Quinone Units Research Articles

1,4,5,8-tetrasubstituted dihydroanthracene-based triptycene trisquinones: Synthesis, structural, and physicochemical characterization

1,4,5,8-tetrasubstituted dihyroanthracene-based triptycene trisquinones (TT) molecules, THAO-TT and tris(THAO)-TT, were synthesized by Diels–Alder reaction between TT and 1,4,5,8-tetrakis(hexyloxy)anthracene to produce the extended triptycene derivatives containing electron-accepting functionality. The prepared THOA-TT and tris(THOA)-TT exhibited excellent thermal stability owing to the rigid TT framework. The optical and redox properties of THOA-TT and tris(THOA)-TT were controlled by the homoconjugation between the benzoquinone units and the peripheral units through the connecting methine groups.

Superhydrophobic biochars as catalysts for efficient hydrogen transfer in N-heterocycles and nitrobenzene reactions

The heteroatom-doped carbon nanomaterials can be the active catalysts in hydrogen transfer reactions, however, carbon-catalyzed hydrogen transfer processes in the absence of additives and cocatalysts have been rarely described. Herein, functional biochar catalysts (FBCs) were successfully fabricated from wheat straw by a simple scalable two-step strategy via reconstructing the catalytic active sites in carbon precursors and subsequently controlled carbonization. The characterization of FBCs was discussed with regard to morphologic structures, chemical constitutions and performance, revealing that the high hydrophobicity is beneficial for obtaining high activity. Wherein the optimized FBC-850 catalyst exhibited high activity and durability toward the reaction of N-heterocycles and nitrobenzene in the aqueous systems due to the synergistic effects that were attributed to the external superhydrophobicity, internal capillary repulsion and hydrogen transfer property, eliminating the need for additional co-catalysts or additives. In the model reaction, the yields of quinoline and aniline were respectively achieved at 92% and 90%. Furthermore, the encapsulated quinone units as the active sites in FBC-850 formed the bipyramidal structure, enabling the hydrogen transfer process through a cyclical hydrogen exchange, which was proved from kinetic studies combined with spectral characterization and theoretical calculation. In addition, a possible reaction mechanism was proposed based on the observation of key intermediates and DFT calculations, also providing a rationale for the existing active site structures.

Self‐doped conjugated polymers with electron‐deficient quinone units for enhanced electron transport in highly efficient organic solar cells

AbstractOrganic solar cells (OSCs) have attracted significant attention as a burgeoning flexible technology, owing to their advanced power conversion efficiencies. Moreover, interface materials play a crucial role in optimizing energy level alignment between the active layer and electrodes, thereby enhancing carrier extraction within the device and improving efficiency. However, current methodologies for fabricating electron‐transport materials with superior mobility are still limited compared with those for hole‐transport materials. In this study, a benzodifurandione (BFDO)‐derived building block with quinone resonance property and strong electron‐withdrawing capability was synthesized. Two conjugated polymers, namely PBFDO‐F6N and PBFDO‐F6N‐Br, were prepared, both of which exhibited good electron mobility and exceptional interface modification capabilities. A comprehensive investigation of the interaction between the interface layer and the active layer revealed that PBFDO‐F6N induced doping at the acceptor interface. Additionally, the high mobility of PBFDO‐F6N facilitated efficient carrier extraction at the interface. Consequently, the application of PBFDO‐F6N as the cathode interface layer for PM6:BTP‐eC9‐based OSC devices resulted in a remarkable efficiency of 18.11%. Moreover, the device efficiency remained at ∼96% even at a PBFDO‐F6N interface thickness of 50 nm, demonstrating the great potential of this material for large‐scale device preparation.

The Synthesis and Reactivity of Naphthoquinonynes

AbstractThe first systematic exploration of the synthesis and reactivity of naphthoquinonynes is described. Routes to two regioisomeric Kobayashi‐type naphthoquinonyne precursors have been developed, and the reactivity of the ensuing 6,7‐ and 5,6‐aryne intermediates has been investigated. Remarkably, these studies have revealed that a broad range of cycloadditions, nucleophile additions and difunctionalizations can be achieved while maintaining the integrity of the highly sensitive quinone unit. The methodologies offer a powerful diversity oriented approach to C6 and C7 functionalized naphthoquinones, which are typically challenging to access. From a reactivity viewpoint, the study is significant because it demonstrates that aryne‐based functionalizations can be utilized strategically in the presence of highly reactive and directly competing functionality.

