SlWRKY81 regulates Spd synthesis and Na+/K+ homeostasis through interaction with SlJAZ1 mediated JA pathway to improve tomato saline-alkali resistance.

Saline-alkali stress is an important abiotic stress factor affecting tomato (Solanum lycopersicum L.) plant growth. Although the involvement of the tomato SlWRKY gene family in responses to saline-alkali stress has been well established, the mechanism underlying resistance to saline-alkali stress remains unclear. In this study, we investigated the role of SlWRKY81 in conferring saline-alkali stress resistance by using overexpression and knockout tomato seedlings obtained via genetic modification. We demonstrated that SlWRKY81 improves the ability of tomato to withstand saline-alkali stress by enhancing antioxidant capacity, root activity, and proline content while reducing malondialdehyde levels. Saline-alkali stress induces an increase in jasmonic acid (JA) content in tomato seedlings, and the SlWRKY81 promoter responds to JA signaling, leading to an increase in SlWRKY81 expression. Furthermore, the interaction between SlJAZ1 and SlWRKY81 represses the expression of SlWRKY81. SlWRKY81 binds to W-box motifs in the promoter regions of SlSPDS2 and SlNHX4, thereby positively regulating their expression. This regulation results in increased spermidine (Spd) content and enhanced potassium (K+) absorption and sodium (Na+) efflux, which contribute to the resistance of tomato to saline-alkali stress. However, JA and SlJAZ1 exhibit antagonistic effects. Elevated JA content reduces the inhibitory effect of SlJAZ1 on SlWRKY81, leading to the release of additional SlWRKY81 protein and further augmenting the resistance of tomato to saline-alkali stress. In summary, the modulation of Spd synthesis and Na+/K+ homeostasis mediated by the interaction between SlWRKY81 and SlJAZ1 represents a novel pathway underlying tomato response to saline-alkali stress.

Metabolomics and transcriptomics analysis revealed the response mechanism of alfalfa to combined cold and saline-alkali stress.

Cold and saline-alkali stress are frequently encountered by plants, and they often occur simultaneously in saline-alkali soils at mid to high latitudes, constraining forage crop distribution and production. However, the mechanisms by which forage crops respond to the combination of cold and saline-alkali stress remain unknown. Alfalfa (Medicago sativa L.) is one of the most essential forage grasses in the world. In this study, we analyzed the complex response mechanisms of two alfalfa species (Zhaodong [ZD] and Blue Moon [BM]) to combined cold and saline-alkali stress using multi-omics. The results revealed that ZD had a greater ability to tolerate combined stress than BM. The tricarboxylic acid cycles of the two varieties responded positively to the combined stress, with ZD accumulating more sugars, amino acids, and jasmonic acid. The gene expression and flavonoid content of the flavonoid biosynthesis pathway were significantly different between the two varieties. Weighted gene co-expression network analysis and co-expression network analysis based on RNA-Seq data suggested that the MsMYB12 gene may respond to combined stress by regulating the flavonoid biosynthesis pathway. MsMYB12 can directly bind to the promoter of MsFLS13 and promote its expression. Moreover, MsFLS13 overexpression can enhance flavonol accumulation and antioxidant capacity, which can improve combined stress tolerance. These findings provide new insights into improving alfalfa resistance to combined cold and saline-alkali stress, showing that flavonoids are essential for plant resistance to combined stresses, and provide theoretical guidance for future breeding programs.

Origin and characterization of cyclodepsipeptides: Comprehensive structural approaches with focus on mass spectrometry analysis of alkali-cationized molecular species.

Cyclodepsipeptides (CDPs) represent a huge family of chemically and structurally diverse molecules with a wide ability for molecular interactions. CDPs are cyclic peptide-related natural products made up of both proteinogenic and nonproteinogenic amino acids linked by amide and ester bonds. The combined use of different analytical methods is required to accurately determine their integral structures including stereochemistry, thus allowing deeper insights into their often-intriguing bioactivities and their possible usefulness. Our goal is to present the various methods developed to accurately characterize CDPs. Presently, Marfey's method and NMR (nuclear magnetic resonance) are still considered the best for characterizing CDP configuration. Nevertheless, electrospray-high resolution tandem mass spectrometry (ESI-HRMS/MS) is of great value for efficiently resolving CDP's composition and sequences. For instance, recent data shows that the fragmentation of cationized CDPs (e.g., [M + Li]+ and [M + Na]+) leads to selective cleavage of ester bonds and specific cationized product ions (b series) useful to get unprecedented sequence information. Thus, after a brief presentation of their structure, biological functions, and biosynthesis, we also provide a historic overview of these various analytical approaches as well as their advantages and limitations with a special emphasis on the emergence of methods based on HRMS/MS through recent fundamental works and applications.

