compared to conglomerates, are more entropy-favored, explaining their greater prevalence in nature. Spontaneous chiral resolution can take place only when a favorable enthalpy compensates for unfavorable entropy. In conglomerates composed of organic cages, strong intermolecular interactions along the screw axes provide the necessary compensation. Finally, we explore the unique properties that emerge from symmetry-broken molecular packing within crystals of cage racemates, such as second-harmonic generation and piezoelectricity. It turns out that the symmetry operation in molecular packing plays a critical role in determining material properties. By comprehensively analyzing symmetry and symmetry-breaking in organic cage racemates, this Account provides insights into symmetry-related phenomena across scientific disciplines. It also paves the way for designing novel materials with tailored properties for applications in optics, electronics, and beyond.

Competing addition processes give distinct growth regimes in the assembly of 1D filaments.

We present a model to describe the concentration-dependent growth of protein filaments. Our model contains two states, a low entropy/high affinity ordered state and a high entropy/low affinity disordered state. Consistent with experiments, our model shows a diffusion-limited linear growth regime at low concentration, followed by a concentration-independent plateau at intermediate concentrations, and rapid disordered precipitation at the highest concentrations. We show that growth in the linear and plateau regions is the result of two processes that compete amid the rapid binding and unbinding of non-specific states. The first process is the addition of ordered molecules during periods in which the end of the filament is free of incorrectly bound molecules. The second process is the capture of defects, which occurs when consecutive ordered additions occur on top of incorrectly bound molecules. We show that a key molecular property is the probability that a diffusive collision results in a correctly bound state. Small values of this probability suppress the defect capture growth mode, resulting in a plateau in the growth rate when incorrectly bound molecules become common enough to poison ordered growth. We show that conditions that non-specifically suppress or enhance intermolecular interactions, such as the addition of depletants or osmolytes, have opposite effects on the growth rate in the linear and plateau regimes. In the linear regime, stronger interactions promote growth by reducing dissolution events, but in the plateau regime stronger interactions inhibit growth by stabilizing incorrectly bound molecules.

From X- To J-Aggregation: Subtly Managing Intermolecular Interactions for Superior Phototheranostics with Precise 1064 nm Excitation.

The stacking mode in aggregate state results from a delicate balance of supramolecular interactions, which closely affects the optoelectronic properties of organic π-conjugated systems. Then, managing these interactions is crucial for advancing phototheranostics, yet remains challenging. A subtle strategy involving peripheral phenyl groups is debuted herein to transform X-aggregated SQ-H into J-aggregated SQ-Ph, reorienting intermolecular dipole interactions while rationally modulating π-π interactions. Co-assembled with liposomes (DSPE-PEG2000), SQ-Ph nanoparticles (NPs) exhibit low toxicity, superior biocompatibility, and a bathochromic shift to the 1064nm match-excited NIR-II region, with a fluorescence brightness (ε1064nm ΦNIR-II) of 4129M-1 cm-1 and a photothermal conversion efficiency (PCE) of 48.3%. Preliminary in vivo experiments demonstrate that SQ-Ph NPs achieve a signal-to-background ratio (SBR) of up to 14.29 in NIR-II fluorescence imaging (FLI), enabling highly efficient photothermal therapy (PTT) of tumors guided by combined photoacoustic imaging (PAI). This study not only enriches the J-aggregation library but also provides a paradigm for optimizing photosensitizers at the supramolecular level.

Controlling pseudopolymorphism via robust and repetitive solvent-containing supramolecular interactions in urea-based isostructural coordination polymers.