The Synthesis and Reactivity of Naphthoquinonynes.

The first systematic exploration of the synthesis and reactivity of naphthoquinonynes is described. Routes to two regioisomeric Kobayashi-type naphthoquinonyne precursors have been developed, and the reactivity of the ensuing 6,7- and 5,6-aryne intermediates has been investigated. Remarkably, these studies have revealed that a broad range of cycloadditions, nucleophile additions and difunctionalizations can be achieved while maintaining the integrity of the highly sensitive quinone unit. The methodologies offer a powerful diversity oriented approach to C6 and C7 functionalized naphthoquinones, which are typically challenging to access. From a reactivity viewpoint, the study is significant because it demonstrates that aryne-based functionalizations can be utilized strategically in the presence of highly reactive and directly competing functionality.

Polyarene Oxides with Tunable Quinone Units for Photocatalytic CO2 Reduction: A Simple Strategy toward Effective and Selective Catalysts.

The photocatalytic transformation of carbon dioxide (CO2) into valuable chemicals is a challenging process that requires effective and selective catalysts. However, most polymer-based photocatalysts with electron donor-acceptor (D-A) structures are synthesized with a fixed D-A ratio by using expensive monomers. Herein, we report a simple strategy to prepare polyarene oxides (PAOs) with quinone structural units via oxidation treatment of polyarene (PA). The resultant PAOs show tunable D-A structures and electronic band positions depending on the degree of oxidation, which can catalyze the photoreduction of CO2 with water under visible light irradiation, generating CO as the sole carbonaceous product without H2 generation. Especially, the PAO with an oxygen content of 17.6% afforded the highest CO production rate of 161.9 μmol g-1 h-1. It is verified that the redox transformation between quinone and phenolic hydroxyl in PAOs achieves CO2 photoreduction coupled with water oxidation. This study provides a facile way to access conjugated polymers with a tunable D-A structure and demonstrates that the resultant PAOs are promising photocatalysts for CO2 reduction.

A semi-solid, polychromatic dual-band electrochromic smart window: Visualizing sunlight and solar heat transmission

In this paper, a novel semi-solid, polychromatic dual-band electrochromic smart window was constructed by organically assembling monoclinic WO3-x nanowires (m-WO3-x NWs), AlCl3-polyvinyl alcohol (PVA) and polyaniline (PANI). The device not only presented the independent regulation of “bright”, “cool” and “dark”, but also exhibited excellent comprehensive performance, including large optical modulation (74.9 % and 79.1 % at 700 and 2000 nm, respectively.), short coloring/bleaching times (7.6/2.7 and 6.7/3.9 s at 700 and 1200 nm, respectively), and good stability and reversibility (the capacity decreased by 4.3 % and the coulombic efficiency stabled at 99.2 % after 1000 cycles). In addition, the multi-colored PANI endowed the window with the ability to visually monitor modulation modes, as well as indoor sunlight and thermal transmittance. The transparent, green, and blue represented “bright”, “cool”, and “dark” modes, and the depth of the color stood for the control effect in a certain mode. Moreover, the dual-band modulation and polychromatic conversion mechanisms of individual electrodes and the smart window prototype were also elucidated in detail. The modulation of near-infrared light mainly comes from the localized surface plasmon resonance (LSPR) absorption and the phase transition of m-WO3-x NWs, as well as the generated polarons and bipolarons of PANI. While the selective absorption of visible light was related to the bandgap transition of m-WO3-x NWs and the electronic transition of the quinone unit. Surprisingly, the smart window could achieve a maximum decrease of 4.3 °C by controlling the “bright-dark” mode transition in real application simulations, significantly boosting the process of low carbon environmental protection and the construction of energy-saving buildings.

Separation of cyclohexanol from cyclohexanol/cyclohexene mixtures by crystals of pillar[6]arene containing three benzoquinone units.