Small GTPase PvARFR2 interacts with Cytosolic ABA Receptor Kinase3 to enhance alkali tolerance in Switchgrass.

Soil alkalization has become a serious problem that limits plant growth through osmotic stress, ionic imbalance, and oxidative stress. Understanding how plants resist alkali stress has practical implications for alkaline-land utilization. In this study, we identified a small GTPase, PvARFR2 (ADP ribosylation factors related 2), that positively regulates alkali tolerance in switchgrass (Panicum virgatum) and uncovered its potential mode of action. Overexpressing PvARFR2 in switchgrass and Arabidopsis (Arabidopsis thaliana) conferred transformants tolerance to alkali stress, demonstrated by alleviated leaf wilting, less oxidative injury, and a lower Na+/K+ ratio under alkali conditions. Conversely, switchgrass PvARFR2-RNAi and its homolog mutant atgb1 in Arabidopsis displayed alkali sensitives. Transcriptome sequencing analysis showed that cytosolic ABA receptor kinase PvCARK3 transcript levels were higher in PvARFR2 overexpression lines compared to the controls and were strongly induced by alkali treatment in shoots and roots. Phenotyping analysis revealed that PvCARK3-OE×atgb1 lines were sensitive to alkali similar to the Arabidopsis atgb1 mutant, indicating that PvARFR2/AtGB1 functions in the same pathway as PvCARK3 under alkaline stress conditions. Application of ABA on PvARFR2-OE and PvCARK3-OE switchgrass transformants resulted in ABA sensitivity. Moreover, we determined that PvARFR2 physically interacts with PvCARK3 in vitro and in vivo. Our results indicate that a small GTPase, PvARFR2, positively responds to alkali stress by interacting with the cytosolic ABA receptor kinase PvCARK3, connecting the alkaline stress response to ABA signaling.

A Cost-Effective and Chemical-Recycling Approach for Facile Preparation of Regenerated Cellulose Materials.

Cellulose is difficult to melt or dissolve. The dissolution and regeneration process paves the way to convert cellulose into diverse forms but still suffers from high costs and environmental pollution. Here, we developed a method that uses aqueous alkali to efficiently dissolve cellulose at a temperature above 0 °C in minutes for fabricating regenerated cellulose. Cellulose was modified with minimal carboxymethyl groups to weaken the intermolecular interaction and improve its dissolution. The modified cellulose can be commercially obtained from carboxymethyl cellulose manufacturing with low cost and high quality. The use of only aqueous alkali reduces pollution and facilitates chemical recycling, and the moderate dissolving temperature reduces energy consumption. The regenerated cellulose materials display excellent mechanical properties and can be recycled or biodegraded after use. The method allows the use of diverse raw materials and modifications to broaden its applicability. The study develops a low-cost and eco-friendly method to fabricate regenerated cellulose.

Synergy Between Dynamic Behavior of Hydrogen Defects and Non-Radiative Recombination in Metal-Halide Perovskites.

In organic-inorganic hybrid perovskite solar cells (PSCs), hydrogen defects introduce deep-level trap states, significantly influencing non-radiative recombination processes. Those defects are primarily observed in MA-PSCs rather than FA-PSCs. As a result, MA-PSCs demonstrated a lower efficiency of 23.6% compared to 26.1% of FA-PSCs. In this work, both hydrogen vacancy (VH -) and hydrogen interstitial (Hi -) defects in MAPbI3 bulk and on surfaces, respectively are investigated. i) Bulk VH - defects have dramatic impact on non-radiative recombination, with lifetime varying from 67 to 8 ns, depending on whether deprotonated MA0 are ion-bonded or not. ii) Surface H-defects exhibited an inherent self-healing mechanism through a chemical bond between MA0 and Pb2+, indicating a self-passivation effect. iii) Both VH - and Hi - defects can be mitigated by alkali cation passivation; while large cations are preferable for VH - passivation, given strong binding energy of cation/perovskite, as well as, weak band edge non-adiabatic couplings; and small cations are suited for Hi - passivation, considering the steric hindrance effect. The dual passivation strategy addressed diverse experimental outcomes, particularly in enhancing performance associated with cation selections. The dynamic connection between hydrogen defects and non-radiative recombination is elucidated, providing insights into hydrogen defect passivation essential for high-performance PSCs fabrication.

