Molecular Isomerization Research Articles

Boosting exciton dissociation in conjugated microporous polymers via molecular isomerization for photocatalytic degradation of antibiotics

Photocatalytic degradation of antibiotics from wastewater by polymeric photocatalysts is a powerful strategy to alleviate ecological damage and environmental pollution. Conjugated microporous polymers (CMPs) are promising in photocatalysis due to their tunable electronic structure and excellent light absorption. Nonetheless, CMPs still suffer from low exciton separation efficiency. Here, we propose a molecular isomerism strategy to promote exciton dissociation in CMPs by modulating the position of the carbonyl moiety. As a result, the introduction of carbonyl moiety with different substitution positions into the backbone of CMPs could minimize the exciton binding energy (Eb) and thus promote charge separation. PyCMPs-3 with phenanthrenequinone moiety as the acceptor featured a lower Eb of 37.19 meV, which are much smaller than that of carbonyl-free PyCMPs-1 (80.49 meV) and PyCMPs-2 (59.21 meV) with anthraquinone as the acceptor. Among them, PyCMPs-3 performed the best in photocatalytic degradation of ofloxacin (99 %) at a concentration of 144 ppm, which was significantly higher than that of its analogues PyCMPs-1 (26 %) and PyCMPs-2 (57 %) within 100 min under visible light exposure. In short, this work delivered a novel molecular isomerism strategy to minimize Eb by regulating the position of the carbonyl moiety for enhancing the photocatalytic degradation efficiency, promoting the development of CMPs for practical environmental remediation applications.

Decoding the Impact of Molecular Configuration on High‐Efficiency Blue Hot Exciton Emitters

AbstractRealizing highly efficient organic light‐emitting diodes (OLEDs) based on “hot exciton” emitters is crucial for the widespread use of purely organic electroluminescence. Herein, it is demonstrated that the radiative decay rate, modulated by molecular configuration, plays a vital role in determining the optoelectronic properties of hot exciton materials. The proof‐of‐concept isomers, TPA‐1IPCN and TPA‐3IPCN, and TPA‐1IANCN and TPA‐3IANCN are intentionally designed and successfully synthesized. By employing a novel donor–acceptor–acceptor (D–A'–A) molecular architecture, implementing a molecular isomerization strategy, incorporating diverse steric hindrance moieties, and strategically manipulating the positioning of functional groups, precise modulation of the molecular configuration can be achieved to enable accurate regulation of the radiative decay rate. Consequently, various optoelectronic properties, including photoluminescent wavelength, photoluminescence quantum yield, fluorescence lifetime, packing mode in aggregated state, and molecular horizontal dipole ratios in films, undergo significant modifications. As a result, non‐doped blue OLED based on TPA‐1IPCN exhibits outstanding maximum external quantum efficiency (EQE) of 10.3% with minimal efficiency roll‐off—one of the highest reported values for blue OLEDs based on hot exciton materials.

Taming of trinitromethyl-oxadiazole to access high density and high oxygen balance via a dual modulation strategy

Energetic compounds bearing the trinitromethyl group are garnering broad attraction as potential candidates for a new generation of high energy dense oxidizers. In this work, an effective dual modulation strategy involving both molecular isomerization and crystal morphology control was employed to design and optimize trinitromethyl-oxadiazole with improved comprehensive performance. Utilizing this dual strategy, 3,5-bis(trinitromethyl)-1,2,4-oxadiazole (3) was synthesized, resulting in the formation of two distinct crystal morphologies (needle and sheet) corresponding to two crystal forms (3-a and 3-b). Encouragingly, while maintaining ultra-high oxygen balance (21.73%), 3 achieves impressive densities (1.97–1.98 g/cm3). To our knowledge, the density of 1.98 g/cm3 for 3-a sets a new record among that of nitrogen-rich monocyclic compounds. Notably, practical crystal morphology prediction was creatively introduced to guide the experimental crystallization conditions of 3, increasing the impact sensitivity and friction sensitivity from 1 J to 80 N (3-a) to 10 J and 240 N (3-b), respectively. Additionally, the crystal structural analyses and theoretical calculations were conducted to elucidate the reasons of differences between 3-a and 3-b in density and stability. This work provides an efficient strategy to enhance performance of trinitromethyl derivatives, broadening the path and expanding the toolbox for energetic materials.

