Search

Trap‐assisted non‐radiative recombination losses and moisture‐induced degradation significantly impede the development of highly efficient and stable inverted (p–i–n) perovskite solar cells (PSCs), which require high‐quality perovskite bulk. In this research, we mitigate these challenges by integrating thermally stable perovskite layers with Lewis base covalent organic frameworks (COFs). The ordered pore structure and surface binding groups of COFs facilitate cyclic, multi‐site chelation with undercoordinated lead ions, enhancing the perovskite quality across both its bulk and grain boundaries. This process not only reduces defects but also promotes improved energy alignment through n‐type doping at the surface. The inclusion of COF dopants in p–i–n devices achieves power conversion efficiencies (PCEs) of 25.64 % (certified 24.94 %) for a 0.0748‐cm2 device and 23.49 % for a 1‐cm2 device. Remarkably, these devices retain 81 % of their initial PCE after 978 hours of accelerated aging at 85°C, demonstrating remarkable durability. Additionally, COF‐doped devices demonstrate excellent stability under illumination and in moist conditions, even without encapsulation. [ABSTRACT FROM AUTHOR]

Gallylene supported by a bis(oxazolinyl)(phenyl)methanide (Boxm) ligand was synthesized and structurally characterized. The reaction of this gallylene with triphenylphosphine sulfide/selenide yielded dimeric gallium sulfide and selenide. These compounds could be converted to monomeric terminal sulfide and selenide by coordination of an external Lewis base such as an N‐heterocyclic carbene (NHC or IMe4) and 4‐dimethylaminopyridiene (DMAP). These doubly‐base‐stabilized gallium sulfide/selenide reacted with phenyl isocyanate to give the corresponding cycloadducts by releasing the Lewis base, indicating the formation of a single‐base‐stabilized gallium sulfide/selenide intermediate. [ABSTRACT FROM AUTHOR]

High safety and stability in batteries are crucial factors for the large‐scale application of lithium‐ion technology. In this work, flame‐retardant aluminum diethylphosphonite (ADP) is coated by urea‐formaldehyde (UF) shell to conquer the side reactions caused by ADP during cycling process. And then the core@shell structured ADP@UF is combined with poly(ethylene oxide) (PEO), high thermal stability can be realized. When exposed to high temperatures, ADP@UF generates N⋅ and P⋅ radicals to eliminate the combustion the H⋅ and OH⋅ radical, to inhibit fire. By controlling the percentage of flame retardant added, PEO‐ADP@UF has totally achieved the effect of inflaming retarding, realizing stable electrochemical properties at the same time. The −NH2 in UF forms hydrogen bonds with PEO, and acts as a Lewis base to promote the dissociation of lithium salts to increase the lithium‐ion mobility number. Compared to PEO, battery with PEO‐ADP@UF has outstanding cycling performance (103 mAh g−1 at 1 C, 2.5–4.2 V) and long service life (800 cycles). [ABSTRACT FROM AUTHOR]

Lewis base additives typically undergo interactions with SnI2 to achieve effective defect passivation in lead-free perovskite films. In this work, the thiophene ring in 2-thiophenethylammonium chloride (TEACl) has coordination interactions with Sn2+ and the -NH3+ therein forms hydrogen bonds with I-. This facilitates the deposition of homogeneous and dense films with fewer defects during crystallization process. Otherwise, 2-pyridinethylammonium chloride (AEPCl) gives poorly perovskite films with high defect density because of the overly strong interaction with SnI2. As a result, the average photoluminescence life time of TEACl-passivated perovskite film was substantially increased to 22.04 ns, compared with the control film (5.15 ns) and the AEPCl-passivated film (3.55 ns). Ultimately, the target solar cell with TEACl passivation presented a power conversion efficiency of 13.24% and excellent shelf-stand stability with a 90% retaining of initial efficiency after 2000 h of aging in N2 atmosphere. This work sheds new light on the structural tailoring of Lewis base passivators for efficient defect passivation in lead-free tin halide perovskites.

We report the preparation of a new organic σ‐donor with a C6H4‐linker between an N‐heterocyclic carbene (NHC) and an exocyclic methylidene group, which we term N‐heterocyclic quinodimethane (NHQ). The aromatization of the C6H4‐linker provides a decisive driving force for the reaction of the NHQ with an electrophile and renders the NHQ significantly more basic than analogous NHCs or N‐heterocyclic olefins (NHOs), as shown by DFT computations and competition experiments. In solution, the NHQ undergoes an unprecedented dehydrogenative head‐to‐head dimerization by C−C coupling of the methylidene groups. DFT computations indicate that this reaction proceeds via an open‐shell singlet pathway revealing the diradical character of the NHQ. The product of this dimerization can be described as conjugated N‐heterocyclic bis‐quinodimethane, which according to cyclic voltammetry is a strong organic reducing agent (E1/2=−1.71 V vs. Fc/Fc+) and exhibits a remarkable small singlet–triplet gap of ΔES→T=4.4 kcal mol−1. [ABSTRACT FROM AUTHOR]

