Ethylene Bridge Research Articles

Rotatable Methylene Ether Bridge Units Enabling High Chain Flexibility and Rapid Ionic Transport in a New Universal Aqueous Conductive Binder

AbstractBinders play an essential role in maintaining the mechanical integrity and stability of electrodes. Herein, a novel aqueous and conductive binder (OXP/CNT‐1.5) consisting of carbon nanotubes (CNTs) interwoven with a flexible nano‐film of oxidized pullulan (OXP) is designed. The rotatable methylene ether bridge units within OXP chain endow the binder with high chain flexibility, facilitate rapid ion transport, and buffer severe volumetric expansion during charge‐discharge cycling. Furthermore, its tight intertwining with CNTs forms continuously conductive and flexible skeletons, which can firmly grasp active nanoparticles through a “face‐to‐point” bonding type, guaranteeing the electrodes high conductivity and outstanding mechanical integrity. More importantly, these conductive binders are applicable to the Si/C anode as well as the LiFePO4 cathode. The as‐fabricated Si/C anode delivers a 88.2% capacity retention after 100 cycles and 80.2% capacity retention at 0.5 A g−1 (vs 0.05 A g−1), far surpassing the electrode fabricated by conventional polyvinylidene fluoride binder and carbon black mixtures. The LiFePO4/Si/C full cells based on OXP/CNT‐1.5 demonstrate excellent electrochemical behavior and stability (97.4% capacity retention after 100 cycles). This work highlights the key role of rotatable methylene ether bridge units to enhance the flexibility, ion conductivity, and stability, which is inspiring in the context of designing novel binders for high‐performance batteries.

UV-Excited Luminescence in Porous Organosilica Films with Various Organic Components.

UV-induced photoluminescence of organosilica films with ethylene and benzene bridging groups in their matrix and terminal methyl groups on the pore wall surface was studied to reveal optically active defects and understand their origin and nature. The careful selection of the film's precursors and conditions of deposition and curing and analysis of chemical and structural properties led to the conclusion that luminescence sources are not associated with the presence of oxygen-deficient centers, as in the case of pure SiO2. It is shown that the sources of luminescence are the carbon-containing components that are part of the low-k-matrix, as well as the carbon residues formed upon removal of the template and UV-induced destruction of organosilica samples. A good correlation between the energy of the photoluminescence peaks and the chemical composition is observed. This correlation is confirmed by the results obtained by the Density Functional theory. The photoluminescence intensity increases with porosity and internal surface area. The spectra become more complicated after annealing at 400 °C, although Fourier transform infrared spectroscopy does not show these changes. The appearance of additional bands is associated with the compaction of the low-k matrix and the segregation of template residues on the surface of the pore wall.

Reactivity of trans-Resveratrol toward Electrogenerated Superoxide in N,N-Dimethylformamide.

The reactivity of 5-[(E)-2-(4-hydroxyphenyl)ethen-1-yl]benzene-1,3-diol (trans-resveratrol) and related compounds toward electrogenerated superoxide radical anion (O2•-) were investigated using electrochemistry, in situ electrolytic electron spin resonance, and in situ electrolytic ultraviolet-visible spectral measurements, in N,N-dimethylformamide (DMF) with the aid of density functional theory (DFT) calculations. The quasi-reversible cyclic voltammogram of dioxygen/O2•- was modified by the presence of trans-resveratrol, suggesting that the electrogenerated O2•- was scavenged by trans-resveratrol through proton-coupled electron transfer (PCET) via three phenolic hydroxy groups (OH) on the stilbene moiety. The reactivity of trans-resveratrol toward O2•- characterized by the OHs was experimentally confirmed in comparative analyses using some related compounds, pinosylvin, pterostilbene, p-coumaric acid, and so on, in DMF. The electrochemical and DFT results suggested that a concerted PCET mechanism via 4'OH of trans-resveratrol proceeds, where the coplanarity of the two phenolic rings in the stilbene moiety linked by an ethylene bridge is essential for a successful O2•- scavenging.

NIR Absorbing Aromatic E-Ethylene Bridged Hexaphyrins (2.1.1.2.1.1): Synthesis, Characterization, and Protonation Studies.