Theoretical study on the isomerization mechanism of visible light-driven azobenzene-based materials

This article investigates the geometric structure and isomerization mechanism of 4,4-acetamidazobenzene molecules with halogen atoms (F, Cl, Br) substituted at four ortho positions through density functional theory (DFT) calculations. The calculation method was b3lyp/g, and the base set was def2-tzvp. According to DFT calculations, the ortho substitution of the halogen atoms differently distorted the molecular plane of the trans isomers, resulting in obvious absorption peaks in the visible range, giving them visible-light driven properties. In addition, the transition state (TS) of the cis–trans isomerization reaction in the ground state was also found. To study the molecular isomerization mechanism, the potential energy surfaces (PESs) of the ground state (S0), first excited state (S1), and second excited state (S2) of halogen substituted azobenzene derivatives were scanned separately. Through the potential energy surface curve of the ground state, the mechanism of isomerization reaction in the ground state of the four molecules is realized through a rotation-assisted inversion pathway, which is consistent with the calculation of TS. When the molecules are in the excited states, the isomerization pathways are realized through rotation pathways.

ThermoBounce: Visualizing Chemical Kinetics via a Gravitational Potential Analogy

ThermoBounce is an interactive online visualization designed to help students understand how enthalpy, entropy, and temperature contribute to the reaction rate and equilibrium of a unimolecular chemical change between reactant and product states, for example, molecular isomerizations or phase transitions. At the start of the animation, reactant molecules are represented by spheres bouncing around in a reactant room, with an average kinetic energy proportional to the temperature. This room is connected to an adjacent product room by a window. When the user triggers the animation, spheres may convert to the product state by passing through the window into the product room, changing color as they do so. The difference between the floor heights of the reactant and product rooms represents the enthalpy change of the reaction, and the floor areas of the two rooms represent the entropies of the reactant and product states. The height of the bottom of the window above the floor of the reactant room represents the enthalpy of activation, and the width of the window represents the entropy of activation. Users can change the geometry of the rooms and window to adjust all these quantities and can modify the temperature before or during the reaction. They can then observe the resulting changes in the reaction rate and in the accumulation of product molecules, as shown on a reaction progress graph. The visualization and instructions for interacting with it are freely available on the Internet.

The role of memory-dependent friction and solvent viscosity in isomerization kinetics in viscogenic media

Molecular isomerization kinetics in liquid solvent depends on a complex interplay between the solvent friction acting on the molecule, internal dissipation effects (also known as internal friction), the viscosity of the solvent, and the dihedral free energy profile. Due to the absence of accurate techniques to directly evaluate isomerization friction, it has not been possible to explore these relationships in full. By combining extensive molecular dynamics simulations with friction memory-kernel extraction techniques we consider a variety of small, isomerising molecules under a range of different viscogenic conditions and directly evaluate the viscosity dependence of the friction acting on a rotating dihedral. We reveal that the influence of different viscogenic media on isomerization kinetics can be dramatically different, even when measured at the same viscosity. This is due to the dynamic solute-solvent coupling, mediated by time-dependent friction memory kernels. We also show that deviations from the linear dependence of isomerization rates on solvent viscosity, which are often simply attributed to internal friction effects, are due to the simultaneous violation of two fundamental relationships: the Stokes-Einstein relation and the overdamped Kramers prediction for the barrier-crossing rate, both of which require explicit knowledge of friction.

Structural Isomeric Effect on Spin Transport in Molecular Semiconductors.