Spirooxindoles are privileged scaffolds in diverse bioactive natural products and pharmaceuticals, significant achievements for the construction of these molecules have thus been made in the past years. Among them, organocatalysis, in particular, nucleophilic Lewis base catalysis, has recently emerged as an efficient and reliable method for the preparation of diverse and valuable functionalized spirooxindoles. According to different kinds of nucleophilic catalysts, we summarize and classify three catalytic strategies; these are tertiary amine‐catalyzed cycloadditions, NHC‐catalyzed cycloadditions, and tertiary phosphine‐catalyzed cycloadditions, respectively. Through these methods, potential bioactive spirooxindole skeletons owning various functional groups can be produced to enrich the small organic molecule library. In this review, we describe a comprehensive and updated advances of nucleophilic Lewis base catalytic cycloaddition reactions for the construction of spirooxindoles. Meanwhile, the related mechanism and the application of these annulation strategies in natural product total synthesis will be highlighted in detail. [ABSTRACT FROM AUTHOR]

The dinuclear bis(N‐heterocyclic carbene) borane adduct 2 rapidly reacts with tritylium salts at room temperature but the outcome is strongly impacted by the respective counter‐ion. Using tritylium tetrakis(perfluoro‐tert‐butoxy)aluminate affords – depending on the solvent – either the bis(boronium) ion 4 or the hydride‐bridged dication 5. In case of tritylium hexafluorophosphate, however, H/F exchange occurs between boron and phosphorus yielding the dinuclear BF3 adduct 3 along with phosphorus dihydride trifluoride. H/F exchange also takes place when using the mononuclear N‐heterocyclic carbene BH3 adduct 6 and hence provides a facile route to PH2F3, which is usually synthesized in more complex reaction sequences regularly involving toxic hydrogen fluoride. DFT calculations shed light on the H/F exchange between the borenium ion and the [PF6]− counter‐ion and the computed mechanism features only small barriers in line with the experimental observations. [ABSTRACT FROM AUTHOR]

We have quantum chemically studied the influence of ring strain on the competition between the two mechanistically different SN2 and E2 pathways using a series of archetypal ethers as substrate in combination with a diverse set of Lewis bases (F−, Cl−, Br−, HO−, H3CO−, HS−, H3CS−), using relativistic density functional theory at ZORA‐OLYP/QZ4P. The ring strain in the substrate is systematically increased on going from a model acyclic ether to a 6‐ to 5‐ to 4‐ to 3‐membered ether ring. We have found that the activation energy of the SN2 pathway sharply decreases when the ring strain of the system is increased, thus on going from large to small cyclic ethers, the SN2 reactivity increases. In contrast, the activation energy of the E2 pathway generally rises along this same series, that is, from large to small cyclic ethers. The opposing reactivity trends induce a mechanistic switch in the preferred reaction pathway for strong Lewis bases from E2, for large cyclic substrates, to SN2, for small cyclic substrates. Weak Lewis bases are unable to overcome the higher intrinsic distortivity of the E2 pathway and, therefore, always favor the less distortive SN2 reaction. [ABSTRACT FROM AUTHOR]

[34] The reaction with enantioenriched -methylbenzylboronic acid pinacol ester resulted in a 56:44 diastereomeric mixture of alcohol products B 48 b , the same diastereomeric mixture as was observed using racemic alkylboronic ester. [3][5][6] This short review details our laboratory's examination of reactions using benzylboronic acid pinacol ester and secondary and tertiary benzylboronic esters as nucleophiles. Keywords: boron; benzylation; Lewis base; copper; boronate EN boron benzylation Lewis base copper boronate 2639 2647 9 08/17/23 20230901 NES 230901 Graph 1 Introduction Organoboranes have found great utility in organic synthesis. Specifically, substrates containing esters and amides to the ketone were found to be compatible under these reaction conditions with no reaction being observed at the ester or amide carbonyl carbon ( B 25 b and B 26 b ). [Extracted from the article]

The encounter complex, i.e. , the pre-organized assembly consisting of a Lewis acid and a Lewis base, is a fundamental concept in frustrated Lewis pair (FLP) chemistry. However, this donor–acceptor complex is challenging to study due to its transient nature. Here, we present a combined theoretical and experimental investigation on the potential isolation of an encounter complex enabled by enhancement of London dispersion forces between a sterically encumbered Lewis acid and base pair. Guided by computational analyses, the FLP originating from the bulky triarylamine N(3,5- t Bu2 C6 H3)3 and the novel triarylborane B(3,5- t Bu2 C6 H3)3 was investigated, leading to the isolation of a 1:1 co-crystal of both FLP components. [ABSTRACT FROM AUTHOR]

The novel organic salt 7-((5-bromo-1H-indol-3-yl)(4-methoxyphenyl)methyl)1,3,5-triaza-7-phosphaadamantan-7-ium tetrafluoroborate was synthesized from a Lewis acid (LA) and Lewis-base (LB) reaction between 1,3,5-triaza-7-phosphaadmantane (LB) and 5-bromo-3-(4-methoxybenzylidene)-3-H-indol-1-ium tetrafluoroborate (LA). The obtained Lewis acid base adduct, being the title compound, was analyzed and validated by 1H, 13C, 31P, and 19F 1D-NMR-spectroscopy, ESI mass spectrometry, CHN-elemental analysis, and a single crystal X-ray diffraction investigation. [ABSTRACT FROM AUTHOR]

