Bridging Chain Research Articles

Copper(II) complexes of hindered diazines: methylquinoxalines

Five new copper(II) complexes of substituted quinoxaline ligands have been prepared and characterized via single crystal X-ray diffraction, including [Cu(5-Mequinox)2(NO3)2] (2), [Cu(5-Mequinox)(NO3)(H2O)(μ-1,3-NO3)]n (3), the chloride salt (5-MequinoxH)2[Cu3Cl8] (4), the complex [Cu(6-Mequinox)2(NO3)2] (5) and [(2-carboxylato-3-methylquinox)(2-hydroxymethyl-3-methylquinox)nitratocopper(II)]. CH3CN (6) [quinox = quinoxaline; 5-Mequinox = 5-methylquinoxaline; 6-Mequinox = 6-methylquinoxaline]. None of the complexes produced diazine bridged chain structures (as seen in [(quinox)Cu(NO3)2]n (1)), although 3 forms chains via a bridging nitrate ion. Crystal packing is controlled primarily through hydrogen bonding and π-stacking of nitrate ions. The temperature dependent magnetic susceptibility data of the parent compound [(quinox)Cu(NO3)2]n are also reported and discussed.

Photocurable vitrimers with malleable and self-healing trade-off enabled by manipulating dynamic boronic ester bonds

Although numerous strategies refer to dynamic covalent bond exchanges of small molecules for self-repairing thermosets, it remains a critical challenge to be able to jointly tune the malleability and dynamic properties of photocurable materials via extending dynamical small molecule bridging chains with tunable kinetic features. Herein, we successfully synthesized two typical diboronic ester molecules (diboronic ester dithiol/diacid) with variable dioxaborolane metathesis kinetics, which acted as dynamical interlinking segments constructing simple hydrogenated bisphenol A (HBA) epoxy backbone to achieve dynamically cross-linking feature. Subsequently, the acrylate- and anhydride-modified HBA vitrimers bearing diboronic ester-extending segment variants and photocuring traits are successfully synthesized by a one-pot reaction. Consequently, it is demonstrated that the embedded amounts of dynamic diboronic ester bonds in the backbone play a key role in the photopolymerization rate of photocurable vitrimers. The photopolymerization rate decreases significantly as more diboronic ester segments. Moreover, the diboronic ester dithiol-mediated photocurable vitrimer (HBA-S) exhibits enhanced malleability (strain at break of 26.6 %), desirable photo-crosslinked network, and accelerated thermal-triggered self-healing ability (scratch self-healing efficiency of closing to 100 % at 150 °C), compared to those of the diboronic ester diacid-mediated vitrimer (HBA-O) under identical conditions. This work validates the probability of transferring the dioxaborolane metathesis of small molecules to dynamic properties of bulk UV-curing materials, which provides valuable guidance for the rational design and fabrication of tunable dynamic photocurable materials.

Electronic dynamics of donor–bridge–acceptor system with a bridge impurity incorporated in dissipative environments

Electronic dynamics of Donor–Bridge–Acceptor system with a bridge impurity incorporated in dissipative environments is studied taking advantage of the quasi-adiabatic propagator path integral approach in this article. An impurity site is introduced in the center of bridge chain of the system. The numerical calculations indicate the electron transfer rates of the system are changed when the energy gap between the center site (impurity site) and other bridge sites increased from −2.5 to 2.5 eV, the relaxation rates decrease and the dephasing rates increase as the energy gap increases, respectively under the same environment factors (e.g. temperature and system–environment coupling). However, the electron transfer mechanism of the system is hardly affected when the bridge impurity energy is increased in the range of ±21% relative to the other bridge energy, and the occupation populations of bridge chain are not more than 10%, which means the superexchange mechanism also works well within the context of this study.

Synthesis of Halogenated Dibenzo[1,2,6]triazonines and Late-Stage Functionalization of the Triazonine Ring.