Here, we develop a new absorbent for efficient separation of cyclohexanol (CHA-ol) and cyclohexene (CHA-ene) by using crystals of pillar[6]arene with three benzoquinone units (P3QA). P3QA crystals are found to show remarkable selectivity for CHA-ol in 50 : 50 (v/v) CHA-ol : CHA-ene mixtures with a purity of 95.2%, along with vapochromic behavior.

Electron-withdrawing quinone polymers with enhanced conjugated planarity for n-type organic thermoelectrics

A new electron-withdrawing quinone unit was developed for n-type thermoelectrics. Two n-type polymers were constructed, and the polymer with selenophene exhibited enhanced planarity and better thermoelectric performance.

Modulating conjugated microporous polymers via cyclization as a remarkable photo-enhanced uranium recovery platform

Uranium recovery is of great significance for managing environmental contamination, improving the utilization rate of uranium resources, reducing the pressure of nuclear fuel supply and building a closed-loop nuclear fuel cycle system. However, most of the current adsorbents are limited in practical application due to their poor selectivity in highly acidic environments (pH = 1). Here, we present a powerful uranium recovery strategy with combined ligand complexation, chemical reduction and photoreduction based on metal-free cyclization-modulated conjugated microporous polymers (CMPs). Our well-tailored CMP (CTATP-DHBA) is rich in pyridine and hydroquinone units, forming favorable six-membered chelation motifs to be well suited for selective loading and reduction of UVI, thus exhibiting remarkable uranium removal efficiency (ca. 83.27% removal in 200 ppm solutions, pH = 1). In the dark, CTATP-DHBA can effectively reduce pre-enriched UVI to UIV in situ via hydroquinone units on the skeleton, thus weakening the proton competition and achieving excellent uranium recovery efficiency. Meanwhile, the synergistic effect of the cyclized π-conjugated skeleton and the oxidized benzoquinone units significantly enhances the photocatalytic activity of CTATP-DHBA, and an additional UVI photocatalytic reduction can occur under visible light irradiation, enabling photo-enhanced uranium recovery. Environmental ImplicationThe mineralization of valence-variable radionuclides such as uranium could not only enhance the extraction performance and simplify the subsequent separation procedure, but also effectively weaken the competition of protons for selective sites in the acidic sample matrix. Thus, the construction of robust CMPs with excellent photoreduction activity and affinity may be an ideal material for the selective extraction and in-situ mineralization of strategic nuclide uranium from strongly acidic radioactive wastewater. Herein, a metal-free cyclization-modulated CMP with the favorable six-membered chelation motifs is tailor-made as an efficient platform for efficient extraction and in situ mineralization of valence-variable nuclide uranium.

Tunable Supramolecular Ag+-Host Interactions in Pillar[n]arene[m]quinones and Ensuing Specific Binding to 1-Alkynes.

We developed an improved, robust synthesis of a series of pillar[6]arenes with a varying number (0-3) of quinone moieties in the ring. This easy-to-control variation yielded a gradually less electron-rich cavity in going from zero to three quinone units, as shown from the strength of host-guest interactions with silver ions. Such macrocycle-Ag2 complexes themselves were shown to display an unprecedented, sharp distinction between terminal alkynes, which strongly bound to such complexes, and internal alkynes, internal alkenes and terminal alkenes, which do hardly bind.

Selective Fluorescent Sensing for Iron in Aqueous Solution by A Novel Functionalized Pillar[5]arene.

Iron ion is one of the most physiologically important elements in metabolic processes, indispensable for all living systems. Since its excess can lead to severe diseases, new approaches for its monitoring in water samples are urgently needed to meet requirements. Here, we firstly report a novel and universal route for the synthesis of a series of pillar[n]arene derivates containing one benzoquinone unit by photocatalysis. With this in hand, an anthracene - appended water - soluble pillar[5]arene (H) with excellent fluorescence sensing potency was prepared. H enabled the ultrasensitive detection of iron ions in aqueous solution with limits of detection of 10-8 M. Over a wide range of metal ions, H exhibited specific selectivity toward Fe3+ . More importantly, H could still properly operate in a simulated sewage sample, coexisting with multiple interference ions.

