Lewis Acid Research Articles

Effect of sulfation on the catalytic performance of Mn-Co composite oxide catalyst for the selective catalytic reduction of NOx by NH3

The effect of sulfation on the catalytic performance of Mn-Co composite oxide catalyst for the selective catalytic reduction of NOx by NH3 (NH3-SCR) has been investigated. Different concentrations of SO2 have been used to sulfate Mn-Co composite oxide catalyst. The catalyst sulfated with 30 ppm SO2 showed the widest activity temperature window, over which 80% NOx conversion was obtained in the temperature range of 80–350 °C. The sulfation leads to the appropriate redox property of Mn-Co composite oxide, thus improving the N2 selectivity. Meanwhile, the sulfation contributes to the generation of more Brønsted acid sites, which is crucial for the enhanced activity. In situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS) demonstrated that the adsorbed NH3 species on both Lewis acid and Brønsted acid sites, monodentate nitrite, bidentate nitrate and cis-nitrite species are the reactive intermediates in the NH3-SCR reaction. This study provides an idea for the regulating the activity temperature window of NH3-SCR catalyst to adapt to its practical application.

Engineering H2O2 Self-Supplying Platform for Xdynamic Therapies via Ru-Cu Peroxide Nanocarrier: Tumor Microenvironment-Mediated Synergistic Therapy.

Of the most common, hypoxia, overexpressed glutathione (GSH), and insufficient H2O2 concentration in the tumor microenvironment (TME) are the main barriers to the advancment of reactive oxygen species (ROS) mediated Xdynamic therapies (X = photo, chemodynamic, chemo). Maximizing Fenton catalytic efficiency is crucial in chemodynamic therapy (CDT), yet endogenous H2O2 levels are not sufficient to attain better anticancer efficacy. Specifically, there is a need to amplify Fenton reactivity within tumors, leveraging the unique attributes of the TME. Herein, for the first time, we design RuxCu1-xO2-Ce6/CPT (RCpCCPT) anticancer nanoagent for TME-mediated synergistic therapy based on heterogeneous Ru-Cu peroxide nanodots (RuxCu1-xO2 NDs) and chlorine e6 (Ce6), loaded with ROS-responsive thioketal (TK) linked-camptothecin (CPT). The Ru-Cu peroxide NDs (RCp NDs, x = 0.50) possess the highest oxygen vacancy (OV) density, which grants them the potential to form massive Lewis's acid sites for peroxide adsorption, while the dispersibility and targetability of the NDs were improved via surface modification using hyaluronic acid (HA). In TME, RCpCCPT degrades, releasing H2O2, Ru2+/3+, and Cu+/2+ ions, which cooperatively facilitate hydroxyl radical (•OH) formation and deactivate antioxidant GSH enzymes through a cocatalytic loop, resulting in excellent tumor therapeutic efficacy. Furthermore, when combined with laser treatment, RCpCCPT produces singlet oxygen (1O2) for PDT, which induces cell apoptosis at tumor sites. Following ROS generation, the TK linkage is disrupted, releasing up to 92% of the CPT within 48 h. In vitro investigations showed that laser-treated RCpCCPT caused 81.5% cell death from PDT/CDT and chemotherapy (CT). RCpCCPT in cancer cells produces red-blue emission in images of cells taking them in, which allows for fluorescence image-guided Xdynamic treatment. The overall results show that RCp NDs and RCpCCPT are more biocompatible and have excellent Xdynamic therapeutic effectiveness in vitro and in vivo.

Catalytic Hydroconversion of Lauric Acid Over Poly(N-vinyl-2-pyrrolidone)-Coated Pd Nanoparticles on ZIF-8

A subclass of Metal-Organic Frameworks, Zeolitic Imidazole Frameworks-8 (ZIF-8) is known as an emerging material that has the characteristic of a large surface area, good thermal stability as well as a high porosity. Instead of having extraordinary properties, ZIF-8 consists of Lewis acid and Lewis base site on its Zn metals and 2-methylimidazole which are the important components for the catalyst. In this study, Pd-Poly(N-vinyl-2-pyrrolidone) coated on ZIF-8 (Pd-PVP@ZIF-8) was synthesized by mixed Pd-PVP solution and ZIF-8 precursors at room temperature. The Pd-PVP solution was varied from 10 to 50 ml to differentiate the Pd concentration in ZIF-8. As-synthesized 50 ml of Pd-PVP on ZIF-8 (50Pd-PVP@ZIF-8) showed catalytic activity in the conversion of 98.6% lauric acid to produce 78.2% of 1-dodecanol at optimum condition 320 °C for 6 h. The synergy between Pd-PVP as metal and ZIF-8 as metal support as well as high dispersion of Pd particles could enhance performance in the conversion of lauric acid. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Oxygen-Vacancy-Mediated Large Binding Energy Exciton Dissociation in Nb3O7(OH) Nanorods with High Electron Mobility for CO2 Photoreduction.