Molecular semiconductor (MSC) is a promising candidate for spintronic applications benefiting from its long spin lifetime caused by light elemental-composition essence and thus weak spin-orbit coupling (SOC). According to current knowledge, the SOC effect, normally dominated by the elemental composition, is the main spin-relaxation causation in MSCs, and thus the molecular structure-induced SOC change is one of the most concerned issues. In theoretical study, molecular isomerism, a most prototype phenomenon, has long been considered to possess little difference on spin transport previously, since elemental compositions of isomers are totally the same. However, here in this study, quite different spin-transport performances are demonstrated in ITIC and its structural isomers BDTIC experimentally, for the first time, though the charge transport and molecular stacking of the two films are very similar. By further experiments of electron-paramagnetic resonance and density-functional-theory calculations, it is revealed that noncovalent-conformational locks (NCLs) formed in BDTIC can lead to enhancement of SOC and thus decrease the spin lifetime. Hence, this study suggests the influences from the structural-isomeric effect must be considered for developing highly efficient spin-transport MSCs, which also provides a reliable theoretical basis for solving the great challenge of quantificational measurement of NCLs in films in the future.

Modulating conjugated microporous polymers via molecular isomerism engineering for photoenhanced extraction of uranium from rare earth wastewater

Modulating conjugated microporous polymers via molecular isomerism engineering for photoenhanced extraction of uranium from rare earth wastewater

Enhancing solid-state photochromic performance of Stenhouse Adducts doped in bulk polymers by C3-Symmetric multipolar design

Here, we introduce a C3-symmetric molecular design strategy to develop a brand-new visible-light organic photoswitch, named tri-branched multipolar Stenhouse Adduct (TMSA). After doping TMSA into low glass transition polymers (i.e. thermoplastic urethane, TPU) via simple blending and solution casting, the resultant composite films exploit unique geometric and electronic effects of TMSA to afford markedly-improved photoswitching performance compared to those doped with dipolar donor-acceptor Stenhouse Adduct (DASA) counterparts with suppressed solid state photochromism. Importantly, they display good fatigue resistance over 50 photo-discoloration/thermal-recovery cycles with slow degradation, surpassing those literature-reported composites involving various DASAs (<30 cycles). As revealed by combined experiment and computation studies, the multi-dimensional electronic coupling in multipolar TMSA facilitates the thermal cyclization and non-planar branched structures of TMSA afford large free space in polymers for efficient molecular isomerization, while the promoting effect on TMSA isomerization induced by ester-rich polymer micro-environments is more pronounced relative to DASA counterpart.

Metastability and polymorphism in dihydroxybenzenes – implications for thermal energy storage

State-of-the-art experimental and computational techniques have been used to explore the effects of molecular isomerism on the phase behaviour of the three dihydroxybenzenes catechol, resorcinol, and hydroquinone.

Consumer Grade Polyethylene Recycling via Hydrogenolysis on Ultrafine Supported Ruthenium Nanoparticles.

Catalytic hydrogenolysis has the potential to convert high-density polyethylene (HDPE), which comprises about 30 % of plastic waste, into valuable alkanes. Most investigations have focused on increasing activity for lab grade HDPEs displaying low molecular weight, with limited mechanistic understanding of the product distribution. No efficient catalyst is available for consumer grades due to their lower reactivity. This study targets HDPE used in bottle caps, a waste form generated globally at a rate of approximately one million units per hour. Ultrafine ruthenium particles (1 nm) supported on titania (anatase) achieved up to 80 % conversion into light alkanes (C1 -C45 ) under mild conditions (498 K, 20 bar H2 , 4 h) and were reused for three cycles. Small ruthenium nanoparticles were critical to achieving relevant conversions, as activity sharply decreased with particle size. Selectivity commonalities and peculiarities across HDPE grades were disclosed by a reaction modelling approach applied to products. Isomerization cedes to backbone scission as the reaction progresses. Within this trend, low molecular weight favor isomerization whilst high molecular weight favor cleavage. Commercial caps obeyed this trend with decreased activity, anticipating the influence of additives in realistic processing. This study demonstrates effective hydrogenolysis of consumer grade polyethylene and provides selectivity patterns for product control.