The inferior phase stability and unsatisfactory crystal quality of inorganic lead halide perovskites have severely impeded the development of inorganic perovskite solar cells. Herein, a bifunctional Lewis base additive, phenylthiourea (PTU), is incorporated into the CsPbIBr2 precursor to simultaneously enhance the quality and ameliorate the stability of the CsPbIBr2 perovskite film. The CS group of PTU strongly coordinates with PbBr2 to form the intermediate phase in the perovskite precursor, which effectively tunes the crystallization process of CsPbIBr2 and enables the formation of high‐quality CsPbIBr2 perovskite film with high crystallinity, large crystal grains, and indistinct grain boundaries. Meanwhile, the introduction of PTU additive leads to the sulfur insertion into the interstices of CsPbIBr2 perovskite lattice, which can stabilize the perovskite phase structure and passivate the undercoordinated Pb2+ defects. With these benefits, the assembled carbon‐based perovskite solar cell based on PTU‐CsPbIBr2 perovskite film delivers a high power conversion efficiency of 10.09%. In addition, the unencapsulated device maintains over 80% of its initial efficiency after 800 h of storage under ambient air. These results demonstrate an effective strategy to improve the performance and stability of inorganic perovskite solar cells. [ABSTRACT FROM AUTHOR]

Hydrosilylation reactions are commonly used for the reduction of carbonyl bonds in fine chemistry, catalyzed by transition metal complexes. The current challenge is to expand the scope of metal‐free alternative catalysts, including in particular organocatalysts. This work describes the organocatalyzed hydrosilylation of benzaldehyde with a phosphine, introduced at 10 mol%, and phenylsilane at room temperature. The activation of phenylsilane was highly dependent on the physical properties of the solvent such as the polarity, and the highest conversions were obtained in acetonitrile and propylene carbonate with yields of 46 % and 97 %, respectively. The best results of the screening over 13 phosphines and phosphites were obtained with linear trialkylphoshines (PMe3, PnBu3, POct3), indicating the importance of their nucleophilicity, with yields of 88 %, 46 % and 56 %, respectively. With the help of heteronuclear 1H−29Si NMR spectroscopy, the products of the hydrosilylation (PhSiH3‐n(OBn)n) were identified, allowing a monitoring of the concentration in the different species, and thereby of their reactivity. The reaction displayed an induction period of ca. 60 min, followed by the sequential hydrosilylations presenting various reaction rates. In agreement with the formation of partial charges in the intermediate state, we propose a mechanism based on a hypervalent silicon center via the Lewis base activation of the silicon Lewis acid. [ABSTRACT FROM AUTHOR]

Electron transport materials (ETMs) play a vital role in electron extraction and transport at the perovskite/ETM interface of inverted perovskite solar cells (PSCs) and are useful in power conversion efficiency (PCE), which is limited by interface carrier recombination. However, strategies for passivating undercoordinated Pb2+ at the perovskite/ETM interface employing ETMs remain a challenge. In this work, a variety of heteroatoms were used to strengthen the Lewis base property of new ETMs (asymmetrical perylene-diimide), aimed at deactivating non-bonded Pb2+ at the perovskite surface through Lewis acid-base coordination. Quantum chemical analysis revealed that novel ETMs have matched the energy level of perovskite, which enables electron extraction at the perovskite/ETM interface. The results also suggest that the large electron mobility (0.57~5.94 cm2 V−1 s−1) of designed ETMs shows excellent electron transporting ability. More importantly, reinforced interaction between new ETMs and Pb2+ was found, which is facilitating to passivation of the defects induced by unsaturated Pb2+ at the perovskite/ETM interface. Furthermore, it is found that MA (CH3NH3+), Pb, and IPb (iodine substituted on the Pb site) defects at the perovskite/ETM interface could be effectively deactivated by the new ETMs. This study provides a useful strategy to design ETMs for improving the interface property in PSCs. [ABSTRACT FROM AUTHOR]

The changes in absorption and emission of fluorescent materials with the introduction of Lewis acids have been frequently observed due to either physical or chemical interactions. In this mini-review, we elaborate how Lewis acids adjust the optical properties and the bandgap of luminescent materials by simple coordination reactions. It is common that fluorescent materials containing Lewis basic nitrogen heterocycles are more likely to provide the feasible band gap modulation. The essence of such phenomenon originates from Lewis acid–base coordination and adducts, which highly depends on the electron-accepting property of the Lewis acids. This intermolecular mechanism, considered as post-synthesis of new luminescent compounds offers promising applications in sensing and electroluminescence by manipulating the frontier molecular orbital energy levels of organic conjugated materials, simply based on Lewis acid–base chemistry.

The novel organic salt 7-((5-bromo-1H-indol-3-yl)(4-methoxyphenyl)methyl)1,3,5-triaza-7-phosphaadamantan-7-ium tetrafluoroborate was synthesized from a Lewis acid (LA) and Lewis-base (LB) reaction between 1,3,5-triaza-7-phosphaadmantane (LB) and 5-bromo-3-(4-methoxybenzylidene)-3-H-indol-1-ium tetrafluoroborate (LA). The obtained Lewis acid base adduct, being the title compound, was analyzed and validated by 1H, 13C, 31P, and 19F 1D-NMR-spectroscopy, ESI mass spectrometry, CHN-elemental analysis, and a single crystal X-ray diffraction investigation.