Green and Low-Cost Alkali-Polyphenol Synergetic Self-Catalysis System Access to Fast Gelation of Self-Healable and Self-Adhesive Conductive Hydrogels for Self-Powered Triboelectric Nanogenerators.

Biomass-based hydrogels have attracted great attention in flexible and sustainable self-powered power sources but struggled to fabricate in a green, high-efficiency, and low-cost manner. Herein, a novel and facile alkali-polyphenol synergetic self-catalysis system is originally employed for the fast gelation of self-healable and self-adhesive lignin-based conductive hydrogels, which can be regarded as hydrogel electrodes of flexible triboelectric nanogenerators (TENGs). This synergy self-catalytic system comprises aqueous alkali and polyphenol-containing lignin, in which alkali-activated ammonium persulfate (APS) significantly accelerates the generation of radicals and initiates the polymerization of monomers, while polyphenol acts as a stabilizer to avoid bursting polymerization from inherent radical scavenging ability. Furthermore, multiple hydrogen bonds between lignin biopolymers and polyacrylamide (PAM) chains impart lignin-based hydrogels with exceptional adhesiveness and self-healing properties. Intriguingly, the alkaline conditions not only contribute to the solubility of lignin but also impart superior ionic conductivity of lignin-based hydrogel that is applicable to flexible TENG in self-powered energy-saving stair light strips, which holds great promise for industrial applications of soft electronics.

Ultra-Thin Hydrogen-Organic-Framework (HOF) Nanosheets for Ultra-Stable Alkali Ions Battery Storage.

Organic frameworks-based batteries with excellent physicochemical stability and long-term high capacity will definitely reduce the cost, carbon emissions, and metal consumption and contamination. Here, an ultra-stable and ultra-thin perylene-dicyandiamide-based hydrogen organic framework (HOF) nanosheet (P-DCD) of ≈3.5 nm in thickness is developed. When applied in the cathode, the P-DCD exhibits exceptional long-term capacity retention for alkali-ion batteries (AIBs). Strikingly, for lithium-ion batteries (LIBs), at current of 2 A g-1, the large reversible capacity of 108 mA h g-1 shows no attenuation within 5 000 cycles. For sodium-ion batteries (SIBs), the related capacity retains 91.7% within 10 000 cycles compared to the initial state, significantly much more stable than conventional organic materials reported previously. Mechanism studies through ex situ and in situ experiments and theoretical density functional theory (DFT) calculations reveal that the impressive long-term performance retention originates from the large electron delocalization, fast ion diffusion, and physicochemical stability within the ultra-thin 2D P-DCD, featuring π-π and hydrogen bonding stacking, nitrogen-rich units, and low impedance. The advantageous features demonstrate that rationally designed stable and effective organic frameworks pave the way to utilizing complete organic materials for developing next-generation low-cost and highly stable energy storage batteries.

A Multi-Interface Structure of Graphdiyne/Cobalt Oxides for Chlorine Production.

A challenge facing the chlor-alkali process is the lack of electrocatalyst with high activity and selectivity for the efficient industrial production of chlorine. Herein the authors report a new electrocatalyst that can generate multi-interface structure by in situ growth of graphdiyne on the surface of cobalt oxides (GDY/Co3O4), which shows great potential in highly selective and efficient chlorine production. This result is due to the strong electron transfer and high density charge transport between GDY and Co3O4 and the interconversion of the mixed valence states of the Co atoms itself. These intrinsic characteristics efficiently enhance the conductivity of the catalyst, facilitate the reaction kinetics, and improve the overall catalytic selectivity and activity. Besides, the protective effect of the formed GDY layer is remarkable endowing the catalyst with excellent stability. The catalyst can selectively produce chlorine in low-concentration of NaCl aqueous solution at room temperature and pressure with the highest Faraday efficiency of 80.67% and an active chlorine yield rate of 184.40 mg h-1 cm-2, as well as superior long-term stability.

Multifunctional Super-Hydrophilic MXene/Biomass Composite Aerogel Evaporator for Efficient Solar-Driven Desalination and Wastewater Treatment.

