Rearrangement Of Chemical Bonds Research Articles

Electropolymerized Bipolar Poly(2,3-diaminophenazine) Cathode for High-Performance Aqueous Al-Ion Batteries with An Extended Temperature Range of -20 to 45°C.

Achieving reversible insertion/extraction in most cathodes for aqueous aluminum ion batteries (AAIBs) is a significant challenge due to the high charge density of Al3+ and strong electrostatic interactions. Organic materials facilitate the hosting of multivalent carriers and rapid ions diffusion through the rearrangement of chemical bonds. Here, a bipolar conjugated poly(2,3-diaminophenazine) (PDAP) on carbon substrates prepared via a straightforward electropolymerization method is introduced as cathode for AAIBs. The integration of n-type and p-type active units endow PDAP with an increased number of sites for ions interaction. The long-range conjugated skeleton enhances electron delocalization and collaborates with carbon to ensure high conductivity. Moreover, the strong intermolecular interactions including π-π interaction and hydrogen bonding significantly enhance its stability. Consequently, the Al//PDAP battery exhibits a large capacity of 338 mAh g-1 with long lifespan and high-rate capability. It consistently demonstrates exceptional electrochemical performances even under extreme conditions with capacities of 155 and 348 mAh g-1 at -20 and 45°C, respectively. In/ex situ spectroscopy comprehensively elucidates its cation/anion (Al3+ /H3 O+ and ClO4 - ) storage with 3-electron transfer in dual electroactive centers (C═N and -NH-). This study presents a promising strategy for constructing high-performance organic cathode for AAIBs over a wide temperature range.

A Dual Active Site Organic–Inorganic Poly(O‐Phenylenediamine)/NH4V3O8 Composite Cathode Material for Aqueous Zinc‐Ion Batteries

AbstractAqueous zinc‐ion batteries, considered one of the important candidate technologies for green and environmentally friendly large‐scale energy storage, hinge upon the performance of cathode materials as the key factor driving their development. Vanadate oxide is a promising cathode material due to its high theoretical capacity; furthermore, in order to accelerate the reaction kinetics, ion or molecular intercalation is often utilized. However, non‐electrochemically active intercalants tend to cause capacity degradation. In this study, a one‐step hydrothermal method is employed to intercalate electrochemically active poly‐o‐phenylenediamine (PoPDA) into the interlayers of NH4V3O8 (NVO), with graphene oxide (GO) being used to further improve the conductivity of the composite material (NVO/PoPDA@GO). The insertion of PoPDA expands the interlayer spacing of the NVO, alters the charge distribution, and enhances the migration rate of Zn2+ among the hybrid materials. Additionally, PoPDA serves as a support within the interlayers, improving the material stability. Moreover, the reversible transformation and rearrangement of chemical bonds (C═N/C─N) in PoPDA allows for coordination with Zn2+, providing additional capacity. As a result, NVO/PoPDA@GO exhibits excellent electrochemical performance, releasing a specific capacity of 433 mAh g−1 at 0.5 A g−1, even with a capacity of 224 mAh g−1 at 5 A g−1. This work provides a promising direction for the preparation of organic–inorganic composite cathode materials with dual active components.

Effect of heat treatment on conformation and aggregation properties of wheat bran dietary fiber-gluten protein

To understand the heat mediated cross-linking mechanism of gluten in the presence of wheat bran dietary fiber (WBDF), the effect of heat treatment on conformation and aggregation properties of wheat bran dietary fiber-gluten protein was comparatively investigated in this study. The results showed G' and G" increased after adding WBDF, then decreased after heating. The SE-HPLC, chemical interaction and surface hydrophobicity analysis revealed the WBDF participated in the rearrangement of intermolecular interactions and induced depolymerization behavior behavior of gluten via disulfide and non-covalent bonds at low temperatures (25 °C and 60 °C), but heating (at 95 °C) promoted these interactions via disulfide bonds. Besides, changes in the secondary structure of gluten protein induced by WBDF during heating were correlated with the steric hindrance and hydroxyl groups on WBDF. These results suggested that WBDF impeded the cross-linking and aggregation of gluten through the rearrangement of chemical bonds and physical entanglements, then this effect was weakened at high temperatures, most likely by improving the disulfide bonds among gluten proteins. This study consummates the understanding of the cross-linking mechanisms of gluten with WBDF during heating, and provides the theoretical basis for improving the quality and acceptability of whole wheat-based products.

The Content and Principle of the Rare Ginsenosides Produced from Gynostemma pentaphyllum after Heat Treatment.