Auxiliary coordination strategy designed poly(chloranil-squaricamide) cathode achieving enhanced specific capacity utilization and Zn2+ insertion/extraction for aqueous zinc ion batteries

High-performance organic cathodes with sustainable advantages are suitable for low-carbon and secure applications in aqueous zinc ion batteries (AZIB). Herein, we propose an improved auxiliary coordination facilitating Zn2+ insertion/extraction strategy to design a novel poly(chloranil-squaricamide) (PCSA) as AZIB cathode. The auxiliary coordination squaraine groups with appropriate Zn2+ coordination configuration can facilitate Zn2+ insertion/extraction, so that PCSA presents enhanced stable cycle performance and specific capacity utilization. Particularly, PCSA can perform maximum 98.4% specific capacity utilization and 93% capacity retention after 400 cycles under 0.02 A g−1, even under 0.1 A g−1 the capacity retention can still reach 80% after 1000 cycles. The ex-situ X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectra (FTIR) reveal that quinone units can undertake redox function in PCSA and the auxiliary coordination of the squaraine groups can facilitate Zn2+ insertion/extraction. The ex-situ XRD indicates that slight H+ is involved in the Zn2+ storage process. Such an auxiliary coordination strategy can provide a prospective design method to construct high-performance organic cathode materials for AZIB.

Electrochemistry and electrochemical assessment of host–guest complexation of substituted pillar[m]arene[n]quinones

Electrochemical behavior of pillar[n]arene[m]quinone (n + m = 5, n = 2–4) has been for the first time investigated in aqueous media on the glassy carbon electrode. All the compounds studied showed quasi-reversible redox conversion to hydroquinone derivatives. The reaction was not complicated with ionization of hydroxy groups or by the formation of intramolecular hydrogen bonds. In the whole pH region tested (2.0 – 9.0) the stoichiometry of electron and hydrogen ions transfer was found the same (1:1). The peak currents changed with no respect of the number of quinone units in the macrocycle molecule and were probably more affected by steric factors and self-aggregation confirmed by scanning electron microscopy. Adsorption of the macrocycles on the electrode covered with carbon black resulted in remarkable improvement of the conditions of electron exchange and of the peak currents on voltammograms. Screening of possible guest molecules showed that among amino acids, tyrosine formed complexes with pillarquinones both in solution and on the electrode interface. Complexation resulted in decrease of the peak currents on voltammograms due to steric hindrance of electric wiring. This made it possible to determine 5–100 µM tyrosine in the solution and 1–100 µM tyrosine with pillar[3]arene[2]quinone adsorbed in the carbon black layer. No interferences were established in normal human serum and Ringer-Locke’s solution. The approach to supramolecular detection of small molecules by intrinsic redox activity of the macrocyclic hosts can be extended to other analytes by modification of the macrocyclic components of the reaction.

Green electrospun poly(vinyl alcohol)/silicon dioxide nanofibrous membrane coated with polydopamine in the presence of strong oxidant for effective separation of surfactant-stabilized oil-in-water emulsion

Most nanofibrous membranes were electrospun from organic solutions. Because organic solvents are usually volatile and poisonous, they can cause unfavorable influence on the natural environment and human health. In this work, poly(vinyl alcohol)/silicon dioxide@polydopamine (PVA/SiO2@PDA) membrane was fabricated by green electrospinning of aqueous dispersion of PVA and SiO2 combined with deposition of PDA in the presence of strong oxidant sodium periodate. Notably, PDA coating with distinguished superhydrophilic and underwater superoleophobic property was obtained due to producing carboxyl components during degradation of quinone units. When the PVA/SiO2@PDA membrane was immersed in water, a stable hydrated layer produced on the membrane surface due to the presence of hydrophilic groups. The hydrophilicity of this hydrated layer could make water molecules pass through the membrane successfully and effectively prevent infiltration of oil droplets. This superhydrophilic and underwater superoleophobic membrane showed excellent oil/water separation performance for various oil-in-water emulsions. The maximum permeate flux reached 4413.96 L·m−2·h−1 with separation efficiency higher than 99.2 %. Moreover, excellent chemical stability as well as outstanding antifouling performance of the PDA-modified electrospun membrane provided long-term durability for oil/water separation. The developed PVA/SiO2@PDA membrane with superwetting property and good reusability exhibited prospective potential in the remediation of oily wastewater.