Judicious syntheses, spectroscopic analyses, and solid state structural evidence of two structural variants (with planar geometry) of strongly aromatic hybrid [30] E-ethylene bridged hexaphyrins (2.1.1.2.1.1) exhibiting strong NIR absorption are reported. The induced correspondence of fused phenanthrene on the pyrrole moieties has led to a further red-shift of up to ∼45 nm in the neutral and protonated form of the macrocycles. The electronic nature and aromaticity of both hexaphyrins are fully supported by DFT calculations.

Synthesis and Properties of Norphthalocyanines Functionalized with a Tetrathiacrown Ether-Tetrathiafulvalene Substituent.

To construct novel ion receptors and D-A self-assembly systems for materials with better functions, the annulation of a tetrathiafulvalene donor with a magnesium norphthalocyanine core via a flexible tetrathiacrown ether bridge afforded a new triad 1. The structure of this product was characterized by 1H NMR and infrared spectroscopy, time-of-flight mass spectrometry, and elemental analysis. The optical and electrochemical properties were investigated using UV-vis spectroscopy and cyclic voltammetry. The complex of triad 1 and 2,3,5,6- tetrafluoro-7,7,8,8-tetracyanoquinodimethane produced electron transfer with a radical cationic character, as confirmed by UV-Vis and electron paramagnetic resonance analysis. Furthermore, the target compound presented evident intramolecular charge-transfer interactions in ground states, which were explained using density functional theory. Furthermore, norphthalocyanine 1 was able to coordinate Ag+ through the peripheral ligating oxathiaether crown.

Ambipolar Behavior of a Cu(II)–Porphyrin Derivative in Ternary Organic Solar Cells

Ternary architecture is a promising strategy to achieve high efficiency in organic solar cells. The alignment of third‐component frontier orbitals with those of donor and acceptor (D and A) is of essential importance. Herein, a new molecule VC11, consisting of a Cu(II)–porphyrin core linked to dicyanovinylene terminal acceptor units through (E)‐1,2‐di(thiophen‐2‐yl) ethene bridges, is described. The highest occupied molecular orbital and lowest unoccupied molecular orbital values of VC11 are −5.52 and −3.74 eV, respectively, lying between the corresponding values of PBDB‐T donor and Y6 acceptor, compounds used in the construction of the studied devices. The measured electron and hole mobilities reveal similar values, in the order of 10−4 cm2 Vs−1, indicating the ambipolarity of VC11, that can be used as donor or acceptor. The organic solar cells (OSCs) based on PBDB‐T:VC11, VC11:Y6, and PBDB‐T:Y6 show power conversion efficiencies (PCEs) of 10.84%, 7.89%, and 11.98%, respectively. VC11 is utilized along with PBDB‐T and Y6 to form a ternary active layer for assembling bulk heterojunction OSCs affording a remarkable PCE of 15.25%, significantly higher than those obtained for the corresponding binary devices. This enhancement of PCE originates from the additional charge separation offered by a cascaded energy‐level alignment and a fast charge transfer, due the ambipolarity of VC11.

Diamine Groups on the Surface of Silica Particles as Complex-Forming Linkers for Metal Cations

Novel spherically shaped organosilica materials with (propyl)ethylenediamine groups were obtained via a modified one-pot Stöber co-condensation method. The porosity of these materials was tuned with the controlled addition of three silica monomers acting as structuring agents (tetraethoxysilane and bridged silanes with ethylene and phenylene bridges). The morphologies and structures of the synthesized materials were studied by SEM, DRIFT spectroscopy, CHNS elemental analysis, low-temperature nitrogen adsorption-desorption, and electrokinetic potential measurements. Their sizes were in the range of 50 to 100 nm, depending on the amount of structuring silane used in the reaction. The degree of the particles' agglomeration determined the mesoporosity of the samples. The content of the (propyl)ethylenediamine groups was directly related with the amount of functional silane used in the reaction. The zeta potential measurements indicated the presence of silanol groups in bissilane-based samples, which added new active centers on the surface and reduced the activity of the amino groups. The static sorption capacities (SSCs) of the obtained samples towards Cu(II), Ni(II), and Eu(III) ions depended on the porosity of the samples and the spatial arrangement of the ethylenediamine groups; therefore, the SSC values were not always higher for the samples with the largest number of groups. The highest SSC values achieved were 1.8 mmolCu(II)/g (for ethylene-bridged samples), 0.83 mmolNi(II)/g (for phenylene-bridged samples), and 0.55 mmolEu(III)/g (for tetraethoxysilane-based samples).