The possible existence of nonagermanide deltahedral Zintl ion (Ge94−) as a nine-folded Lewis base is investigated from first principles calculations. It is observed that all nine centres, Ge94−, can make an adduct with Lewis acid. The presence of lone pairs is confirmed from the 1c–2e AdNDP calculation. It is further noticed that the bulky group functionalized organo-Zintl cluster, [Ge9(tBu)3]− , can potentially act as a Lewis base and can make an intermolecular frustrated Lewis pair (FLP) with a well-known Lewis acid Tris[2,4,6-tris(trifluoromethyl)phenyl] borane, [B{C6H2(CF3)3}3]. [ABSTRACT FROM AUTHOR]

Phosphanylgallane with hydrogen and halogen substituents (RXGa−PHR, R=organic substituent, X=halogen/hydrogen) are regarded as putative suitable precursors for accessing Ga=P doubly bonded species. Herein, we report on the synthesis, structure, and bonding analysis of a series of Lewis base‐ and Lewis acid/base‐stabilized phosphanylgallane bearing P−H and Ga−Cl/H substitution. To avoid oligomerization, the treatment of IDip.GaCl3 and (IDip)GaH2Cl (IDip=1,3‐bis(2,6‐diisopropylphenyl) imidazole‐2‐ylidene) with LiPHR or LiPHR(BH3) (R=Ph, Tip, Mes, NiPr2, NCy2) affords the corresponding Lewis base and Lewis acid/base coordinated H,Cl‐functionalized monomeric phosphanylgallane, respectively. The structure of these derivatives were determined by spectroscopic and X‐ray crystallographic analyses. The observed Ga−P bond lengths are comparable to those previously reported phosphanylgallane analogues. The nature of the CIDip‐Ga coordination bond was assessed with Energy Decomposition Analysis, suggesting a relatively stable adduct. Reactions of the phosphanylgallane with Brønsted bases were investigated. [ABSTRACT FROM AUTHOR]

We report herein a new method for the synthesis of densely functionalized chiral allyl SCF3, SCF2R, SCN and SAr species with a separate CF3 functionality. The synthetic approach is based on selenium‐catalyzed sulfenofunctionalization of chiral α‐CF3 allylboronic acids. The reactions proceeded with remarkably high stereo‐, diastereo‐ and site‐selectivity, based on the formation of a stable thiiranium ion followed by rapid deborylative ring opening. [ABSTRACT FROM AUTHOR]

The oxidative electrochemistry of cymantrene, CpMn(CO)3 (1; Cp = [η5-C5H5]–), was examined in ionic liquids (ILs) composed of anions of varying Lewis base properties. It was observed that the cyclic voltammetric responses strongly depended on the nucleophilic properties of the IL anion. Still, all observations are consistent with the initial formation of 1+ followed by an attack from the IL anion. In bis(trifluoromethylsulfonyl)amide [NTf2]-based ILs, the process shows close to ideal electrochemical reversibility as the reaction between 1+ and [NTf2] anion is very slow. On the other hand, in tetrafluoroborate and trifluoromethanesulfonate-based IL, the oxidation of 1 shows different levels of electrochemical reversibility with a marked sign of anion attack to 1+. In contrast, 1 exhibits an irreversible oxidation process in hexafluorophosphate-based IL. The reaction rate constants for the interaction of 1+ with the different IL anions were estimated by fitting the experimental data to digital simulations of the proposed mechanism. Besides, the use of [NTf2]-based ILs as a supporting electrolyte in CH2Cl2 was also examined. The oxidation process of 1 shows a close to ideal electrochemical reversibility but low to non-chemical reversibility. This study illustrates the wide range of electrochemical environments available with ILs and demonstrates their limited utility for investigating the redox properties of metal carbonyl compounds. It also intends to warn the reader on how the IL media may influence an electrochemical study if care is not exercised. [ABSTRACT FROM AUTHOR]

The title compound, alternatively called (4‐bromophenyl)dihydrido(triphenylphosphanyl)boron, C24H21BBrP, crystallizes in the space group P with one symmetry‐independent molecule in the asymmetric unit. The B and P atoms both adopt the expected tetrahedral geometry. A possible intramolecular B—Hδ−...δ+H—C dihydrogen bond exists between an arene group on phosphorus and the borane center. In the solid state, the title molecule is connected to its neighbors by intermolecular C—H...π interactions, with the arene rings on the P atom acting as hydrogen‐bond donors and the arene ring of the borane acting as the acceptor. Hirshfeld analysis supports the existence of these interactions, as well as weak Br...Br interactions between neighboring molecules. [ABSTRACT FROM AUTHOR]