Dibenzotriazonine represent a new class of nine-membered cyclic azobenzenes with a nitrogen atom embedded in the bridging chain. To enable future applications of this photoactive backbone, we propose in this study the synthesis of mono- and dihalogenated triazonines, that allow the late-stage introduction of different functionalized aryl groups and heteroatoms (N, O, and P) via palladium-catalyzed reactions. Indeed, different diphenylphosphoryl-triazonines were synthesized with functional groups such as aniline or phenol. Bis(diphenylphosphoryl)phenyl mono- and bis-carbamate-triazonines were also isolated in good yields.

Paddlanes revisited: Which are the smallest possible?

AbstractPaddlanes are tricyclic molecules with four bridging chains that share the same two bridgehead carbon atoms. The smallest known paddlane containing only carbon atoms in the main framework has a total of 18 atoms. We utilized computational chemistry (MP2/cc‐pVTZ) to locate the smallest possible all‐carbon paddlanes that meet the criterion suggested by Hoffmann, Schleyer, and Schaefer as being “fleeting,” meaning frequency calculations suggest the structures are energy minima on their respective potential energy surfaces (PES). Our results suggest that paddlane compounds with a total of 10 or fewer atoms can be considered to be non‐viable either because they are not energy minima on the PES or due to strain in the system that manifests as especially long carbon–carbon bonds. Some paddlanes with a total of 11 carbon atoms proved to be energy minima but still exhibited longer carbon–carbon bonds than normal. Finally, several paddlanes with a total of 12 carbons appear to be the least strained since carbon–carbon bond lengths remain reasonable.

Mechanical reinforcement by bridging chains in polymer nanocomposites

The adsorption-induced bridging of polymer chains between adjacent nanoparticles was studied in poly(vinyl acetate)/silica nanocomposites with different polymer molecular weights, interaction strengths, nanoparticle sizes, and silica loading fractions. The polymer bridging contribution is successfully decoupled from the apparent rubbery plateau modulus by subtracting the hydrodynamic and trapped chain entanglement contributions. The bridging modulus depends on the nearest interparticle surface distance through a power-law relation with a universal exponent −3. Polymer molecular weight can enhance the bridging modulus only when nanoparticles have a high density of adsorption sites due to the emergence of direct bridging of multiple particles by one chain in addition to the regular bridging through self-similar carpets. Our results illustrate that bridging chains can dominate modulus enhancement at nanoparticle's loading at about 10 vol% in polymer nanocomposites with long polymer chains and high surface silanol density.

Hydrophilic Photocrosslinkers as a Universal Solution to Endow Water Affinity to a Polymer Photocatalyst for an Enhanced Hydrogen Evolution Rate.

A universal approach for enhancing water affinity in polymer photocatalysts by covalently attaching hydrophilic photocrosslinkers to polymer chains is presented. A series of bisdiazirine photocrosslinkers, each comprising bisdiazirine photophores linked by various aliphatic (CL-R) or ethylene glycol-based bridge chains (CL-TEG), is designed to prevent crosslinked polymer photocatalysts from degradation through a safe and efficient photocrosslinking reaction at a wavelength of 365nm. When employing the hydrophilic CL-TEG as a photocrosslinker with polymer photocatalysts (F8BT), the hydrogen evolution reaction (HER) rate is considerably enhanced by 2.5-fold compared to that obtained using non-crosslinked F8BT photocatalysts, whereas CL-R-based photocatalysts yield HER rates comparable to those of non-crosslinked counterparts. Photophysical analyses including time-resolved photoluminescence and transient absorption measurements reveal that adding CL-TEG accelerates exciton separation, forming long-lived charge carriers. Additionally, the in-depth study using molecular dynamics simulations elucidates the dual role of CL-TEG: it enhances water penetration into the polymer matrix and stabilizes charge carriers after exciton generation against undesirable recombination. Therefore, the strategy highlights endowing a high-permittivity environment within polymer photocatalyst in a controlled manner is crucial for enhancing photocatalytic redox reactivity. Furthermore, this study shows that this hydrophilic crosslinker approach has a broad applicability in general polymer semiconductors and their nanoparticulate photocatalysts.