In a systematic study, six pseudopolymorphic coordination polymers containing the ditopic 1,3-di(pyridin-4-yl)urea ligand (4bpu) constructed with d10 metal cations, possessing the formula {[M(4bpu)I2]S}n [(M = Zn, Cd and Hg), (S = MeOH or EtOH)], namely Zn-MeOH, Zn-EtOH, Cd-MeOH, Cd-EtOH, Hg-MeOH and Hg-EtOH were obtained. The title compounds were characterized by single-crystal X-ray diffraction analysis (SC-XRD), elemental analysis (CHN), FT-IR spectroscopy, thermogravimetric analysis (TGA), and powder X-ray diffraction (PXRD). The diffraction studies show that these compounds are isostructural 1D zig-zag chain coordination polymers which is also confirmed using XPac 2.0.2 software and the occurrence of three- and one-dimensional (3D and 1D) isostructurality was investigated in terms of their molecular assembly in solid state structures. These comparisons were performed by extracting the dissimilarity index and stretching parameters, providing quantitative insights into the structural similarity across the pseudopolymorphic coordination polymers, which exhibit robust 3D isostructurality. Additionally, the geometry of the zig-zag chain structures was thoroughly analyzed, highlighting the subtle variations and common features that contribute to isostructurality. The supramolecular architecture of these pseudopolymorphs is stabilized by robust and repetitive hydrogen bonding motifs involving N-H⋯O, O-H⋯I and C-H⋯I interactions between the framework and guest solvent molecules (MeOH or EtOH). These interactions replace the commonly observed bifurcated hydrogen bonds (α-tape motif) between urea moieties, emphasizing the pivotal role of solvent molecules in controlling pseudopolymorphism and defining the final structural assembly. This detailed understanding of hydrogen bonding provides valuable insights into tailoring intermolecular interactions, enabling the design of materials with enhanced functionalities for diverse applications. A detailed investigation of urea-CO⋯πpy interactions in urea-based compounds highlights the classification of these interactions as semilocalized (η2-SL) based on geometric parameters and reveals their significance through crystallographic and database studies. Hirshfeld surface analysis has been performed for all compounds to determine the percentage contribution of intermolecular interactions.

Monolayer MoS2 with S vacancy defects doped with Group V non-metallic elements (N, P, As): a first-principles study.

This study systematically investigated the effects of single S-atom vacancy defects and composite defects (vacancy combined with doping) on the properties of MoS2 using density functional theory. The results revealed that N-doped S-vacancy MoS2 has the smallest composite defect formation energy, indicating its highest stability. Doping maintained the direct band gap characteristic, with shifts in the valence band top. The Fermi level slightly shifted down in N- and P-doped systems, with N-doped MoS2 showing a larger increase in valence band top energy. Doping also significantly altered the density of states at the Fermi level and weakened the dielectric properties of MoS2. The maximum dielectric peaks of doped systems appeared near 2.7 eV with reduced intensities and red-shifted energies. Optical properties were significantly changed, with decreased reflectance, narrower reflectance spectra, and blue-shifted absorption spectra. These findings suggest that introducing composite defects can effectively reduce the forbidden bandwidth of MoS2, enhancing electrical conductivity. This research provides theoretical guidance for novel material design and offers insights into composite defect behavior in other two-dimensional materials. The Materials-Studio CASTEP module was used to calculate density functional theory (DFT). A plane wave ultrasoft pseudopotential is used to optimize the crystal structure, and the generalized gradient approximation (GGA) in the form of Perdew-Burke-Ernzerhof (PBE) is used to characterize the exchange correlation energy. After the convergence test, the truncation energy and dot settings were finally selected to be 450 eV and 3 × 3 × 1, respectively, the convergence accuracy was set to 1.0e-5eV/atom, and the convergence criterion for the interatomic interaction force was 0.02 eV/Å. The parameters were all at or better than the accuracy settings. The vacuum layer between the layers wasset to 18 Å to avoid interactions caused by the periodic calculation method.

Controlled Self-assembly of Nanographdiynes Mediated by Molecular Dipoles Induced by Rotatory Asymmetric Substituents.

The discrete π- stacks of specific lengths and orientation is crucial for understanding the impact of intermolecular interactions on optical or electronic properties of nanographdiynes. We designed and synthesized nanographdiynes modified with bulky rotatable asymmetric substituents. The peripheral substituents with different push-pull electronic properties can induce molecular dipoles perpendicular to nanoGDY π surface with different orientation. Mediated by directional dipole-dipole interactions, o-TBGDY substituted with electron-donating tert-butylphenyl groups cofacially dimerized with a twist angle, involving intermolecular interlocking of ortho-substituted tert-butylphenyl groups. In contrast, OTFGDY substituted with electron-withdrawing trifluorophenyl groups formed dimeric H-aggregates with an in-plane shift along one diyne linkage, in which the ortho-substituted trifluorophenyl groups point toward the outside of the interacting π-plane. o-TBGDY can only exist as isolated H-dimer in the solid state, while OTFGDY can form a hybrid tetramer of H- and J-aggregates. Our researches reveal a new method for preparing discrete π-stacked dye assemblies with well-defined optoelectronic properties.