The hydrogen evolution and dendrite issues are the notorious culprits of the limited lifespan and Coulombic efficiency (CE) of Zn anodes, particularly at harsh test conditions. Herein, considering the Lewis acidic feature of Zn2+, abundant unshared pair electrons of zincophilic Lewis bases are proposed as decent electrolyte additives to stabilize Zn anodes at "Three High" conditions (high depth of discharge, high areal capacity and high current). The unshared pair electrons can remove H2O from Zn2+ solvated sheaths and confine the activity of H2O by breaking its hydrogen bonding network. The combination of these factors effectively restricts H2O‐involved side reactions and enables dendrite‐free Zn deposition, even at harsh conditions. The effectiveness of this strategy is fully proved by a series of Lewis base molecules. Noticeably, the Zn||Zn cell with an area of 20 cm2, using DMF‐containing electrolyte can be stably cycled over 1000 h at 60 % DOD, with a 100 % CE. [ABSTRACT FROM AUTHOR]

The utilization of CO2 attracts much research attention because of global warming. The CO2/epoxide cycloaddition reaction is one technique of CO2 utilization. However, homogeneous catalysts with both Lewis acidic and basic and toxic solvents, such as DMF, are needed in the CO2/epoxide cycloaddition reaction. As a result, this study focuses on the development of heterogeneous catalysts with both Lewis acidic and basic sites for the CO2 utilization of the CO2/epoxide cycloaddition reactions without the addition of a DMF toxic solvent. For the first time, the Zr–Mg mixed oxide aerogels with Lewis acidic and basic sites are synthesized for the CO2/propylene oxide (PO) cycloaddition reactions. To further increase the basic sites, 3-Aminopropyl trimethoxysilane (APTMS) with -NH2 functional group is successfully grafted on the Zr–Mg mixed oxide aerogels. The results indicate that the highest yield of propylene carbonate (PC) is 93.1% using the as-developed APTMS-modified Zr–Mg mixed oxide aerogels. The as-prepared APTMS-modified Zr–Mg mixed oxide aerogels are great potential in industrial plants for CO2 reduction in the future. [ABSTRACT FROM AUTHOR]

While the addition of C1‐Lewis base enolates to carbonyls and related structures are well established, the related addition to thiocarbonyls compounds are unknown. Herein, we report a reaction cascade in which a C1‐pyridinium enolate undergos addition to dithioesters, trithiocarbonates and xanthates. The reaction provides access to a range of dihydrothiophenes and dihydrothiopyrans (28‐examples). Mechanistic investigations, including isolation of intermediates, electronic correlation, and kinetic isotope effect studies support the viability of an activated acid intermediate giving rise to the C1‐pyridinium enolate which undergoes turnover limiting cyclization. Subsequent formation of a β‐thiolactone regenerates the catalyst with loss of carbon oxysulfide providing the observed products. [ABSTRACT FROM AUTHOR]

All-inorganic CsPbBr3 perovskite is an attractive emission material for high-stability perovskite light-emitting diodes (PeLEDs), due to the high thermal and chemical stability. However, the external quantum efficiencies (EQEs) of CsPbBr3 based PeLEDs are still far behind their organic–inorganic congeners. Massive defect states on the surface of CsPbBr3 perovskite grains should be the main reason. Lewis base additives have been widely used to passivate surface defects. However, systematic investigations which relate to improving the passivation effect via rational molecule design are still lacking. Here, we demonstrate that the CsPbBr3 film’s optical and electrical properties can be significantly boosted by tailoring the hardness–softness of the Lewis base additives. Three carboxylate Lewis bases with different tail groups are selected to in-situ passivate CsPbBr3 perovskite films. Our research indicates that 4-(trifluoromethyl) benzoate acid anion (TBA−) with the powerful electron-withdrawing group trifluoromethyl and benzene ring possesses the softest COO− bonding head. TBA− thus acts as a soft Lewis base and possesses a robust combination with unsaturated lead atoms caused by halogen vacancies. Based on this, the all-inorganic CsPbBr3 PeLEDs with a maximum EQE up to 16.75% and a half-lifetime over 129 h at an initial brightness of 100 cd m−2 is thus delivered.

Electron transport materials (ETMs) play a vital role in electron extraction and transport at the perovskite/ETM interface of inverted perovskite solar cells (PSCs) and are useful in power conversion efficiency (PCE), which is limited by interface carrier recombination. However, strategies for passivating undercoordinated Pb2+ at the perovskite/ETM interface employing ETMs remain a challenge. In this work, a variety of heteroatoms were used to strengthen the Lewis base property of new ETMs (asymmetrical perylene-diimide), aimed at deactivating non-bonded Pb2+ at the perovskite surface through Lewis acid-base coordination. Quantum chemical analysis revealed that novel ETMs have matched the energy level of perovskite, which enables electron extraction at the perovskite/ETM interface. The results also suggest that the large electron mobility (0.57~5.94 cm2 V−1 s−1) of designed ETMs shows excellent electron transporting ability. More importantly, reinforced interaction between new ETMs and Pb2+ was found, which is facilitating to passivation of the defects induced by unsaturated Pb2+ at the perovskite/ETM interface. Furthermore, it is found that MA (CH3NH3+), Pb, and IPb (iodine substituted on the Pb site) defects at the perovskite/ETM interface could be effectively deactivated by the new ETMs. This study provides a useful strategy to design ETMs for improving the interface property in PSCs.