Consumer Grade Polyethylene Recycling via Hydrogenolysis on Ultrafine Supported Ruthenium Nanoparticles

AbstractCatalytic hydrogenolysis has the potential to convert high‐density polyethylene (HDPE), which comprises about 30 % of plastic waste, into valuable alkanes. Most investigations have focused on increasing activity for lab grade HDPEs displaying low molecular weight, with limited mechanistic understanding of the product distribution. No efficient catalyst is available for consumer grades due to their lower reactivity. This study targets HDPE used in bottle caps, a waste form generated globally at a rate of approximately one million units per hour. Ultrafine ruthenium particles (1 nm) supported on titania (anatase) achieved up to 80 % conversion into light alkanes (C1−C45) under mild conditions (498 K, 20 bar H2, 4 h) and were reused for three cycles. Small ruthenium nanoparticles were critical to achieving relevant conversions, as activity sharply decreased with particle size. Selectivity commonalities and peculiarities across HDPE grades were disclosed by a reaction modelling approach applied to products. Isomerization cedes to backbone scission as the reaction progresses. Within this trend, low molecular weight favor isomerization whilst high molecular weight favor cleavage. Commercial caps obeyed this trend with decreased activity, anticipating the influence of additives in realistic processing. This study demonstrates effective hydrogenolysis of consumer grade polyethylene and provides selectivity patterns for product control.

Shape-Programmable Liquid-Crystalline Polyurethane-Based Multimode Actuators Triggered by Light-Driven Molecular Motors.

In recent years, light-driven soft actuators have been rapidly developed as enablers in the fabrication of artificial robots and biomimetic devices. However, it remains challenging to amplify molecular isomerization to multiple modes of macroscopic actuation with large amplitude and complex motions. Here, a strategy is reported to build a light-responsive liquid-crystalline polyurethane elastomer by phototriggered overcrowded alkene-based molecular motors. A trifunctional molecular motor modified with an ethylene glycol spacer on the rotor and stator functions as a crosslinker and unidirectional stirrer that amplifies molecular motion into macroscopic movement. The shape-programmable polymeric film presents superior mechanical properties and characteristic shape-memory effect. Furthermore, diverse modes of motions including bending, unwinding, and contracting with tunable actuation speed over a wide range are achieved. Such research is hoped to pave a new way for the design of advanced light-responsive soft actuators and robots.

Optimizing molecular potential models by imposing kinetic constraints with path reweighting.

Empirical force fields employed in molecular dynamics simulations of complex systems are often optimized to reproduce experimentally determined structural and thermodynamic properties. In contrast, experimental knowledge about the interconversion rates between metastable states in such systems is hardly ever incorporated in a force field due to a lack of an efficient approach. Here, we introduce such a framework based on the relationship between dynamical observables, such as rate constants, and the underlying molecular model parameters using the statistical mechanics of trajectories. Given a prior ensemble of molecular dynamics trajectories produced with imperfect force field parameters, the approach allows for the optimal adaption of these parameters such that the imposed constraint of equally predicted and experimental rate constant is obeyed. To do so, the method combines the continuum path ensemble maximum caliber approach with path reweighting methods for stochastic dynamics. When multiple solutions are found, the method selects automatically the combination that corresponds to the smallest perturbation of the entire path ensemble, as required by the maximum entropy principle. To show the validity of the approach, we illustrate the method on simple test systems undergoing rare event dynamics. Next to simple 2D potentials, we explore particle models representing molecular isomerization reactions and protein-ligand unbinding. Besides optimal interaction parameters, the methodology gives physical insights into what parts of the model are most sensitive to the kinetics. We discuss the generality and broad implications of the methodology.

Dye-free and reprintable multi-color DLP 3D printing using ZnCl2-based polymerizable deep eutectic solvents and type I photoinitiators

The current multi-color digital light processing (DLP) relies on different dyes and complex resin exchange/cleaning equipment to fabricate multi-color objects. Here, we developed a novel and simple approach to print multi-color objects using a conventional DLP printer with acrylic acid (AA)/ZnCl2/H2O (AZH)-based polymerizable deep eutectic solvents (PDESs) and type I photoinitiators, eliminating the need for dyes. The coloration of the printed objects is achieved by the molecular isomerization of type I photoinitiators remaining in the cured material. Furthermore, the color tuning range of the printed objects with this approach is close to the full-color gamut. Another advantage of this approach is that the printed objects can be recycled and reused to prepare the precursor solution for new multi-color DLP printing, making it a more sustainable and environmentally-friendly method. Finally, the potential application of multi-color objects in information encryption and decryption has been demonstrated, which opens new possibilities for the use of multi-color DLP printing in security and other areas. This novel multi-color DLP printing strategy utilizing residual photoinitiators represents a significant advancement in 3D printing technology, offering a simpler, more flexible, and more sustainable approach to achieving multi-color printing.