Quantification Method of Driving Risks for Networked Autonomous Vehicles Based on Molecular Potential Fields

Connected autonomous vehicles (CAVs) face constraints from multiple traffic elements, such as the vehicle, road, and environmental factors. Accurately quantifying the vehicle’s operational status and driving risk level in complex traffic scenarios is crucial for enhancing the efficiency and safety of connected autonomous driving. To continuously and dynamically quantify the driving risks faced by CAVs in the road environment—arising from the front, rear, and lateral directions—this study focused s on the self-driving particle characteristics that enable CAVs to perceive their surrounding environment and make driving decisions. The vehicle-to-vehicle interaction behavior was analogized to the inter-molecular interaction relationship, and a molecular Morse potential model was applied, coupled with the vehicle dynamics theory. This approach considers the safety margin and the specificity of driving styles. A multi-layer decoder–encoder long short-term memory (LSTM) network was employed to predict vehicle trajectories and establish a risk quantification model for vehicle-to-vehicle interaction behavior. Using SUMO software (win64-1.11.0), three typical driving behavior scenarios—car-following, lane-changing, and yielding—were modeled. A comparative analysis was conducted between the risk field quantification method and existing risk quantification indicators such as post-encroachment time (PET), deceleration rate to avoid crash (DRAC), modified time to collision (MTTC), and safety potential fields (SPFs). The evaluation results demonstrate that the risk field quantification method has the advantage of continuously quantifying risk, addressing the limitations of traditional risk indicators, which may yield discontinuous results when conflict points disappear. Furthermore, when the half-life parameter is reasonably set, the method exhibits more stable evaluation performance. This research provides a theoretical basis for the dynamic equilibrium control of driving risks in connected autonomous vehicle fleets within mixed-traffic environments, offering insights and references for collision avoidance design.

Alternative Role of B/b Knob-Hole Interactions in the Fibrin Assembly.

The self-assembly of fibrin is a vital process in blood clotting, primarily facilitated by the interactions between knobs "A" and "B" in the central E region of one molecule and the corresponding holes "a" and "b" in the peripheral D regions of two other fibrin molecules. However, the precise function of the interactions between knob "B" and hole "b" during fibrin polymerization remains a subject of ongoing debate. The present study focuses on investigating intermolecular interactions between knob "B" and hole "b". We investigated the D-E-D interactions within the fibrin protofibril to accomplish this objective. Our investigation involved studying the formation of supramolecular complexes involving desAB fibrin with fibrin(ogen) fragments, specifically the D-dimer and D fragment. The research utilized analytical size-exclusion chromatography, SDS-PAGE and densitometry of SDS-PAGE images, dynamic light scattering measurements, turbidity studies, electron microscopy, and computer modeling. Our findings indicate that the interference of the D fragment into classical D-E-D interaction occurs through knob "B" of the fibrin molecule. Molecular dynamics simulations elucidate the binding of only one D region, attributed to the shift of the D-dimer toward the fibrin desAB molecule. The formation of such a complex can be considered evidence supporting the potential mechanism of the branching of protofibrils. According to this theoretical mechanism, the inclusion of the D region from an external fibrin molecule into D-E-D interactions is facilitated through "B/b" contacts.

Solvatochromic Analysis of Triton X-100 in Binary Mixtures

Binary solvent mixtures of the non-ionic surfactant Triton X-100 with water, methanol, ethanol, and 1-propanol, respectively, were investigated by solvatochromic studies. The absorption spectral bands of methyl red dye, used as a solvatochromic probe, were recorded in ternary solutions prepared with different mole ratios between Triton X-100 and water/alcohols. The Kamlet–Abboud–Taft model was applied to estimate the contribution of each type of intermolecular interaction to the total shift of the electronic absorption band of the solute. The composition of the solute molecule’s first solvation shell was comparatively estimated by using three models: the statistical cell model of ternary solutions, the Suppan model, and the Bosch–Rosés model. The statistical cell model allows the estimation of the difference between the interaction energies in the solute–solvent pairs of molecules. The Bosch–Rosés model provided important information on the 1:1 complex formed between Triton X-100 and water/alcohol molecules, as well as on the symmetry/asymmetry related to the binary mixtures in the cybotactic region of the solute’s molecule.