Perovskite Solar Cells are a promising solar energy harvesting technology due to their low cost and high-power conversion efficiency. A high-quality perovskite layer is fundamental for a highly efficient perovskite Solar Cell. Utilizing a gas quenching process (GQP) can eliminate the need for toxic, flammable, and expensive anti-solvents in the preparation of perovskite layers. It is a promising candidate technology for large scale preparation of perovskite layers, as it can be easily integrated in a production line by coupling up-scalable techniques. The GQP removes the need for polar solvents in the precursor solution layer by using nitrogen flow, rather than extracting them with non-polar solvents. The crystallization dynamics in this process can be significantly different. In this study, we found that the quality of perovskite crystal from GQP is much more sensitive to Lewis base molecules (LBMs) in the precursor solution than it is in anti-solvents technology. Thus, the processing parameters of the LBMs in anti-solvents technology cannot be directly transferred to the GQP. An XRD and 1H NMR study explains the origin of the S-shaped J–V curves and how these LBMs hinder the reaction between PbI2 and monovelent cations. [ABSTRACT FROM AUTHOR]

In order to improve the pretreatment behavior of neutral deep eutectic solvent (DES), a novel method was proposed by using three types of Lewis base (sodium carbonate, sodium sulfite and sodium acetate as catalysts to pretreat corn straw at 120 °C for 3 h. As compared to DES, DES with Na 2 SO 3 , DES with NaAC and DES with Na 2 CO 3 , all can remove most of hemicellulose and lignin in pretreated corn straw. Meanwhile, the 94.5% of glucose yield was obtained treated by DES with Na 2 CO 3 and was approximately five-fold higher than that of the untreated substrate at an enzyme loading of 15 FPU/g material. The regenerated lignin displayed well-preserved structures, and possessed a high purity (more than 84%), narrow molecular weight distribution (PDI <2.4), excellent thermal stability. Overall, this work provided detailed analysis for efficient deconstruction of corn straw for future industrialized application. [Display omitted] • Lewis base enhanced neutral DES pretreatment was proposed. • DES with Lewis base approvingly retained most of cellulose in pretreated corn straw. • 88.1% of lignin was removed by Na2CO3 catalyzed ChCl/EG treatment. • Sugar yield was significantly increased from 17.9% to 94.5% in the saccharification process. • A high-quality lignin stream was obtained. [ABSTRACT FROM AUTHOR]

Lewis base catalysis provides powerful synthetic strategies for the selective construction of carbon‐carbon and carbon‐heteroatom bonds. Thus continuous efforts have been deployed to develop effective methodologies involving Lewis base catalysis. The nucleophilicity and steric hindrance of Lewis base catalyst often plays a major role in catalytic reactivity and selectivity in the reaction. In the past decades, tremendous progress has been made in the divergent construction of valuable motifs under Lewis base catalysis. In this review, we provide a comprehensive and updated summary of Lewis base‐catalysed chemo‐, diastereo‐ and enantiodivergent reaction, as well as the related mechanism will be highlighted in detail. [ABSTRACT FROM AUTHOR]

The Group 15 Pn(I) cations (Pn=N, P, As, Sb and Bi), which are isoelectronic with the donor‐stabilized carbones, have emerged recently. Despite the presence of two lone pair of electrons, the Pn(I) cations are weakly nucleophilic due to their inherent positive charge. Strongly electron‐donating supporting ligands including zwitterionic forms have been used to enhance their Lewis basicity. Furthermore, the chelating effect of cyclic ligand systems proved effective in increasing their nucleophilicity. The strategies involved in successfully isolating the fleeting Sb(I) and Bi(I) cations as the recent most achievements in this field have been discussed. The syntheses, structure, bonding situations and reactivity of the Pn(I) cations are discussed. An outlook on the periodic trends and future applications of these electronically unique electron‐rich cationic moieties have been provided. [ABSTRACT FROM AUTHOR]

As an atom-economical reaction, the direct generation of dimethyl carbonate (DMC) and ethylene glycol (EG) via the transesterification of CH 3 OH and ethylene carbonate (EC) has several promising applications, but the exploration of carriers with high specific surface areas and novel heterogeneous catalysts with more basic sites remains a long-standing research challenge. For this purpose, herein, a nitrogen-doped mesoporous carbon (NMC, 439 m 2 /g) based K-O 2 Lewis base catalyst (K-O 2 /NMC) with well-dispersed strongly basic sites (2.23 mmol/g, 84.5%) was designed and synthesized. The compositions and structures of NMC and K-O 2 /NMC were comprehensively investigated via Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, N 2 adsorption-desorption, CO 2 temperature-programmed desorption, and contact angle measurements. The optimal structural configuration and electron cloud distribution of the K-O 2 /NMC catalyst were simulated using first-principles calculations. The electron transfer predominantly manifested as a flow from K-O to C-O/C-N, and the interatomic interactions between each atom were enhanced and exhibited a tendency for a more stable state after redistribution. Furthermore, the adsorption energies ( E ads ) of CH 3 OH at K-O-O and K-O-N sites were -1.4185 eV and -1.3377 eV, respectively, and the O atom in CH 3 OH exhibited a stronger adsorption tendency for the K atom at the K-O-O site. Under the optimal conditions, the EC conversion, DMC/EG selectivity, and turnover number/frequency were 80.9%, 98.6%/99.4%, and 40.5/60.8 h -1 , respectively, with a reaction rate constant (k) of 0.1005 mol/(L·min). Results showed that the heterogeneous K-O 2 /NMC catalyst prepared herein greatly reduced the reaction cost while guaranteeing the catalytic effect, and the whole system required a lower reaction temperature (65 °C), a shorter reaction time (40 min), and a lower catalyst amount (2.0 wt % of EC). Therefore, K-O 2 /NMC can be used as a catalyst in different transesterification reactions.