Solar-driven interfacial evaporation is recognized as a sustainable and effective strategy for desalination to mitigate the freshwater scarcity issue. Nevertheless, the challenges of oil contamination, salt accumulation, and poor long-term stability of the solar desalination process limit its applications. Herein, a 3D biomass-based multifunctional solar aerogel evaporator is developed for water production with fabricated chitosan/lignin (CSL) aerogel as the skeleton, encapsulated with carbonized lignin (CL) particles and Ti3C2TiX (MXene) nanosheets as light-absorbing materials. Benefitting from its super-hydrophilic wettability, interconnected macropore structure, and high broadband light absorption (ca. 95.50%), the prepared CSL-C@MXene-20 mg evaporator exhibited a high and stable water evaporation flux of 2.351 kg m-2 h-1 with an energy conversion efficiency of 88.22% under 1 Sun (1 kW m-2) illumination. The CSL-C@MXene-20 mg evaporator performed excellent salt tolerance and long-term solar vapor generation in a 3.5 wt.% NaCl solution. Also, its super-hydrophilicity and oleophobicity resulted in superior salt resistance and anti-fouling performance in high salinity brine (20 wt.% NaCl) and oily wastewater. This work offers new insight into the manufacture of porous and eco-friendly biomass-based photothermal aerogels for advanced solar-powered seawater desalination and wastewater purification.

Low-Temperature and Fast-Charge Sodium Metal Batteries.

Low-temperature operation of sodium metal batteries (SMBs) at the high rate faces challenges of unstable solid electrolyte interphase (SEI), Na dendrite growth, and sluggish Na+ transfer kinetics, causing a largely capacity curtailment. Herein, low-temperature and fast-charge SMBs are successfully constructed by synergetic design of the electrolyte and electrode. The optimized weak-solvation dual-salt electrolyte enables high Na plating/stripping reversibility and the formation of NaF-rich SEI layer to stabilize sodium metal. Moreover, an integrated copper sulfide electrode is in situ fabricated by directly chemical sulfuration of copper current collector with micro-sized sulfur particles, which significantly improves the electronic conductivity and Na+ diffusion, knocking down the kinetic barriers. Consequently, this SMB achieves the reversible capacity of 202.8 mAh g-1 at -20 °C and 1 C (1 C = 558 mA g-1). Even at -40 °C, a high capacity of 230.0 mAh g-1 can still be delivered at 0.2 C. This study is encouraging for further exploration of cryogenic alkali metal batteries, and enriches the electrode material for low-temperature energy storage.

Rb-Doped Perovskite Oxides: Surface Enrichment and Structural Reconstruction During the Oxygen Evolution Reaction.

Alkali-metal doped perovskite oxides have emerged as promising materials due to their unique properties and broad applications in various fields, including photovoltaics and catalysis. Understanding the complex interplay between alkali metal doping, structural modifications, and their impact on performance remains a crucial challenge. In this study, this challenge is addressed by investigating the synthesis and properties of Rb-doped perovskite oxides. These results reveal that the doping of Rb into perovskite oxides function as a structural modifier in the as-synthesized samples and during the oxygen evolution reaction (OER) as well. Electron microscopy and first-principles calculations confirm the enrichment of Rb on the surface of the as-synthesized sample. Further investigations into the electrocatalytic reaction revealed that the Rb-doped perovskite underwent drastic restructuring with Rb leaching and formation of strontium oxide.

Recent Advances in Pristine Iron Triad Metal-Organic Framework Cathodes for Alkali Metal-Ion Batteries.

Pristine iron triad metal-organic frameworks (MOFs), i.e., Fe-MOFs, Co-MOFs, Ni-MOFs, and heterometallic iron triad MOFs, are utilized as versatile and promising cathodes for alkali metal-ion batteries, owing to their distinctive structure characteristics, including modifiable and designable composition, multi-electron redox-active sites, exceptional porosity, and stable construction facilitating rapid ion diffusion. Notably, pristine iron triad MOFs cathodes have recently achieved significant milestones in electrochemical energy storage due to their exceptional electrochemical properties. Here, the recent advances in pristine iron triad MOFs cathodes for alkali metal-ion batteries are summarized. The redox reaction mechanisms and essential strategies to boost the electrochemical behaviors in associated electrochemical energy storage devices are also explored. Furthermore, insights into the future prospects related to pristine iron triad MOFs cathodes for lithium-ion, sodium-ion, and potassium-ion batteries are also delivered.

Electrochemical Investigations of Sulfur-Decorated Organic Materials as Cathodes for Alkali Batteries.