Nuclear Magnetic Resonance Gas-Phase Studies of Spin-Spin Couplings in Molecules

This paper overviews gas phase experiments with respect to one fundamental part of nuclear magnetic resonance (NMR) spectra. Indirect spin-spin coupling is an important parameter of NMR spectra and is observed as the splitting of spectral signals. A molecule containing two different magnetic nuclei (e.g., hydrogen HD, HT, or DT) exhibits this interaction in an external magnetic field measured as the spin-spin coupling parameter, nJ(NN′). Modern quantum chemical methods allow the precise calculation of spin-spin coupling, but it is never easy because nJ(NN′) is modified by temperature and intermolecular interactions. Accurate calculations can be performed only for small isolated molecules. NMR spectroscopy can deliver measurements of spin-spin couplings for isolated molecules if nJ(NN′) parameters are observed in the gas phase as a function of density. The extrapolation of such measurements to the zero-density limit permits nJ0(NN′) determination free from intermolecular interactions. The latter technique can also be applied to liquid vapors in molecules like acetonitrile or water. Spin-spin couplings across one chemical bond (1J0(NN′)) are the largest and most important for theoretical modeling. The present review reports numerous 1J0(NN′) parameters recently measured by multinuclear NMR spectra of gaseous samples.

Four Polymorphs of the Bioactive Diuretic Drug 4-Chloro-5-chlorosulfonyl Salicylic Acid

4-chloro-5-chlorosulfonyl salicylic acid [C7H4Cl2O5S] is a derivative of salicylic acid and a diuretic agent. Its ability to form polymorphs through recrystallization from various solvents was demonstrated. As a result, four polymorphs were successfully obtained and analyzed using single-crystal X-ray diffraction and powder X-ray diffraction, which represents a novelty regarding the polymorphism of this compound of pharmaceutical interest. The solid-state properties were investigated by evaluating crystal lattice energies and intermolecular interactions.

Strengthened Effect of Surface-Active Ionic Liquids on Curcumin Solubility and Extraction Performance of Curcuminoids

As a kind of bioactive component in the rhizome of natural plant Curcuma longa L. (turmeric), curcumin is almost insoluble in water at neutral and acidic pH, which limits its further utilization and development. At the same time, traditional extraction and separation processes typically require the use of a large number of organic solvents. Ionic liquids (ILs) are organic molten salts with melting points below 100 °C. When an ionic liquid exists in a liquid state at or near room temperature, it is referred to as a room-temperature ionic liquid (RTIL). They have a temperature range, good physical and chemical stability, and good structural designability. They have a strong solubilization enhancement effect for many organic compounds. This study first explored the molecular forms of curcumin in ionic liquid aqueous solutions and the intermolecular interactions between curcumin and ionic liquids using spectral analysis and computational chemistry methods; furthermore, using an ionic liquid aqueous solution as an extraction agent, curcumin-like substances (curcuminoids) were extracted from turmeric powders under ultrasound assisted conditions, revealing the relationship between the structure of the ionic liquid and the extraction efficiency. After that, a kinetic study was conducted for the extraction of curcuminoids from turmeric powders, using second-order kinetics fitting to obtain the rate constant and initial extraction rate during the extraction process. Finally, the comparison with a ComplexGAPI tool and antioxidant experiment was performed on the extraction by using ionic liquids and traditional solvent. The full results can provide reference for the design of IL extractants and their application for natural products.

Chloride and Acetonitrile Ruthenium(IV) Complexes: Crystal Architecture, Chemical Characterization, Antibiofilm Activity, and Bioavailability in Biological Systems