Lewis base molecules bind the undercoordinated lead atoms at interfaces and grain boundaries, leading to the high efficiency and stability of flexible perovskite solar cells (PSCs). We demonstrated a highly efficient, stable, and flexible PSC via interface passivation using a Lewis base of tri( o -tolyl)phosphine (TTP). It not only induced an intimate interface contact and a complete deposition of the perovskite thin layers on hole transport layers (HTLs) but also led to a better perovskite with a raised crystallinity, fewer defects, and a better morphology, including fewer gullies, high uniformity, and low roughness. Furthermore, the TTP treatments induced a good alignment of energy levels among the perovskites, HTLs, and C 60 . The resultant flexible inverted PSCs exhibited a high power conversion efficiency (PCE) of 23.81%, which is one of the highest PCEs among these flexible inverted PSCs. Moreover, the optimized flexible PSCs exhibited high storage stability, superior operation stability, and enhanced mechanical flexibility. This study presents an effective method to substantially raise the PCE, stability, and mechanical flexibility of the flexible inverted perovskite photovoltaics.

For resolving toxicity issues of Pb‐based perovskites, Sn‐based perovskites have been widely studied as a promising alternative due to similar valence electron configuration between Sn2+ and Pb2+. However, desired Sn2+ in the precursor solution and film is easily oxidized to Sn4+, causing detrimental Sn vacancies and impurities in the films. Unfortunately, dimethyl sulfoxide, a ubiquitously used Lewis base for the fabrication of high‐quality perovskite thin films via the adduct approach, further accelerates the oxidation of Sn2+ in the precursor solution. Herein, N,N′‐dimethylpropyleneurea (DMPU) is proposed as an alternative Lewis base for the fabrication of high‐quality Sn‐based perovskite thin films. The strongly coordinating Lewis base DMPU is shown to suppress the oxidation of Sn2+ in the precursor solution while promoting growth of uniform and highly crystalline thin films. The PEA2SnI4 perovskite light emitting diode (PeLED) based on DMPU demonstrates dramatically improves luminance (L): a more than sixfold enhanced external quantum efficiency (EQE) and better operational stability than those of the device fabricated without DMPU. The optimum PeLED based on DMPU achieves a maximum L and EQE of 68.84 cd m−2 and 0.361%, respectively. This study provides an important methodological base for studying Sn perovskites for development of high‐performance and eco‐friendly PeLEDs. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: The first asymmetric decarboxylative [3+2]‐cycloaddition of ethynyl indoloxazolidones with carboxylic acids has been developed under synergistic catalysis of copper and chiral Lewis base. This protocol provides a direct and modular approach to biologically important pyrrolo[1,2‐a]indoles bearing two vicinal stereogenic centers with excellent diastereo‐ and enantioselectivities (up to >20 : 1 dr and >99% ee). In addition, the utility of this methodology was demonstrated by scaled‐up reaction and several synthetic transformations of the cycloadduct. [ABSTRACT FROM AUTHOR]

Solvent engineering by Lewis‐base solvent and anti‐solvent is well known for forming uniform and stable perovskite thin films. The perovskite phase crystallizes from an intermediate Lewis‐adduct upon annealing‐induced crystallization. Herein, it is explored the effects of trimethyl phosphate (TMP), as a novel aprotic Lewis‐base solvent with a low donor number for the perovskite film formation and photovoltaic characteristics of perovskite solar cells (PSCs). As compared to dimethylsulfoxide (DMSO) or dimethylformamide (DMF), the usage of TMP directly crystallizes the perovskite phase, i.e., reduces the intermediate phase to a negligible degree, right after the spin‐coating, owing to the high miscibility of TMP with the anti‐solvent and weak bonding in the Lewis adduct. Interestingly, the PSCs based on methylammonium lead iodide (MAPbI3) derived from TMP/DMF‐mixed solvent exhibit a higher average power conversion efficiency of 19.68% (the best: 20.02%) with a smaller hysteresis in the current‐voltage curve, compared to the PSCs that are fabricated using DMSO/DMF‐mixed (19.14%) or DMF‐only (18.55%) solvents. The superior photovoltaic properties are attributed to the lower defect density of the TMP/DMF‐derived perovskite film. The results indicate that a high‐performance PSC can be achieved by combining a weak Lewis base with a well‐established solvent engineering process. [ABSTRACT FROM AUTHOR]