Alkali metal-sulfur batteries (particularly, lithium/sodium- sulfur (Li/Na-S)) have attracted much attention because of their high energy density, the natural abundance of sulfur, and environmental friendliness. However, Li/Na-S batteries still face big challenges, such as limited cycle life, poor conductivity, large volume changes, and the "shuttle effect" caused by the high solubility of Li/Na-polysulfides. Herein, novel organosulfur-containing materials, i.e., bis(4-hydroxy-2,2,6,6-tetramethylpiperidin-1-yl)disulfide (BiTEMPS-OH) and 2,4-thiophene/arene copolymer (TAC) are proposed as cathode materials for Li and Na batteries. BiTEMPS-OH shows an initial discharge/charge capacity of 353/192 mAh g-1 and a capacity of 62 mAh g-1 after 200 cycles at 100 mA g-1 in ether-based Li-ion electrolyte. Meanwhile, TAC has an initial discharge/charge capacity of 270/248 mAh g-1 and better cycling performance (106 mAh g-1 after 200 cycles) than BiTEMPS-OH in the same electrolyte. However, the rate capability of TAC is limited by the slow diffusion of Li-ions. Both materials show inferior electrochemical performances in Na battery cells compared to the Li analogs. X-ray powder diffraction reveals that BiTEMPS-OH loses its crystalline structure permanently upon cycling in Li battery cells. X-ray photoelectron spectroscopy demonstrates the cleavage and partially reversible formation of S-S bonds in BiTEMPS-OH and the formation/decomposition of thick solid electrolyte interphase on the electrode surface of TAC.

An Active Strategy to Reduce Residual Alkali for High-Performance Layered Oxide Cathode Materials of Sodium-Ion Batteries.

Residual alkali is one of the biggest challenges for the commercialization of sodium-based layered transition metal oxide cathode materials since it can even inevitably appear during the production process. Herein, taking O3-type Na0.9Ni0.25Mn0.4Fe0.2Mg0.1Ti0.05O2 as an example, an active strategy is proposed to reduce residual alkali by slowing the cooling rate, which can be achieved in one-step preparation method. It is suggested that slow cooling can significantly enhance the internal uniformity of the material, facilitating the reintegration of Na+ into the bulk material during the calcination cooling phase, therefore substantially reducing residual alkali. The strategy can remarkably suppress the slurry gelation and gas evolution and enhance the structural stability. Compared to naturally cooled cathode materials, the capacity retention of the slowly cooled electrode material increases from 76.2% to 85.7% after 300 cycles at 1 C. This work offers a versatile approach to the development of advanced cathode materials toward practical applications.

Rational Design of Naphthol Groups Functionalized Bipolar Polymer Cathodes for High Performance Alkali-Ion Batteries.

Redox-active organic compounds gather significant attention for their potential application as electrodes in alkali ion batteries, owing to the structural versatility, environmental friendliness, and cost-effectiveness. However, their practical applications of such compounds are impeded by insufficient active sites with limited capacity, dissolution in electrolytes, and sluggish kinetics. To address these issues, a naphthol group-containing triarylamine polymer, namely poly[6,6'-(phenylazanediyl)bis(naphthol)] (poly(DNap-OH)) is rationally designed and synthesized, via oxidative coupling polymerization. It is capable of endowing favorable steric structures that facilitate fast ion diffusion, excellent chemical stability in organic electrolytes, and additional redox-active sites that enable a bipolar redox reaction. By exploiting these advantages, poly(DNap-OH) cathodes demonstrate remarkable cycling stability in both lithium-ion batteries (LIBs) and potassium-ion batteries (PIBs), showcasing enhanced specific capacity and redox reaction kinetics in comparison to the conventional poly(4-methyltriphenylamine) cathodes. Overall, this work offers insights into molecular design strategies for the development of high-performance organic cathodes in alkali-ion batteries.

Revealing Roles of High-Electronegativity Fluorine Atoms in Boosting Redox Potential of Layered Sodium Cathodes.