Due to the emergence of drug resistance, many antimicrobial medications are becoming less effective, complicating the treatment of infections. Therefore, it is crucial to develop new active agents. This article aims to explore the ruthenium(IV) complexes with the following formulas: (Hdma)2(HL)2[RuIVCl6]·2Cl·2H2O (1), where Hdma is protonated dimethylamine and L is 2-hydroxymethylbenzimidazole, and [RuIVCl4(AN)2]·H2O (2), where AN is acetonitrile. This paper delves into the physicochemical characteristics and crystal structures of these complexes, employing various techniques such as spectroscopy (IR, UV–Vis), electrochemistry (CV, DPV), and X-ray crystallography. Hirshfeld surface analysis was also performed to visualize intermolecular interactions. Furthermore, the potential antibiofilm activity of the complexes against Pseudomonas aeruginosa PAO1 was investigated and the effect of the compounds on the production of pyoverdine, one of the virulence factors of the Pseudomonas strain, was assessed. The results show that particularly complex 1 reduces biofilm formation and pyoverdine production. Additionally, the bioavailability of these complexes in biological systems (by fluorescence quenching of human serum albumin (HSA) and molecular docking studies) is discussed, assessing how their chemical properties influence their interactions with biological molecules and their potential therapeutic applications.

Peptide-Based Complex Coacervates Stabilized by Cation-π Interactions for Cell Engineering.

Complex coacervation is a form of liquid-liquid phase separation, whereby two types of macromolecules, usually bearing opposite net charges, self-assemble into dense microdroplets driven by weak molecular interactions. Peptide-based coacervates have recently emerged as promising carriers to deliver large macromolecules (nucleic acids, proteins and complex thereof) inside cells. Thus, it is essential to understand their assembly/disassembly mechanisms at the molecular level in order to tune the thermodynamics of coacervates formation and the kinetics of cargo release upon entering the cell. In this study, we designed histidine-rich peptides consisting of modular sequences in which we systematically incorporate cationic, anionic, or aromatic residues at specific positions along the sequence in order to modulate intermolecular interactions and the resulting coacervation stability. We show that cation-π interactions between arginine and aromatic side chains are particularly efficient in stabilizing complex coacervates, and these interactions can be disrupted in the protein-rich intracellular environment, triggering the disassembly of complex coacervates followed by cargo release. With the additional grafting of a disulfide-based self-immolative side chain, these complex coacervates exhibited enhanced stability and could deliver proteins, mRNA, and CRISPR/Cas9 genome editing tools with tunable release kinetics into cells. This capability extends to challenging cell types, such as macrophages. Our study highlights the critical role of cation-π interactions in the design of peptide-based coacervates, expanding the biomedical and biotechnology potential of this emerging intracellular delivery platform.

Molecular miscibility of ASD blend components: an evaluation of (the added value of) solid state NMR spectroscopy and relaxometry.

In order to evaluate the stability of an amorphous solid dispersion (ASD) it is crucial to be able to accurately determine whether the ASD components are homogeneously mixed or not. Several solid-state analysis techniques are at the disposal of the formulation scientist, such as for example modulated differential scanning calorimetry (mDSC) and solid-state nuclear magnetic resonance spectroscopy (ssNMR). ssNMR is a robust, versatile, and accurate analysis technique with a large number of application possibilities. Especially ssNMR relaxometry, which allows the measurement of the proton relaxation times T1H and T1ρH, is very useful for evaluating the miscibility of ASDs. In this paper, the miscibility of a model ASD, composed of indomethacin (IND) and poly(vinylpyrrolidone-co-vinyl acetate) (PVPVA), was assessed using mDSC and various ssNMR techniques, in order to compare the different techniques and to evaluate the advantages and disadvantages of each. It was found that measuring the relaxation times via the chemical shift selective carbon signals using 13C-cross-polarization magic angle spinning (13C-CPMAS) is still the golden standard to evaluate miscibility, even giving information about the miscibility at the nm scale. Although non-chemical shift selective 1H-wideline measurements are significantly faster than 13C-CPMAS measurements to determine the relaxation times, the results are often hard to interpret, especially with regard to the T1ρH relaxation times. 2D 1H-13C dipolar heteronuclear correlation (dipolar HETCOR) NMR is an additional technique that can be used, and which provides information about the special proximity of 1H and 13C nuclei with respect to each other and therefore about the miscibility of the components at the nm scale. Additionally, it often allows to acquire information regarding the intermolecular interactions and the functional groups involved. Nevertheless, optimalization of the experiments, data processing and interpretation of the results require some expertise. Compared to mDSC, the ssNMR techniques are more sensitive and robust and can often provide information about the miscibility at nm scale. However, mDSC is a very fast analysis technique that requires less optimalization. Therefore, it remains recommended to use mDSC always for a first screening and as a complementary analysis technique.