Ginsenoside Rg3, Rk1, and Rg5, rare ginsenosides from Panax ginseng, have many pharmacological effects, which have attracted extensive attention. They can be obtained through the heat treatment of Gynostemma pentaphyllum. In this study, scanning electron microscopy (SEM) and thermal gravity-differential thermal gravity (TG-DTG) were employed to investigate this process and the content change in ginsenosides was analyzed using liquid chromatography-mass spectrometry (LC-MS). SEM and TG-DTG were used to compare the changes in the ginsenosides before and after treatment. In SEM, the presence of hydrogen bond rearrangement was indicated by the observed deformation of vascular bundles and ducts. The before-and-after changes in the peak patterns and peaks values in TG-DTG indicated that the content of different kinds of compounds produced changes, which all revealed that the formation of new saponins before and after the heat treatment was due to the breakage or rearrangement of chemical bonds. Additionally, the deformation of vascular bundles and vessels indicated the presence of hydrogen bond rearrangement. The glycosidic bond at the 20 positions could be cleaved by ginsenoside Rb3 to form ginsenoside Rd, which, in turn, gave rise to ginsenoside Rg3(S) and Rg3(R). They were further dehydrated to form ginsenoside Rk1 and Rg5. This transformation process occurs in a weak acidic environment provided by G. pentaphyllum itself, without the involvement of endogenous enzymes. In addition, the LC-MS analysis results showed that the content of ginsenoside Rb3 decreased from 2.25 mg/g to 1.80 mg/g, while the contents of ginsenoside Rk1 and Rg5 increased from 0.08 and 0.01 mg/g to 3.36 and 3.35 mg/g, respectively. Ginsenoside Rg3(S) and Rg3(R) were almost not detected in G. pentaphyllum, and the contents of them increased to 0.035 and 0.23 mg/g after heat treatment. Therefore, the rare ginsenosides Rg3(S), Rg3(R), Rk1, and Rg5 can be obtained from G. pentaphyllum via heat treatment.

Vanadium Oxide Intercalated with Conductive Metal–Organic Frameworks with Dual Energy‐Storage Mechanism for High Capacity and High‐Rate Capability Zn Ion Storage

AbstractVanadium oxides (VOx) feature the potential for high‐capacity Zn2+ storage, which are often preintercalated with inert ions or lattice water for accelerating Zn2+ migration kinetics. The inertness of these preintercalated species for Zn2+ storage and their incapability for conducting electrons, however, compromise the capacity and rate capability of VOx. Herein, Ni‐BTA, a 1D conductive metal–organic framework (c‐MOF), is intercalated into the interlayer space of VOx by coordinating organic ligands with preinserted Ni2+. The intercalated Ni‐BTA improves the conductivity of VOx by π–d conjugation, facilitates Zn2+ migration by enlarging its interlayer spacing, and stabilizes the crystal structure of VOx as interlayer pillars, thus simultaneously enhancing the material's rate capability and cycling stability. Meanwhile, a dual reaction mechanism of Zn2+ storage, i.e., the redox of V5+/V3+ in VOx and the rearrangement of chemical bonds (CN/CN) in Ni‐BTA, collaboratively contributes to an enhanced capacity. Consequently, this Ni‐BTA‐intercalated VOx material exhibits a high Zn2+ storage capacity of 464.2 mAh g−1 at 0.2 A g−1 and an excellent rate capability of 272.5 mAh g−1 at 5 A g−1. This work provides a general strategy for integrating c‐MOFs with inorganic cathode materials to achieve high‐capacity and high‐rate performance.

Specific features of microhardness and thermodynamic stability of the Cd1–xMnxTe solid solutions

The features of fusion and growth of Cd1–xMnxTe (0.02 x  0.55) solid solution crystals as well as the dependence of their microhardness on the composition have been studied. Local maxima of the microhardness at x = 0.14 and 0.46 have been experimentally found. Thermodynamics of Cd1–xMnxTe formation in the delta-lattice parameter model has been considered, and the phase diagram of spinodal decomposition in these solid solutions has been found. The empirical pseudopotential method was used to analyze the distribution of the valence charge density during formation of the Cd1–xMnxTe solid solution and its effect on the rearrangement of chemical bonds. It has been shown that the stability of the solid solutions is defined not only by the difference in the lattice constants of the CdTe and MnTe binary compounds but also by the charge exchange between bonds with the different degree of ionicity and the change in the nature of chemical bonds.