Skeletal photoinduced rearrangement of diarylethenes: ethene bridge effects.

A skeletal photorearrangement involving UV-induced 6π-electrocyclization of diarylethenes with various ethene bridges has been studied. It has been found that deprotonation is the predominant step among the three possible alternative reaction pathways (radical abstraction, deprotonation, or sigmatropic shift) following 6π-electrocyclization, and incorporation of an electronegative carbonyl group into the geminal position to the phenyl residue results in a reduction in the reaction time and an increase in the yield of the desired product. The significant increase in the reaction time in less polar solvents (toluene, TCM) also indicates a large contribution of the deprotonation step to the skeletal photorearrangement of diarylethenes. Performing the reaction in toluene in the presence of tertiary amines leads to a reduction in the reaction time and an increase in the yield of the desired product. The best results were achieved when the reaction was carried out in toluene in the presence of DIPEA. The experimental results are in good agreement with the DFT calculations.

Caryophyllene sesquiterpenoids with various ring systems from the fungus Pestalotiopsis chamaeropis

Six undescribed caryophyllene sesquiterpenoids named pestalotiopsins O–T, along with eight known analogues, were obtained from the fungus Pestalotiopsis chamaeropis. Their structures and absolute configurations were assigned by NMR spectroscopic analyses, HRESIMS, single-crystal X-ray diffraction, electronic circular dichroism (ECD) calculations, Mo2(OAc)4-induced ECD, and chemical derivatization. Pestalotiopsin P represents the first example of a caryophyllene sesquiterpenoid possessing an oxatricyclo [7.2.2.03.6]tridecane decorated with a rare bridgehead double bond, while pestalotiopsin Q has an oxatricyclic [6.3.1.01,4]dodecane skeleton with an unusual ether bridge between C-1 and C-5. These undescribed caryophyllene sesquiterpenoids were screened for their cytotoxic and anti-inflammatory activities.

Chiral selection of Tröger's base-based macrocycles with different ethylene glycol chains length in crystallization

In the present work, two Trӧger's base-based macrocycles (TBBMs) with different bridging ethylene glycol chains (T1, n = 1; T3, n = 3) were successfully synthesized and studied via the crystal analysis. These two TBBMs possess rare rectangular-like cavities and show chiral selection during the crystallization. T1 with short glycol chain (n = 1) crystallized as racemates, while T3 with long glycol chain (n = 3) was found as meso isomer. In contrast to T1 and T3, for T2 (n = 2) both rac-T2 and meso isomer R2NS2N-T2 has been observed in our previous report. Thus, the synthesis of new TBBMs T1 and T3 with different bridging ethylene glycol chains not only makes the study of TBBMs more systematically, but also helps to understand the relationship between the size of the rectangular cavity and the chiral selection of Tröger's base-based macrocycles during their crystallization.

Discovery of BODIPY J-aggregates with absorption maxima beyond 1200 nm for biophotonics.

Organic dyes with absorption maxima in the second near-infrared window (NIR-II; 1000 to 1700 nm) are of great interest in biophotonics. However, because of the lack of appropriate molecular scaffolds, current research in this field is limited to cyanine dyes, and developing NIR-II-absorbing organic dyes for biophotonics remains an immense challenge. Here, we rationally designed an ethenylene-bridged BODIPY scaffold featuring excellent J-aggregation capabilities and revealed that the bridging ethylene unit is crucial for intermolecular J-coupling regulation. By integrating the electron-donating groups into the scaffold, we obtained a BODIPY dye, BisBDP2, with a J-aggregate absorption maximum of around 1300 nm. BisBDP2 J-aggregates show excellent photothermal performance, including intense photoacoustic response, and a high photothermal conversion efficiency value of 63%. In vivo results demonstrate the potential of J-aggregates for photoacoustic imaging and photothermal ablation of deep-seated tumors. This study will speed up the exploration of NIR-II-absorbing J-aggregates for future biophotonic applications.