Spectral narrowing strategiesin multiple resonance thermally activated delayed fluorescencematerials.

Multi-resonance thermally activated delayed fluorescence (MR-TADF) materials possess unique advantages of high-efficiency and narrowband emission, which have rapidly occupied an important position in the field of organic light-emitting diodes (OLEDs). In recent years, significant advancements have been made in the development of MR-TADF materials, particularly in achieving spectral narrowing for high-color-purity OLED applications. Based on diverse MR-TADF molecular skeletons, this review summarizes the primary molecular strategies to narrow spectrum by suppressing structural relaxation and intermolecular interactions. Key strategies include π-conjugation extension, increased molecular rigidity, and the introduction of bulky substituents and intramolecular hydrogen bonds. Additionally, effects of these strategies on photophysical properties are discussed. These molecular design strategies are expected to offer valuable insights for the future design of high-efficiency, narrowband OLED emitters.

From Hard Crystal to Soft Fiber: Thermochromic Color‐Tunable and “On‐Off”‐Switchable Afterglow of Single‐Component Ultralong RTP Organogel

AbstractPure organic stimuli‐responsive phosphorescent materials with multi‐color afterglows, good reversibility, and ease manipulation are highly appealing for dynamic anti‐counterfeiting applications, but remain challenging to achieve. In this work, a phosphorescent soft organogel is rationally designed by introducing functional carbonyl (benzoyl or acetyl) units into dibenzofuran skeleton to promote the intersystem crossing (ISC), and screening potential organogelators through predicting the self‐assembly process with the aid of all‐atom molecular dynamic simulation (AMDS). AMDS indicates that the designed gelator candidates (DBF‐Me and DBF‐Ph) can self‐assemble in the mixture of DMSO/H2O through balanced π‐π intermolecular interactions between neighboring molecules, thus promoting the gelation. Notably, the DBF‐Ph fiber gel exhibits a yellow afterglow at room temperature (298 K) with a lifetime of 235.1 ms, which can be switched off at 358 K but restored after cooling to room temperature. Furthermore, the yellow afterglow (298 K) can turn to green at 208 K and blue at 77 K, due to the slight change of conformation and molecular packing as revealed by analysis of temperature‐dependent single crystal structures. This single‐component DBF‐Ph fiber gel, capable of achieving color‐tunable and “on‐off”‐switchable afterglow through a single temperature response, offers significant potential in developing soft ultralong RTP materials for multi‐level anti‐counterfeiting features.

Impact of Polymer Physicochemical Features on the Amorphization and Crystallization of Citric Acid in Solid Dispersions

The amorphization and crystallization of citric acid in the presence of a variety of polymers were investigated. Polymers were chosen for their different physicochemical features, including hygroscopicity, glass transition temperature (Tg), and functional groups capable of forming intermolecular non-covalent interactions with citric acid. Citric acid solutions with varying amounts of pectin (PEC), guar gum (GG), κ-carrageenan (KG), gelatin (GEL), (hydroxypropyl)methylcellulose (HPMC), and carboxymethylcellulose sodium (CMC-Na) were lyophilized. Dispersions were stored for up to 6 months in controlled temperature and relative humidity environments and periodically monitored using powder X-ray diffraction, differential scanning calorimetry, and Fourier transform infrared spectroscopy. Moisture sorption isotherms and moisture contents were determined. Amorphous solid dispersions of citric acid were successfully formed in the presence of ≥20% w/w CMC-Na and PEC or ≥30% w/w of the other polymers except KG which required a minimum of 40% polymer. All samples remained amorphous even in their rubbery state at 0% RH (25 °C and 40 °C), but increasing the RH to 32% RH resulted in citric acid crystallization in the KG dispersions, and further increasing to 54% RH resulted in crystallization in all samples. Polymer effectiveness for inhibiting citric acid crystallization was CMC-Na > PEC ≥ GEL > HPMC > GG > KG. To create and maintain amorphous citric acid, polymer traits in order of effectiveness were as follows: greater propensity for intermolecular non-covalent interactions (both ionic and hydrogen bonding) with the citric acid, carbonyl groups, higher Tg, and then lower hygroscopicity.