Insight into a stepped fragmentation of coal-related model compounds using a tandem Orbitrap mass spectrometer

To provide basic knowledge for coal conversion, twenty one coal-related model compounds (MCs) were analyzed using a tandem Orbitrap mass spectrometer (MS). Higher-energy collisional dissociation (HCD), a method of Orbitrap MS, unraveled the detailed fragmentation pathways and de-alkylation behaviors of the ionized MCs under collision energies from 10 to 80 eV. Chemical bond breaking, hydrogen loss, rearrangement reaction, and elimination of neutral fragments were discussed to elucidate clear fragmentation pathways. For arenes without alkyl chains, a higher energy threshold of fragmentation was observed with the increasing of aromatic ring due to a higher conjugate effect of condensed aromatic structure. The existence of alkyl chains decreased the threshold of fragmentation because of the electron-donating effect of alkyl chains. Heteroatom-containing aromatic compounds, a series of important species in coal, showed a diversified fragmentation patterns due to a low bond dissociation energy and a weak conjugate effect compared with arenes. Fragmentation pathways and de-alkylation behaviors of coal-related MCs will contribute to building monitoring methods for coal and its derivatives conversions in chemical industry.

Polypyrrole as an ultrafast organic cathode for dual-ion batteries

Organic electrode materials based on the chemical bond cleavage/recombination working principle usually produce unimpressive reaction kinetics and stability. In this work, polypyrrole (PPy) is investigated as an ultrafast (87% retention at 20 ​A ​g−1) and stable (83% retention across 3000 cycles) cathode material in PPy|graphite dual-ion batteries. The fast intrinsic reaction kinetics, coupled with a capacitance-dominated mechanism, enable PPy to bypass the sluggish chemical bond rearrangement process. Electrochemically induced secondary doping improves the ordered aggregation of polymer chains and thus has a profound impact on anion diffusion and electrical conductivity. The excellent rate capability presented here changes our understanding of organic electrode materials and could prove useful for designing ultrafast rechargeable electrochemical devices.

Dynamic Spin-Spin Interaction Observed as Interconversion of Chemical Bonds in Stepwise Two-Photon Induced Photochromic Reaction.

Biradicaloids in π-conjugated organic molecules have been extensively studied in recent years because of the fundamental insights into the chemical bonds and unique optical, electrical, and magnetic properties. Several studies have reported that the spin-spin interactions of biradicaloids with flexible molecular frameworks dynamically evolve correlating with molecular structural changes. Although these dynamic behaviors will provide important insights into the relationship between molecular structures and spin properties, studies on such behaviors have been limited to two-spin systems. Here, we investigated the stepwise photochromic properties of biphotochromic molecules involving multiple spin interactions by double-pulse laser flash photolysis. The one-photon photochromic reaction generates the o-biradical form as the open-closed form, which thermally isomerizes to the o-quinoidal form and reaches the thermal equilibrium state between them. The additional absorption of a photon by the open-closed form leads to the photochromic reaction of the other photochromic unit, resulting in the generation of unpaired spins at the p-position of the central aromatic bridge of the biradical or quinoidal form. Under the situation, while the interaction between the unpaired spins and the o-biradical preferentially produces the p-quinoidal form in which the antiferromagnetic interaction at the p-position is dominant, that between the spins and the o-quinoidal form kinetically produces the bis(o-quinoidal) form followed by the thermal isomerization to the thermodynamically stable p-quinoidal form. These dynamic spin-spin interactions along with the rearrangement of chemical bonds will give a deeper understanding of the singlet biradicaloids and that to bridge organic multiradicals in molecular systems to cooperative spin behaviors in bulk materials.

Activation of film growth on indium phosphide by pulsed photon treatment

Photon activation of various physicochemical processes by the radiation of powerful pulsed xenon lamps (radiation range of 0.2-1.2 µm) is one of the promising areas of material science. The aim of this study was to determine the effect of preoxidative pulsed photon treatment on the process of thermal oxidation of indium phosphide with a nanosized layer of V2O5 on the surface, as well as its effect on the composition and morphology of the formed films. We determined the optimal mode of pre-oxidative pulsed photon treatment of magnetron-formed V2O5/InP heterostructures with a radiation density of 15 J/cm2. By laser and spectral ellipsometry methods, photon activation of V2O5/InP before thermal oxidation was found to increase the thickness of the formed films practically twofold. X-ray diffraction analysis confirms the intensification of the phosphate formation process. The morphological characteristics of the films were determined by atomic force microscopy.Pre-oxidative pulsed photon treatment with an optimal radiation density of 15 J/cm2 activates the thermal oxidation of V2O5/InP heterostructures. It is associated with the formation of new active centres and accelerated rearrangement of chemical bonds in the intermediate complexes of the V2O5 catalyst with semiconductor components