Molecular Conformational Isomerization: An Efficient Way to Design Novel Emitters with Dual-Thermally Activated Delayed Fluorescence Characteristics and Their Optoelectronic and Bioimaging Applications

Molecular Conformational Isomerization: An Efficient Way to Design Novel Emitters with Dual-Thermally Activated Delayed Fluorescence Characteristics and Their Optoelectronic and Bioimaging Applications

Selective control of donor-acceptor Stenhouse adduct populations with non-selective stimuli

Selective control of donor-acceptor Stenhouse adduct populations with non-selective stimuli

18.9% Efficiency Ternary Organic Solar Cells Enabled by Isomerization Engineering of Chlorine‐Substitution on Small Molecule Donors

AbstractTernary organic solar cells (OSCs) represent an efficient and facile strategy to further boost the device performance. However, the selection criteria and rational design of the third guest small molecule (SM) material still remain less understood. In this study, two new SM donor isomers, with α‐chlorinated thiophene (αBTCl) and β‐chlorinated thiophene (βBTCl) as side chains, are systematically designed, synthesized and incorporated as a third component in PM6:L8‐BO binary blends. It is noticed that introducing the SM donors guest has extended the absorption of photo‐active layer, induced desired component distribution vertically with enhanced crystallinity and reduced recombination process, leading to increased short‐circuit current (JSC) and improved fill factor. Moreover, due to the synergetic suppressed nonradiative loss and preferable morphology, the ternary OSCs feature improves open‐circuit voltage (VOC). Consequently, an impressive champion power conversion efficiency of 18.96% and 18.55% is achieved by αBTCl‐based and βBTCl‐based ternary OSCs, respectively. Furthermore, a record efficiency of 17.46% is obtained with a 330 nm thickness of αBTCl‐based ternary OSCs. This study demonstrates that molecular isomerization can be a promising design approach for SM donors to construct high‐performance ternary OSCs with simultaneous enhancement of all photovoltaic parameters.

ESIPT‐Inspired Dual‐Mode Photoswitches with Fast Molecular Isomerization in the Solid State

AbstractPhotoswitchable materials have attracted considerable attention in various fields. Developing excellent solid‐state dual‐mode photoswitches is an important but challenging task. Herein, we propose a new strategy to construct an excited‐state intramolecular proton transfer (ESIPT) inspired photoswitch (DiAH‐pht) that possesses aggregation‐induced emission (AIE) features and displays a fast molecular isomerization process characterized by dual‐mode behavior in the solid state. Mechanistic studies indicate that introduction of a bulky group can create a folded molecular conformation that provides adequate volume to facilitate photoisomerization and the enhanced ESIPT effect can boost the isomerization process. The feasibility of our strategy was further demonstrated by the activated photoisomerization performance of the Schiff base derivatives. Furthermore,DiAH‐phtshows good performance in the fields of dual‐mode information encryption and high‐density data storage.

ESIPT-Inspired Dual-Mode Photoswitches with Fast Molecular Isomerization in the Solid State.

Photoswitchable materials have attracted considerable attention in various fields. Developing excellent solid-state dual-mode photoswitches is an important but challenging task. Herein, we propose a new strategy to construct an excited-state intramolecular proton transfer (ESIPT) inspired photoswitch (DiAH-pht) that possesses aggregation-induced emission (AIE) features and displays a fast molecular isomerization process characterized by dual-mode behavior in the solid state. Mechanistic studies indicate that introduction of a bulky group can create a folded molecular conformation that provides adequate volume to facilitate photoisomerization and the enhanced ESIPT effect can boost the isomerization process. The feasibility of our strategy was further demonstrated by the activated photoisomerization performance of the Schiff base derivatives. Furthermore, DiAH-pht shows good performance in the fields of dual-mode information encryption and high-density data storage.