Cholesterol Stationary Phase in the Separation and Identification of siRNA Impurities by Two-Dimensional Liquid Chromatography-Mass Spectrometry

The aim of this research was to develop a simple and efficient ion-pair reagent-free chromatographic method for the separation and qualitative determination of oligonucleotide impurities, exemplified by synthesis of raw products of the two single strands of patisiran siRNA. The stationary phases with mixed hydrophobic/hydrophilic properties (cholesterol and alkylamide) were firstly used for this purpose with reversed-phased high-performance liquid chromatography. Several different chromatographic parameters were tested for their impact on impurities separation: type, concentration, pH of salt, as well as organic solvent type in the mobile phase. The pH was the most influential factor on the separation and signal intensities in mass spectrometry detection. Finally, the optimized method included the application of cholesterol stationary phase, with mobile phase containing 20 mM ammonium formate (pH 6.5) and methanol. It allowed good separation and the identification of most impurities within 25 min. Since not all closely related impurities could be fully resolved from the main peak in this oligonucleotide impurity profiling, two-dimensional liquid chromatography was used for peak purity determination of the target oligonucleotides. The Ethylene Bridged Hybrid (BEH) Amide column in hydrophilic interaction liquid chromatography was applied in the second dimension, allowing additional separation of three closely related impurities.

Balancing Energy and Stability of Nitroamino-1,2,4-Oxadiazoles through a Planar Bridge.

By integrating two approaches─an ethene bridge to enhance safety and planarity to support good density─we have achieved new high-energy-density materials 4-8. Compounds 4-8 show good detonation performance (Dv = 8037-9305 m s-1 and DP = 24.7-33.4 GPa) and large enthalpies of formation (260.1-1444.9 kJ mol-1). The detonation velocity of compound 8 (9305 ms-1) approaches that of HMX (9320 ms-1), which suggests it is a competitive high-energy-density material.

Intramolecular Assembly of Nitrobiazoles and an Ether Bridge: Toward Energetic Materials with Enhanced Energy and Safety.

Recently, the construction of novel fused-ring frameworks has become one of the most significant innovative approaches to access high-energy and thermostable energetic molecules. In this work, an ether bridge was utilized as a building block to construct energetic fused-ring skeletons for the first time. Two new [5,7,5]-tricyclic N-heterocycle-based backbones, ditriazole-1,3,6-oxadiazepine and pyrazole-triazole-1,3,6-oxadiazepine, were synthesized via a straightforward one-step synthetic route and the energetic performances of their derivatives were further evaluated. Containing an additional oxygen atom, high-density pyrazole-triazole backbone, and high crystal packing coefficient, the asymmetric molecule 2,10,11-trinitro-5H,7H-pyrazolo[1,5-c][1,2,4]triazolo[5,1-e][1,3,6]oxadiazepine (NOB-3) features a high crystal density of 1.825 g cm-3, much superior to those of the symmetrical analogues 2,10-dinitro-5H,7H-bis([1,2,4]triazolo)[1,5-c:5',1'-e][1,3,6]oxadiazepine (NOB-4, d = 1.758 g cm-3) and D (d = 1.634 g cm-3). Meanwhile, the compounds NOB-3 and NOB-4 exhibit better thermal stability than the parent molecule DNBT (Td = 251 °C), and their decomposition temperatures reach up to 303 and 294 °C, respectively. The remarkable overall performance of NOB-3 and NOB-4 strongly suggests them as appropriate candidates for heat-resistant explosives. Our study may give new insights into the close correlation of the structural properties of energetic fused-ring frameworks, and the universality of the asymmetric heterocycles combination strategy for designing advanced high-energy density materials (HEDMs) was emphasized again.