Three MgCl2 supported TiCl4 pro-catalysts; Cat-A, Cat-B and Cat-C were synthesized. Cat-A was synthesized without any internal Lewis base (ILB); while Cat-B and Cat-C were synthesized using diisobutyl phthalate and ethyl benzoate as ILBs respectively. The effect of ILBs on stereoregularity and the microstructure of polybutadiene (PBD) was investigated. The vast differences in the amount of trans-1,4-structure of PBD by Cat-A, Cat-B and Cat-C systems were correlated with the nature of ILBs used by studying their polymerization kinetics. The energy barriers for polymerization reactions were calculated for all three catalysts systems using Arrhenius equation. Cat-B, has shown the highest energy barrier (23 kJ/mol) due to DIBP as ILB in its structure. Cat-A has given the lowest trans-1,4-PBD as it does not contain any ILB and has the minimum energy barrier (12 kJ/mol) while Cat-C has shown medium energy barrier (17 kJ/mol). We have also studied the effect of suitable external Lewis bases during polymerization. The effect of polymerization parameters like Al/Ti molar ratio, Al/LB molar ratios and the temperatures on PBD microstructure were studied. Based on the polymerization kinetics studies and the effect of LBs on PBD microstructure, a possible reaction mechanism has been proposed. [ABSTRACT FROM AUTHOR]

This Minireview provides insight into the early history of nucleophilic phosphinocatalysis. The concepts of 1,4‐addition of a tertiary phosphine to an α,β‐enone and of equilibrium between the resulting phosphonium zwitterion and phosphonium ylide established a fundamental basis for the development of several classical transformations, including the Rauhut‐Currier, Morita, McClure‐Baizer‐Anderson, and Oda reactions. [ABSTRACT FROM AUTHOR]

Abstract Solvent engineering by Lewis‐base solvent and anti‐solvent is well known for forming uniform and stable perovskite thin films. The perovskite phase crystallizes from an intermediate Lewis‐adduct upon annealing‐induced crystallization. Herein, it is explored the effects of trimethyl phosphate (TMP), as a novel aprotic Lewis‐base solvent with a low donor number for the perovskite film formation and photovoltaic characteristics of perovskite solar cells (PSCs). As compared to dimethylsulfoxide (DMSO) or dimethylformamide (DMF), the usage of TMP directly crystallizes the perovskite phase, i.e., reduces the intermediate phase to a negligible degree, right after the spin‐coating, owing to the high miscibility of TMP with the anti‐solvent and weak bonding in the Lewis adduct. Interestingly, the PSCs based on methylammonium lead iodide (MAPbI3) derived from TMP/DMF‐mixed solvent exhibit a higher average power conversion efficiency of 19.68% (the best: 20.02%) with a smaller hysteresis in the current‐voltage curve, compared to the PSCs that are fabricated using DMSO/DMF‐mixed (19.14%) or DMF‐only (18.55%) solvents. The superior photovoltaic properties are attributed to the lower defect density of the TMP/DMF‐derived perovskite film. The results indicate that a high‐performance PSC can be achieved by combining a weak Lewis base with a well‐established solvent engineering process.

The oxidative electrochemistry of cymantrene, CpMn(CO)3 (1; Cp = [η5-C5H5]–), was examined in ionic liquids (ILs) composed of anions of varying Lewis base properties. It was observed that the cyclic voltammetric responses strongly depended on the nucleophilic properties of the IL anion. Still, all observations are consistent with the initial formation of 1+ followed by an attack from the IL anion. In bis(trifluoromethylsulfonyl)amide [NTf2]-based ILs, the process shows close to ideal electrochemical reversibility as the reaction between 1+ and [NTf2] anion is very slow. On the other hand, in tetrafluoroborate and trifluoromethanesulfonate-based IL, the oxidation of 1 shows different levels of electrochemical reversibility with a marked sign of anion attack to 1+. In contrast, 1 exhibits an irreversible oxidation process in hexafluorophosphate-based IL. The reaction rate constants for the interaction of 1+ with the different IL anions were estimated by fitting the experimental data to digital simulations of the proposed mechanism. Besides, the use of [NTf2]-based ILs as a supporting electrolyte in CH2Cl2 was also examined. The oxidation process of 1 shows a close to ideal electrochemical reversibility but low to non-chemical reversibility. This study illustrates the wide range of electrochemical environments available with ILs and demonstrates their limited utility for investigating the redox properties of metal carbonyl compounds. It also intends to warn the reader on how the IL media may influence an electrochemical study if care is not exercised.

The utilization of CO2 attracts much research attention because of global warming. The CO2/epoxide cycloaddition reaction is one technique of CO2 utilization. However, homogeneous catalysts with both Lewis acidic and basic and toxic solvents, such as DMF, are needed in the CO2/epoxide cycloaddition reaction. As a result, this study focuses on the development of heterogeneous catalysts with both Lewis acidic and basic sites for the CO2 utilization of the CO2/epoxide cycloaddition reactions without the addition of a DMF toxic solvent. For the first time, the Zr–Mg mixed oxide aerogels with Lewis acidic and basic sites are synthesized for the CO2/propylene oxide (PO) cycloaddition reactions. To further increase the basic sites, 3-Aminopropyl trimethoxysilane (APTMS) with -NH2 functional group is successfully grafted on the Zr–Mg mixed oxide aerogels. The results indicate that the highest yield of propylene carbonate (PC) is 93.1% using the as-developed APTMS-modified Zr–Mg mixed oxide aerogels. The as-prepared APTMS-modified Zr–Mg mixed oxide aerogels are great potential in industrial plants for CO2 reduction in the future.