The development of high-energy-density cathode materials is regarded as the ultimate goal of alkali metal-ion batteries energy storage. However, the strategy of regulating specific capacity is limited by the theoretical capacity, and meanwhile focusing on improving capacity will lead to structural destructions. Herein, a novel perspective is proposed that tuning the electronic band structure by introducing highly electronegative fluoride atoms in NaxTMO2-yFy (0 < x < 1, 0 < y < 2) model compounds to improve redox potential for developing high-energy-density layered oxides. Highly electronegative fluoride atoms is introduced into P2-type Na0.67Fe0.5Mn0.5O2 (NFM), and the thus fluoride NFM (F-NFM) cathode achieved high redox potential (3.0 V) and high energy density (446 Wh kg-1). Proved by structural characterizations, fluorine atoms are successfully incorporated into oxygen sites in NFM lattice. Ultraviolet photoelectron spectroscopy is applied to quantitatively analyze the improved redox potential of F-NFM, which is achieved by the decreased valence band energy in electronic band structure due to the strongly electrophilic fluoride ions. Moreover, fluoride atoms can stabilize the local environment of NFM and improve its redox potential. The work provides a perspective to improve redox potential by tuning the electronic band structure in layered oxides and developing high-energy-density alkali metal-ion batteries.

Redesigning a S-nitrosylated pyruvate-dependent GABA transaminase 1 to generate high-malate and saline-alkali-tolerant tomato.

Although saline-alkali stress can improve tomato quality, the detailed molecular processes that balance stress tolerance and quality are not well-understood. Our research links nitric oxide (NO) and γ-aminobutyric acid (GABA) with the control of root malate exudation and fruit malate storage, mediated by aluminium-activated malate transporter 9/14 (SlALMT9/14). By modifying a specific S-nitrosylated site on pyruvate-dependent GABA transaminase 1 (SlGABA-TP1), we have found a way to enhance both plant's saline-alkali tolerance and fruit quality. Under saline-alkali stress, NO levels vary in tomato roots and fruits. High NO in roots leads to S-nitrosylation of SlGABA-TP1/2/3 at Cys316/258/316, reducing their activity and increasing GABA. This GABA then reduces malate exudation from roots and affects saline-alkali tolerance by interacting with SlALMT14. In fruits, a moderate NO level boosts SlGABA-TP1 expression and GABA breakdown, easing GABA's block on SlALMT9 and increasing malate storage. Mutants of SlGABA-TP1C316S that do not undergo S-nitrosylation maintain high activity, supporting malate movement in both roots and fruits under stress. This study suggests targeting SlGABA-TP1Cys316 in tomato breeding could significantly improve plant's saline-alkali tolerance and fruit quality, offering a promising strategy for agricultural development.

Prediction of Covalent Metal-Metal Bonding in Cp-M-M'-Nacnac Complexes of Group 2 and 12 Metals (Be, Mg, Ca, Zn, Cd, Hg).

Bimetallic CpMM'Nacnac molecules with group 2 and 12 metals (M=Be, Mg, Ca, Zn, Cd, Hg) that contain novel metal-metal bonding have been investigated in a theoretical study of their molecular and electronic structure, thermodynamic stability, and metal-metal bonding. In all cases the metal-metal bonds are characterized as electron-sharing covalent single bonds from natural bond orbital (NBO) and energy-decomposition analysis with natural orbitals of chemical valence (EDA-NOCV) analysis. The sum of [MM'] charges is relatively constant, with all complexes exhibiting a [MM']2+ core. Quantum theory of atoms in molecules (QTAIM) analysis indicates the presence of non-nuclear attractors (NNA) in the metal-metal bonds of the BeBe, MgMg, and CaCa complexes. There is substantial electron density (0.75-1.33 e) associated with the NNAs, which indicates that these metal-metal bonds, while classified as covalent electron-sharing bonds, retain significant metallic character that can be associated with reducing reactivity of the complex. The predicted stability of these complexes, combined with their novel covalent metal-metal bonding and potential as reducing agents, make them appealing targets for the synthesis of new metal-metal bonds.

Bending a Cumulene with Electrons: Stepwise Chemical Reduction and Structural Study of a Tetraaryl[4]Cumulene.

Chemical reduction of a [4]cumulene with cesium metal was explored, and the structural changes stemming from electron acquisition are detailed using X-ray crystallography. It is found that the [4]cumulene undergoes dramatic geometric changes upon stepwise reduction, including bending of the cumulenic core and twisting of the endgroups from orthogonal to planar. The structural deformation is consistent with early theoretical reports that suggest that the twisting should occur upon reduction of both even and odd [n]cumulenes. The current results, on the other hand, are inconsistent with a previous experimental study of a [3]cumulene in which the predicted twisting is not observed upon reduction. DFT calculations reveal that the barrier to deformation is an order of magnitude lower in a [3]cumulene than a [4]cumulene, allowing the barrier to be overcome in the solid-state.