Moldavica acid A, a new salicylic acid derivative from Dracocephalum moldavica

In this paper, we present the discovery of a novel salicylic acid derivative, moldavica acid A (1), and a new natural dibenzo[b,f]oxepin, moldavica acid B (2), together with four known phenylpropionic acids (3-6) and protocatechuic acid (7) that were isolated from Dracocephalum moldavica L. Their structures were elucidated by comprehensive spectroscopic methods, including infrared and nuclear magnetic resonance. Compound 1 is the first example of salicylic acid linking a carboxylated α-pyrone via an ethyl bridge. Beyond expanding the knowledge of the chemical diversity of D. moldavica, both compounds 1 and 2 were shown to upregulate the expression of Kruppel-like factor 2, which could serve as a prospective therapeutic target for the treatment of atherosclerosis.

Toward Advanced High-Performance Insensitive FOX-7-like Energetic Materials via Positional Isomerization.

For an energetic molecule with a definite elemental composition, the substituent type and position are the most important factors to influence its detonation performance and mechanical sensitivities. In this work, two pairs of FOX-7-like energetic isomers based on (2 and HTz-FOX; 5 and 6) were synthesized and characterized. Through positional isomerization, advanced high-performance insensitive explosives were obtained. Compounds 2 and 5 with an amino group adjacent to the electron-withdrawing side of the ethene bridge show both higher thermal stability and lower mechanical sensitivities (2: Td = 258 °C, impact sensitivity (IS) = 25 J, and friction sensitivity (FS) = 300 N; 5: Td = 264 °C, IS = 30 J, and FS = 320 N). In addition, 2 shows ultrahigh detonation performance (Dv = 9224 m s-1 and P = 31.1 GPa). These promising physicochemical properties are comparable to those of HMX (Dv = 9193 m s-1, P = 37.8 GPa, Td = 275 °C, IS = 7.4 J, and FS = 120 N), which suggests that 2 may be a promising energetic material in future applications.

Sterically Hindered Diarylethenes with a Benzobis(thiadiazole) Bridge: Enantiospecific Transformation and Reversible Photosuperstructures.

ConspectusPhotochromic diarylethenes featuring reversible regulation by external light irradiation have attracted increasing attention in versatile applications such as logic gates, supramolecular systems, liquid crystals, and super-resolution imaging because of their outstanding bistability and fatigue resistance. However, for typical diarylethene systems, there always exist three typical unsolved issues. The first is how to modulate the bistability between the open and closed forms from the viewpoint of ethene bridge aromaticity. The second is how to decrease and avoid the photoinactive parallel conformer in order to achieve a high quantum yield, since the open form possesses the photoactive antiparallel (ap) conformation and the photoinactive parallel (p) conformation. Because of the typical rapid rotation of the flexible side aryl groups, the two conformers cannot be separated efficiently, thereby resulting in a relatively low photocyclization quantum yield. The third is how to fulfill the enantiospecific transformation with reversibility to photomodulate the chirality. Stereochemically, the ap conformer with C2 symmetry can be further subdivided into a pair of enantiomers with P and M helicity originating from the central hexatriene moiety. Similarly, the rapid rotation can also lead to the loss of intrinsic chirality, restricting the development and application of light-driven chiroptical switches. Accordingly, it is desirable to construct a specific diarylethene system to break through these bottlenecks for real versatile applications.Our group has recently developed a unique sterically hindered diarylethene system based on benzobis(thiadiazole) as the ethene bridge for completely solving these issues. We introduce a low-aromaticity benzobis(thiadiazole) unit into the diarylethene as a central ethene bridge with incomparably high bistability. To block or freeze the rotation of flexible side aryls, we further incorporate a large bulky benzothiophene unit to induce a large steric hindrance, or rotation barrier, between the ethene bridge and side aryls, thereby successfully separating multiple conformers of the diarylethenes with high photocyclization quantum yields and enantiospecific photoreaction. Consequently, given such a fantastic building block, we enhance its performance by means of supramolecular self-assembly, thereby realizing unique conformer-dependent self-assembly as well as unprecedented concerted isomerization and enantiospecific photoreaction of photoresponsive metallacycles. In addition, decoration of the intrinsically chiral diarylethenes with mesogenic units can enable us to manipulate the helical superstructure of liquid crystals, thus achieving a multiple anticounterfeiting technique and a quadridimensional manipulable laser. We also unravel the dual aggregation-induced emission (AIE) behavior of the sterically hindered diarylethene, especially as applied in super-resolution imaging.