A mathematical model of thermoplastic elastomers for analysing the topology of microstructures and mechanical properties during elongation

In this study, a mathematical model based on graph theory is developed to analyse the deformed structures and mechanical properties of thermoplastic elastomers (TPEs) using ABA-type triblock copolymers. TPEs exhibit a network structure formed by bridge chains; deformation of this network structure causes stress. During the deformation of TPEs, domain breakage and coalescence occur, accompanied by topological changes in the chains, such as conformational transitions between the bridge and loop chains. By employing the mathematical concepts of harmonic realization of graphs in the physical space and the tension tensor to quantify the stress in the bridge-chain network structure, an effective method for analysing topologicalchanges in microstructures caused by elongation is proposed. As an application of this method, optimal geometric structures of block copolymers with desired functionalities can be determined.

Identification of a carbohydrate recognition motif of purinergic receptors.

As a major class of biomolecules, carbohydrates play indispensable roles in various biological processes. However, it remains largely unknown how carbohydrates directly modulate important drug targets, such as G-protein coupled receptors (GPCRs). Here, we employed P2Y purinoceptor 14 (P2Y14), a drug target for inflammation and immune responses, to uncover the sugar nucleotide activation of GPCRs. Integrating molecular dynamics simulation with functional study, we identified the uridine diphosphate (UDP)-sugar-binding site on P2Y14, and revealed that a UDP-glucose might activate the receptor by bridging the transmembrane (TM) helices 2 and 7. Between TM2 and TM7 of P2Y14, a conserved salt bridging chain (K2.60-D2.64-K7.35-E7.36 [KDKE]) was identified to distinguish different UDP-sugars, including UDP-glucose, UDP-galactose, UDP-glucuronic acid, and UDP-N-acetylglucosamine. We identified the KDKE chain as a conserved functional motif of sugar binding for both P2Y14 and P2Y purinoceptor 12 (P2Y12), and then designed three sugar nucleotides as agonists of P2Y12. These results not only expand our understanding for activation of purinergic receptors but also provide insights for the carbohydrate drug development for GPCRs.

A simplified pore-scale model for slow drainage including film-flow effects

Liquid-filled corners and capillary bridges can establish networks connecting seemingly isolated clusters during drainage in porous media. Coupled with drainage through the bulk of pores and throats, the flow through these networks constitutes a secondary drainage mechanism that can significantly affect fluid configurations and residual saturations. In order to investigate the prevalence of this drainage mechanism, we propose a quasi-static pore-network model based on modifying the trapped-cluster-identification algorithm in an invasion-percolation model. With the modification, wetting-phase connectivity is provided by direct successions of pores and throats, represented by sites and bonds, as well as by chains of interconnected capillary bridges. The advancement of the fluid interface in the porous matrix is determined by the bonds’ invasion thresholds and local capillary pressure values, calculated taking into consideration gravitational effects. With the proposed model, experimentally verified phenomena related to slow drainage in granular porous media are reproduced, showing good qualitative agreement.

Research progress of oxazole derivatives in the discovery of agricultural chemicals

AbstractThe search for new scaffolds is one of the important goals in the discovery of new pesticides, and the oxazoles as an important five‐membered heterocyclic compound are widely used in the discovery of new pesticides. Oxazoles ring are often used as the scaffolding structure or bridging chain to connect different reactive groups. In recent years, oxazoles have made rapid progress in the discovery of new pesticides, especially in the discovery of fungicides, insecticides, and acaricides. A systematic review of the recent research progress of oxazoles in the discovery of new pesticides is of interest. Therefore, we comprehensively reviewed the application of oxazole compounds in the discovery of new pesticides from 2003 to 2023; summarized the fungicidal, antibacterial, insecticidal, acaricidal, and herbicidal activities of oxazoles; and discussed the structure–activity relationship, physiochemical and mechanism of action, with the aim of providing inspiration and ideas for the discovery of oxazoles as novel agrochemicals.