Donor-Acceptor Tribenzotriquinacene-Based Molecular Wizard Hats Bearing Three ortho-Benzoquinone Units.

Two π-extended bay-bridged tribenzotriquinacenes ("TBTQ wizard hats") 12 and 16 bearing three mutually conjugated, alternating veratrole-type and ortho-benzoquinone units were synthesized. The electronic properties of these complementarily arranged, nonplanar push-pull systems are affected by the fusion with the rigid, C3 -symmetric TBTQ core to a different extent, as revealed by X-ray structural analysis, UV-vis spectroscopy and cyclovoltammetry. The combination of three quinone units within the original TBTQ core and three veratrole-type bay bridging units in 12 gives rise to a more efficiently π-conjugated chromophore, as reflected by the shallower shape of wizard hat and its absorption in the visible up to 750 nm in comparison to 16. Congener 12 contains an aromatic 18-π electron system in contrast to the cross-conjugated analog 16. X-ray structure analysis of the precursor dodecaether 15 revealed the formation of a cage-like supramolecular dimer, in which the peripheral dioxane-type ether groups interlace by twelve noncovalent C-H⋅⋅⋅⋅⋅O bonds.

Constant oxidation of atrazine in Fe(III)/PDS system by enhancing Fe(III)/Fe(II) cycle with quinones: Reaction mechanism, degradation pathway and DFT calculation

Quinones are potential pollutants and redox active compounds widely distributed in environmental media. In this study, methyl-p-benzoquinone (MBQ) was introduced into Fe(III)/peroxydisulfate system (Fe(III)/PDS) to expedite the conversion of Fe(III) to Fe(II) and the degradation of atrazine (ATZ), ultimately establishing an environmentally friendly system of “treating pollution with pollution”. MBQ/Fe(III)/PDS system showed superior performance to traditional Fe(II)/PDS system in pH range of 2–7. Sulfate radical (SO4•−) and hydroxyl radical (•OH) were confirmed to exist in MBQ/Fe(III)/PDS system according to alcohol quenching experiments and ESR tests. Meanwhile, stable 80% of η[PMSO2] (i.e., the molar ratio of PMSO2 generation to PMSO consumption) was achieved and manifested that highly reactive substance Fe(IV) also participated in MBQ/Fe(III)/PDS system. The spontaneous transformation of MBQ and methyl-hydroquinone (MHQ) drove Fe(III)/Fe(II) cycle, during which MHQ induced Fe(III) reduction and Fe(II) regeneration. Transformation pathways of ATZ were proposed based on HPLC-MS detection and DFT calculation and ATZ degradation could be initiated by lateral chain oxidation and dechlorination-hydroxylation. The acute toxicity, bioaccumulation factor, developmental toxicity and mutagenicity of ATZ and its degradation intermediates were evaluated by Toxicity Estimation Software Tool, and the luminescent bacteria test was conducted to investigate the acute toxicity variation of the reaction solution. Cl− obviously inhibited ATZ degradation and three main by-products generation, while humic acid (HA) had little effect on them probably due to the established balance between inhibition (some components in HA competed to consume reactive species) and acceleration (quinone units in HA also facilitated Fe(III)/Fe(II) cycle).

Isomeric Triptycene Triquinones as Universal Cathode Materials for High Energy Alkali Metal Batteries

AbstractOrganic electrode materials have been extensively researched for alkali metal batteries such as Li, Na, and K batteries due to their unique redox mechanism independent of types of charge‐carrying ions and flexible intermolecular structures facilitating the insertion of bulky metal‐ions. This study presents an ortho‐isomer of triptycene tribenzoquinone (o‐TT) as a universal organic cathode material for alkali metal batteries. To elevate the redox potentials of previously reported triptycene tribenzoquinone (TT) without sacrificing its large specific capacity (∼386 mAh g−1), the structural isomers of benzoquinone units in the TT molecule were designed by changing their carbonyl group position from para‐ to ortho‐position. Due to multi‐electron redox reactions and the elevated redox potentials, o‐TT shows high energy densities of 945, 767, and 597 Wh kg−1 in Li, Na, and K cells, respectively. Finally, its cycle stability is significantly improved by fabricating composite electrodes with disordered mesoporous carbon (DOMC).