Recent advances in aggregation-induced emission of mechanochromic luminescent organic materials

Mechanochromic luminogenic materials (MCL) can reversibly modify their luminescence properties when exposed to external mechanical stimuli. This smart effect could emerge from physico-chemical characteristics varying in a wider scale, ranging from the transformation of molecular domains to the rearrangement of chemical bonds. MCL has become the fast-emerging group of materials owing to their great application potential as stress sensors, smart switches, optical memories, and optoelectronic and display devices. In recent years, a lot of work has been carried out on these materials leading to the synthesis of various MCL materials. This review discusses various organic MCL materials and their underlying luminogenic mechanisms. Furthermore, a detailed literature review of how different classes of luminescent organic materials respond to mechanical forces has been provided. In particular, the most common chromophores used in such systems including triphenylamine, cyanoethylene, pyrene, tetraphenylethene, and others are described here with an emphasis on their industrial applications. Presumably, this review will provide useful insights into the characteristics and applications of MCL materials to researchers working in this field in the academic community and industry.

Femtosecond Resolving Photodissociation Dynamics of the SO2 Molecule.

We experimentally investigate the ultrafast photodissociation dynamics of the SO2 molecule induced by intense ultrashort laser pulses in a pump-probe scheme. Different three-body fragmentation pathways are discriminated using the time-dependent kinetic energy release spectrum with femtosecond time resolution. A nontrivial three-body fragmentation pathway, denoted as the bonding pathway, is unraveled, in which an intermediate fast rotating O2 molecule is formed before complete fragmentation. The ultrafast chemical bond rearrangement after electron release is tracked in real time. The bonding pathway generally exists in the three-body fragmentation processes induced by strong laser fields of different wavelengths, which is observed in infrared, ultraviolet, and mixed two-color cases. Our findings are significant for understanding the photon-induced ultrafast processes of the SO2 molecule in atmospheric chemistry.

The Design of Quaternary Nitrogen Redox Center for High-Performance Organic Battery Materials

Summary Redox-active organic compounds attract broad research interest as a competitive candidate for battery electrode materials, owing to their structural diversity and elemental abundance. Currently, carbonyls, aza-derivatives, nitroxyl radicals, and thioethers dominate the research activities. However, the redox process of these compounds often involves chemical bond rearrangement or the formation of active intermediates, which seriously destabilize the structure. Here, we introduce an alternative strategy by using a quaternary nitrogen redox center for the design of stable organic battery materials. In such a strategy, empty orbital or lone pair electrons of the redox center participate in conjugation. During the redox reaction, the redox center is stabilized through conjugation without chemical bond rearrangement, thereby enhancing its stability. The oligomer of 5,10-diphenyl-dihydrophenazine following the proposed design strategy shows impressive cycling stability along with high redox potential, high thermal stability, and high specific energy and power density that are comparable with or superior to present organic cathode materials.

Dynamic covalent bonds: approaches from stable radical species

Dynamic covalent bonds by stable radical species are ideal platforms for simple, facile, and clean rearrangements of chemical bonds without the need for catalysts and the formation of byproducts.

Time-resolved high-harmonic spectroscopy of ultrafast ring-opening of 1,3-cyclohexadiene

We report, to the best of our knowledge, the first time-resolved high-harmonic spectroscopy (TR-HHS) study of a chemical bond rearrangement. We investigate the transient change of the high-harmonic signal from 1,3-cyclohexadiene (CHD), which undergoes ring-opening and isomerizes to 1,3,5-hexatriene (HT) upon photoexcitation. By associating the variation in the harmonic yield to the changes in the electronic state and vibrational frequencies of the molecule due to isomerization, we find that the CHD excited via two-photon absorption of 3.1 eV photons isomerizes to HT, i.e., ring-opening occurs, around 400 fs after the excitation. The present results demonstrate that TR-HHS, which can track both electronic and nuclear dynamics, is a powerful tool for studying ultrafast photochemical reactions.