A Zn-based Zig-Zag 1D chain type coordination polymer for removal of methylene blue dye from an aqueous solution

A 1D zig-zag zinc coordination chain, [Zn(piv)2]n (1) (where piv = pivalic acid) has been synthesized by a reaction of ZnCl2 with O-donor pivalic acid in the mixed solvent system (MeCN/MeOH) and structurally characterized via ultraviolet–visible spectroscopy (UV), Fourier transform infrared (FT-IR) spectroscopy, elemental analysis, and X-ray crystallography. The crystal structure is a bridging chain of zinc metal connected via pivalic acids. The synthesized coordination polymer was explored for photochemistry to study photoluminescence and photocatalytic properties. The photocatalytic properties were investigated against methylene blue (MB) dye under UV light illumination. Under optimal reaction conditions (catalyst dosage = 10 mg, initial concentration of dye = 20 mg/L, pH = 9) the maximum photodegradation of methylene blue was found to be 72.56% in 120 min illumination time. The photocatalytic reaction showed pseudo-second-order kinetics with a rate constant of 0.012 L.mg−1.min−1. Furthermore, the recyclability test showed that compound 1 retained its photocatalytic potential even after five successive uses. The compound 1 could be a proficient and economical choice for the photocatalytic elimination of pollutants from wastewater.

Stress Chain Analysis for an ABA Triblock Copolymer Using Principal Component Scores.

Researchers characterize the mechanical properties of ABA triblock copolymers by structures such as chain conformation. During elongation, bridge chains are stretched and act as a stress chain. Some loop chains also act as a stress chain because of the transmission of stress through an entanglement of loop chains. The stress chain, including the entangled loop chains, in an ABA triblock copolymer that exhibits a body-centered cubic structure was analyzed by principal component analysis (PCA), using the physical data for the B block obtained by coarse-grained molecular dynamics simulations. Local deformation of the A domains caused by the stress chains was also analyzed by PCA of the A block. The dynamics of the stress chain strongly corresponded to the recombination of the A domains; shrinkage because of domain breakage, replacement of stress chains, and biased stress distribution as well as its time dependence were observed.

Enantioselective Synthesis of Planar Chiral Macrocyclic Metacyclophanes by Pd-Catalyzed C–O Cross-Coupling

Despite the presence of planar chiral elements in natural products and in ligands for asymmetric catalysis, catalytic enantioselective methods for installing planar chirality remain underdeveloped relative to methods for installing central and axial chirality. Here, we report an enantioselective Pd-catalyzed C–O bond-forming macrocyclization to access enantioenriched planar chiral macrocyclic metacyclophanes incorporating 2,3,4-trisubstituted pyridines. A variety of bridging chains and substituents can be incorporated in the metacyclophanes under the same reaction conditions (14 examples, 59–85% yields, 79–92% ee) to generate enantioenriched meta-, metaortho-, and metapara- cyclophanes. The syn-/anti-conformational preferences of metacyclophanes were elucidated by the X-ray structures, 1H NMR analyses, and computational studies. We also found that the two enantiomers of the metacyclophane can be obtained using the same enantiomer of the chiral ligand by starting from two regioisomeric linear precursors. This work provides an entry into the design of enantioselective cross-coupling macrocyclizations to access planar chiral structures for applications in medicinal chemistry and catalysis.

Terpyridine ruthenium–triarylamine asymmetrical mixed-valence systems: Syntheses, (Spectro) electrochemistry and theoretical calculations