(Digital Presentation) Facile Synthesis of Pillar[6]Quinone and Investigation of Its Electrochemical Properties

Pillar[n]arene (n: number of units), macrocyclic para-arylene methylene molecules, have attracted attention owing to their symmetrical structures, host-guest properties, and original supramolecular assembly characteristics.1 Similarly, their quinone counterparts, pillar[n]quinone (P[Q]n), are also fascinating macrocycles containing electron-deficient quinone units, and therefore have potential application for novel host-guest chemistry and redox active materials. A hexagonal molecule, pillar[6]quinone (P[Q]6), is expected to form densely packed structures and a candidate for organic active material but the synthesis of P[Q]6 still remains a challenge.We previously demonstrated that the electrochemical oxidation (1.0 V vs. SCE) of 1,4-dihydroxypillar[6]arene (P[HQ]6) in methanol afforded micrometer scale hexagonal cylindrical depositions on electrode surfaces, which were composed of partially oxidized P[HQ]6-m[Q]m (composed of both hydroquinone and benzoquinone units) aggregating via quinhydrone formation.2 In this work, we successfully synthesized P[Q]6 for the first time by oxidation of its hydroquinone precursor P[HQ]6. Electrochemical oxidation (1.2 V vs. SCE) of P[HQ]6 in methanol gave the similar hexagonal cylindrical crystal of P[Q]6 evidenced by single crystal X-ray diffraction, NMR and HRMS analyses. In the crystallographic data, all quinone moieties seem to have intermolecular CH-O interaction between adjacent macrocycles, resulting in the formation of a hexagonal packing structure. In addition, we also found that scalable synthesis of P[Q]6 was possible by chemical oxidation of P[HQ]6 with phenyliodine(III)bis(trifluoroacetate) in 1,1,1,3,3,3-hexafluoro-2-propanol.To understand the electrochemical properties and electron-transfer behavior of P[Q]6, various voltametric studies were carried out. We revealed that three electrons are injected first, followed by stepwise three one-electron reductions due to the electrostatic repulsion in the latter electron-transfer process.Reference T. Ogoshi, T. Yamagishi, Y. Nakamoto, Chem. Rev., 116, 7937 (2016).C. Tsuneishi, Y. Koizumi, R. Sueto, H. Nishiyama, K. Yasuhara, T. Yamagishi, T. Ogoshi, Tomita and S. Inagi, Chem. Commun., 53, 7454 (2017).T. Hirohata, N. Shida, H. Uekusa, N. Yasuda, H. Nishihara, T. Ogoshi, I. Tomita, S. Inagi, Chem. Commun., 57, 6360 (2021). Figure 1

Boron-Functionalized Organic Framework as a High-Performance Metal-Free Catalyst for N2 Fixation.

Inspired by the recently synthesized covalent organic framework (COF) containing triquinoxalinylene and benzoquinone units (TQBQ) in the skeleton, we study the stability and properties of its two-dimensional analogue, TQBQCOF, and examine its potential for the synthesis of ammonia using first-principles calculations. We show that the TQBQCOF sheet is mechanically, dynamically, and thermally stable up to 1200 K. It is a semiconductor with a direct band gap of 2.70 eV. We further investigate the electrocatalytic reduction of N2to NH3on the Boron-functionalized TQBQCOF sheet (B/TQBQCOF). The rate-determining step of the catalytic pathways is found to be *N-N → *N-NH for the distal, alternating, and enzymatic catalytic mechanisms, with the corresponding overpotentials of 0.65, 0.65, and 0.07 V, respectively. The value of 0.07 V is the lowest required voltage among all of the N2 reduction catalysts reported so far, showing the potential of B/TQBQCOF as a metal-free catalyst to effectively reduce N2to NH3.