Secondary metabolites of the leaves of Tricalysia atherura N. Hallé (Rubiaceae) and their potential antiplasmodial activity

One monoterpene indole alkaloid, atheruramine (1) bearing an ether bridge linking, one hydrobenzoin derivative, tricalydioloside (2) and two ursane-type triterpenes, atherurosides (A and B) (3 and 4) were isolated from the leaves of Tricalysia atherura, together with eight known compounds. The structures of these new compounds were elucidated on the basis of the results of spectroscopic analysis, and the relative configurations of compounds 1–3 were established by NOE difference. Four of the metabolites were screened in vitro against both chloroquine (CQ)-sensitive (3D7) and -resistant (Dd2) strains of Plasmodium falciparum; they were found to exhibit moderate activity against chloroquine-resistant (Dd2) (IC50 64.99–92.29 μg/mL). Meanwhile, crude extract possesses high antiplasmodial activity against both 3D7 and Dd2 strains of P. falciparum (IC50 4.39–7.54 μg/mL) and high selectivity indices values (SI > 10) and was found to be safe.

Triphenylamine-based highly active two-photon absorbing chromophores with push-pull systems

Two triphenylamine-based star-type push-pull chromophores (T1, T2) were designed and synthesized. Triphenylamine serves as the central core and acts as an electron-donating group surrounded by electron-withdrawing pentafluorobenzene or N,N-dimethyl substituted tetrafluorobenzene, which are connected by ethylene bridges. Single-crystal X-ray diffraction confirmed the structures and molecular arrangement of two chromophores. The systematic photophysical research of T1 and T2 absorption characteristics was carried out to gain a better understanding of how structure-property relationships affect the observed nonlinear optical absorption phenomenon. Complementary calculations based on density functional theory (DFT) further confirmed the experimental results. Both chromophores exhibited excellent two-photon absorption (TPA) properties in CH2Cl2. Notably, T2 has more remarkable nonlinear optical absorption effects with the TPA cross-section up to 4.24 × 107 GM. By adjusting the electronic structures of the chromophores through introducing pentafluorobenzene or N,N-dimethyl as functional groups with different electron-donating or withdrawing behaviors, the TPA performance of the small organic molecule could be greatly enhanced. These molecular structures with push-pull systems were excellent candidates for different two-photon applications.

The Puzzling Question about the Origin of the Second Electron in the Molecular Photocatalytic Reduction of CO2

AbstractHerein, a new supramolecular photocatalyst RuRe3 containing three Re(dmb)CO3Cl (dmb=4,4‘‐dimethyl‐2,2‘‐bipyridine) (Re) building blocks connected through an ethylene bridge to one [Ru(dmb)3]2+‐unit (Ru) is presented. We investigated the photophysical properties of this novel tetranuclear complex and compared these to compounds with one (RuRe) and two (RuRe2) catalytic units. Under irradiation, all three photocatalysts exhibit high activity and photostability for the reduction of CO2 to CO, with RuRe3 achieving the highest turnover number (11800) reported to date for a Re(I)/Ru(II)‐containing homogeneous catalyst. This tetranuclear complex is especially superior at small catalyst concentrations, which is attributed to an efficient second electron transfer via an intramolecular mechanism. Intermolecular electron transfer from small and mobile Re to RuRe motifs are found to also increase the catalytic performance of the system to a similar level (turnover number=12100). These synergistic effects are attributed to an improved catalytic cycle, stabilizing the bi‐ and tetrametallic complexes by providing the electrons quickly and effectively. Since the second electron provision is not finally clarified for molecular systems until today, our photocatalytic studies present important insights into this crucial step. Further, these investigations should be considered for the design and synthesis of new and efficient supramolecular CO2‐reducing photocatalysts.