A series of asymmetrical terpyridine ruthenium-TAA redox-active organometallic complexes was prepared and characterized. The bonding and electronic properties of these complexes were investigated by spectro-electrochemistry and theoretical calculations. Electrochemical results revealed that four complexes exhibited two successive single-electron redox processes, in which the first-step electrochemical behavior of tpyRu-ethynyl-TAA complexes occurred at the triarylamine moiety, the first-step based-metal oxidation of Cl-tpyRu-TAA complex was decided, and their half-wave potential difference ∆E decreased gradually. The near-infrared (NIR) spectroscopic results of mixed-valence states obtained by spectro-electrochemistry showed that they all have NIR multiple absorption characteristics. The maximum absorption wavelength of singly-oxidized tpyRu-ethynyl-TAA molecules redshifted with bridge conjugate extension, whereas Cl-tpyRu-TAA mixed-valence state only displayed weak absorption at high-energy region, as later confirmed by TDDFT calculation. The electron coupling parameters Hab obtained from the inter-valence charge transfer analysis of mixed-valence states by the Marcus–Hush theory decreased gradually with the extension of the bridge chain, consistent with the electrochemical results. In addition, DFT calculation reflected that the HOMO contribution in bridge chain of neutral molecules increased with the conjugate bridge extension, and the spin density distribution of mixed-valence states was mainly localized on the aryl bridge and NAr2 and featured the less metal character and hence less charge delocalization. The above results concluded that the degree of electronic coupling and the order of redox processes are greatly affected by conjugated bridge and the coordination model between terpyridine and ruthenium.

3D host-guest material of {Ag(pz)} modified {BW12O40} with supercapacitor, photocatalytic dye degradation and H2O2 sensing performances

The synthesis and properties of inorganic-organic hybrids based on {BW12O40} are still the focus of polyoxometalates. Here, 3D host-guest material with the molecular formula [Ag5(pz)6(H2O)4][BW12O40] (pz ​= ​pyrazine) (1) was synthesized by the hydrothermal method. The single crystal analysis showed that the compound was composed of a [Ag3(pz)4]3+ fragment, a [Ag2(pz)2(H2O)4]2+ fragment, and a [BW12O40]5- anion. In the structure, Ag ions are connected into 1D wavy linear bridge chains by pz ligands to form {Ag-pz}n. Twelve Ag ions form a large loop via pz, and each loop forms a supramolecular 2D structure with two {BW12O40} and forms a 3D structure through supramolecular interaction. In the three-electrode system with compound 1 as the active substance and nickel foam as the collector, the specific capacitance is 245.6 ​F ​g−1 when the current density is 1 ​A ​g−1. Higher than those reported in the literature. Constitute a symmetric two-electrode system, with an energy density of 6.9 ​Wh kg−1, with a power density of 498.7 ​W ​kg−1. And after 5000 cycles, the specific capacitance remains at 92.5%. Besides, the photocatalytic degradation rates of methylene blue (MB), methyl orange (MO), and rhodamine B (RhB) were 93.2% and 90.0%, and 93.7%, respectively. Good sensing performance for H2O2, with a wide linear range (5 μ M-0.27 ​mM) and low detection limit (2.2 μ M).

Conversion of low temperature coal tar into high value-added chemicals based on the coupling process of fast pyrolysis and catalytic cracking

To convert the Xinjiang low temperature coal tar (XJ-CT) into high value-added chemicals, the coupling process of fast pyrolysis and catalytic cracking (FP-CC process) is proposed, and the related fundamental data is collected in this research. First, the composition of XJ-CT is analyzed by GC-GC/MS, and the result shows that the relative contents of alkanes, alkenes, aromatics, and the oxygen compound are 13.16%, 4.85%, 48.38%, and 29.29%, respectively. Then, the performance of XJ-CT fast pyrolysis is evaluated under different reaction temperature. The results show that aromatics is predominant among the pyrolysis vapor, whereas the yield of aliphatic products enhances with the increase of temperature. And the aliphatic products are mainly formed from the deep cleavage of long-chain aliphatics and alkyl side chains (alkyl bridge chain) of aromatics. Meanwhile, the relative content of oxygen-containing compounds decrease with the increase of temperature. Furthermore, molecular distributions of the major groups in pyrolysis vapor with different temperatures are summarized to gain insight into the pyrolysis process. Finally, the ZSM-5 (40), ZSM-5 (200), and USY zeolite are used to catalyze the pyrolysis vapor. It is demonstrated that the maximum light olefin yield of 31.79% is obtained over ZSM-5 (40), while converting XJ-CT to liquid fuels can be realized on USY zeolite.