Physics and chemistry in concert

Ultrafast Dynamics Shining a short, intense light pulse on a material can cause a transition in both its atomic and electronic structures. The dynamics of the electronic structure in such transitions can be monitored using, for example, time-resolved photoemission spectroscopy. Nicholson et al. observed a photoinduced metal-insulator transition in indium nanowires on a silicon surface. They monitored both the physics and the chemistry of the system after the initial photoexcitation and correlated the closing of the electronic bandgap with the rearrangement of chemical bonds. The results showcase the wealth of information that time-resolved tools can reveal about the dynamics of complex systems. Science , this issue p. [821][1] [1]: /lookup/doi/10.1126/science.aar4183

Beyond the molecular movie: Dynamics of bands and bonds during a photoinduced phase transition.

Ultrafast nonequilibrium dynamics offer a route to study the microscopic interactions that govern macroscopic behavior. In particular, photoinduced phase transitions (PIPTs) in solids provide a test case for how forces, and the resulting atomic motion along a reaction coordinate, originate from a nonequilibrium population of excited electronic states. Using femtosecond photoemission, we obtain access to the transient electronic structure during an ultrafast PIPT in a model system: indium nanowires on a silicon(111) surface. We uncover a detailed reaction pathway, allowing a direct comparison with the dynamics predicted by ab initio simulations. This further reveals the crucial role played by localized photoholes in shaping the potential energy landscape and enables a combined momentum- and real-space description of PIPTs, including the ultrafast formation of chemical bonds.

Time-resolved high-harmonic spectroscopy of ultrafast photoisomerization dynamics.

We report the first time-resolved high-harmonic spectroscopy (TR-HHS) study of a chemical bond rearrangement. We investigate the transient change of the high-harmonic signal from 1,3-cyclohexadiene (CHD), which undergoes ring-opening and isomerizes to 1,3,5-hexatriene (HT) upon photoexcitation. We associated the harmonic yield variation with the changes in the molecule's electronic state and vibrational frequencies, which are caused by isomerization. This showed us that the electronic excited state of CHD created through two-photon absorption of 3.1 eV photons relaxes almost completely within 100 fs to the electronic ground state of CHD with vibrational excitation. Subsequently, the molecule isomerizes to HT (i.e., ring-opening occurs, around 400 fs after the excitation). The present results demonstrate that TR-HHS, which can track both electronic and nuclear dynamics, is a powerful tool for studying ultrafast photochemical reactions.

Identifying the Multielectron Effect on Chemical Bond Rearrangement of CH3Cl Molecules in Strong Laser Fields

Strong field double ionization that triggers the chemical bond rearrangement of CH3Cl is investigated by impulsive control of the alignment of molecules. The alignment and laser intensity dependent H2+ and H3+ yields in linearly polarized femtosecond laser have been measured, and the obtained data show that the maximum signal of H2+ appears at the laser polarization parallel to the C-Cl axis of molecules and H3+ species are more likely to eject at the laser polarization parallel to the C-Cl axis at low laser intensity while the H3+ signal peaks at laser polarization perpendicular to the C-Cl axis at high laser intensity. The measurements indicate that electrons from HOMO - 1 and HOMO - 2 orbitals have been ionized for the generation of bond rearrangement at different laser intensity. Our results demonstrate the importance of multielectron effects and also provide an effective control method in the process of chemical bond rearrangement of the molecules in strong laser fields.

Evaluation of coal-related model compounds using tandem mass spectrometry.

Gas chromatography/mass spectrometry (GC/MS) is a routine and basic instrumental method for the analysis of complex coal conversion products in the chemical industry. To further enhance the practical potential of GC/MS in chemical industry, a tandem MS method for the selection of ion pairs applied in monitoring coal conversions was established using GC/quadrupole time-of-flight MS (GC/Q-TOF MS). The corresponding fragmentation pathways were explored and suitable ion pairs were screened. Fourteen coal-related model compounds (CRMCs) were analyzed using GC/Q-TOF MS with different collision-induced dissociation (CID) energies (5-20eV). The fragmentation pathways can offer a better understanding of chemical bond breaking, hydrogen transfer, rearrangement reactions and elimination of neutral fragments for CRMCs during the CID process. The precursor ions of aromatic hydrocarbons without alkyl chains were difficult to fragment with a CID energy of 20eV. But aromatic hydrocarbons with branched chains were prone to fragment via the loss of alkyl chains and further fragmented through ring-opening reactions. Compared with the Calk Car bond, the Car Car bond was difficult to fragment due to its high bond dissociation energy. The existence of heteroatoms facilitated fragmentation that was conducive to the screening of ion pairs. The CID technique of GC/Q-TOF MS will contribute to studies on the organic composition of coals and to building monitoring methods for coal conversions via fragmentation and ion pair selection.