A fungal-modified material with high uranium (VI) adsorption capacity and strong anti-interference ability.

With open-chain polyether as the bridge chain, a new fungal-modified material with diamidoxime groups was prepared by a series of uncomplex synthesis reaction. The orthogonal experiment obtained its optimized adsorption conditions as follows: the initial pH value of 6.5, the initial uranyl concentration of 40mg L-1, the contact time of 130min, and the a solid-liquid ratio of 25mg L-1. The maximum adsorption capacity of target material was 446.20mgg-1, and it was much greater than that of the similar monoamidoxime material (295.48mgg-1). The linear Langmuir (R2 = 0.9856) isotherm models and the linear pseudo-second-order kinetic model (R2 = 0.9931) fit the experimental data of uranium (VI) adsorption better, indicating the adsorption mechanism should mainly be the monolayer adsorption and chemical process. In addition, the relevant experiments exhibited the prepared material had the good reusability, which reached 84.25% of the maximum capacity after five cycles, and the excellent anti-interference performance. The above features suggest the modified fungus material will have the good application prospect in the future.

Investigation the effect of π bridge and side chain on photovoltaic properties of benzodithiophene and quinoxaline based conjugated polymers

A series of donor–acceptor type alternative polymers containing 2D-BDT and 1D-BDT as the donors and quinoxaline as the acceptor were successfully obtained by Stille coupling reactions. Synthesized polymers containing selenophene and thiophene as π-bridges in their backbones and 2-ethylhexylselenophene and 2-ethylhexylalkoxy side groups on the BDT structure were named as P1, P2, P3 and P4, respectively. Eonsetox and Eonsetred were investigated for P1, P2, P3, and P4, respectively. Onset oxidation potentials and onset reduction potentials for P2 and P4 containing selenophene π-bridge in their structure were measured at lower levels than P1 and P3 containing thiophene π-bridge. Maximum absorptions for P1 and P2 containing 2D-benzodithiophene were observed at 595 nm and 610 nm, while maximum absorption peaks were observed at 575 nm and 610 nm for P3 and P4 polymers. It was observed that the absorption onset of P2 and P4 polymers containing selenophene π bridges were relatively red-shifted to 735 nm and 732 nm, respectively. According to the kinetic studies, the maximum optical contrast was observed in the bipolaron region for all polymers and was measured as 57% for P1 and P2, 52% for P3, and 55% for P4, respectively. Theoretical calculations were executed on model tetramer structures to shed light on how changing the π-bridge and substituent on benzodithiophene along the building block influenced the electronic, structural and optical properties of the designed polymers. All polymers were used as electron rich donor materials for bulk heterojunction organic solar cells with ITO/PEDOT:PSS/Polymer:PC71BM/LiF/Al device architecture. P3-based solar cell device resulted the highest power conversion efficiency as 4.47% with VOC, JSC and FF values of 0.80 V, 10.08 mA/cm2 and 55.5%, respectively.

Biophysical Evaluation and In Vitro Controlled Release of Two Isomeric Adamantane Phenylalkylamines with Antiproliferative/Anticancer and Analgesic Activity.

The aqueous dissolution profile of the isomeric synthetic adamantane phenylalkylamine hydrochlorides I and II was probed. These adducts have shown significant antiproliferative/anticancer activity associated with an analgesic profile against neuropathic pain. They are both devoid of toxic effects and show appreciable enzymatic human plasma stability. The structures of these two compounds have been elucidated using 2D NMR experiments, which were used to study their predominant conformations. Compound II’s scaffold appeared more flexible, as shown by the NOE spatial interactions between the alkyl bridge chain, the aromatic rings, and the adamantane nucleus. Conversely, compound I appeared very rigid, as it did not share significant NOEs between the aforementioned structural segments. MD simulations confirmed the NOE results. The aqueous dissolution profile of both molecules fits well with their minimum energy conformers’ features, which stem from the NOE data; this was nicely demonstrated, especially in the case of compound II.