Despite the excellent performance of Nb3O7(OH) in dye-sensitized solar cells and catalysis, its charge separation, transport, and structural properties remain poorly understood. Herein, the Nb3O7(OH) nanorods were prepared, and their structural characteristics, optoelectronic properties, and carrier mobility were also analyzed and investigated through a series of complex characterizations. Theoretical prediction suggested that the exciton binding energy of Nb3O7(OH) could be as high as 100.49 meV. The temperature-dependent photoluminescence (PL) of Nb3O7(OH) nanorods revealed two activation energies, and a higher proportion of long-lived components observed in the photoluminescence decay indicated effective electron trapping. That is, two energy states were present, hindering photogenerated charge recombination and promoting photocatalytic action. Current-voltage characteristics of the Nb3O7(OH) nanorod film were analyzed, revealing an ultrahigh carrier mobility of ∼310 cm2/V·s, ensuring fast and efficient electron transfer. Furthermore, Nb3O7(OH) nanorods were employed to reduce CO2, resulting in the effective production of CO and CH4. Overall, considering the presence of hydroxyl pairs on the surface of Nb3O7(OH), which facilitate the formation of the frustrated Lewis acid-base pairs and the activation of CO2, together with its effective electron trapping and charge transport, give Nb3O7(OH) nanorods a promising potential for CO2 reduction.

Comparative Selective Conversion of Biomass-Derived Mono- and Polysaccharides into Lactic Acid with Lanthanide Lewis Acid Catalysts

Comparative Selective Conversion of Biomass-Derived Mono- and Polysaccharides into Lactic Acid with Lanthanide Lewis Acid Catalysts

Bimetallic [Ge-Rh] complex catalyzed alkyne semihydrogenation: Theoretical investigations on the germanium promoted mechanism and selectivity

Transitional metal catalyzed alkynes functionalization is a very important method to obtain the organic intermediates. In this work, the mechanism of PhCCPh hydrogenation catalyzed by [Ge-Rh] bimetallic catalyst has been studied by means of density functional theory. The whole reaction consists of two cycles, cis-semihydrogenation of alkyne to give Z-alkene and trans-isomerization to get E-alkene. The rate-determining step is the hydrogen complexation in cis-semihydrogenation. Because the isomerization from Z-alkene to E-alkene is easy, while the reverse transformation is difficult, E-alkene is main product of alkyne semihydrogenation. The semihydrogenation would be facilitated by replacing the terphenyl ligands in the [Ge-Rh] bimetallic catalyst with the polar N-heterocyclic ligands. The addition of H2 is crucial in controlling the chemoselectivity of the reaction. The Ge acts as the Lewis acid to reduce the electron density on Rh, making Rh center becomes more electropositive than that in the monorhodium catalysts, thus increasing the selectivity of the [Ge-Rh] bimetallic catalyst. Our work elucidates the detailed mechanism of PhCCPh semihydrogenation catalyzed by the [Ge-Rh] catalyst and provides explanations for the experimental results.

Coordination Variations within Binuclear Copper Dioxygen-Derived (Hydro)Peroxo and Superoxo Species; Influences upon Thermodynamic and Electronic Properties.

Copper ion is a versatile and ubiquitous facilitator of redox chemical and biochemical processes. These include the binding of molecular oxygen to copper(I) complexes where it undergoes stepwise reduction-protonation. A detailed understanding of thermodynamic relationships between such reduced/protonated states is key to elucidate the fundamentals of the chemical/biochemical processes involved. The dicopper(I) complex [CuI2(BPMPO-)]1+ {BPMPOH = 2,6-bis{[(bis(2-pyridylmethyl)amino]methyl}-4-methylphenol)} undergoes cryogenic dioxygen addition; further manipulations in 2-methyltetrahydrofuran generate dicopper(II) peroxo [CuII2(BPMPO-)(O22-)]1+, hydroperoxo [CuII2(BPMPO-)(-OOH)]2+, and superoxo [CuII2(BPMPO-)(O2•-)]2+ species, characterized by UV-vis, resonance Raman and electron paramagnetic resonance (EPR) spectroscopies, and cold spray ionization mass spectrometry. An unexpected EPR spectrum for [CuII2(BPMPO-)(O2•-)]2+ is explained by the analysis of its exchange-coupled three-spin frustrated system and DFT calculations. A redox equilibrium, [CuII2(BPMPO-)(O22-)]1+ ⇄ [CuII2(BPMPO-)(O2•-)]2+, is established utilizing Me8Fc+/Cr(η6-C6H6)2, allowing for [CuII2(BPMPO-)(O2•-)]2+/[CuII2(BPMPO-)(O22-)]1+ reduction potential calculation, E°' = -0.44 ± 0.01 V vs Fc+/0, also confirmed by cryoelectrochemical measurements (E°' = -0.40 ± 0.01 V). 2,6-Lutidinium triflate addition to [CuII2(BPMPO-)(O22-)]1+ produces [CuII2(BPMPO-)(-OOH)]2+; using a phosphazene base, an acid-base equilibrium was achieved, pKa = 22.3 ± 0.7 for [CuII2(BPMPO-)(-OOH)]2+. The BDFEOO-H = 80.3 ± 1.2 kcal/mol, as calculated for [CuII2(BPMPO-)(-OOH)]2+; this is further substantiated by H atom abstraction from O-H substrates by [CuII2(BPMPO-)(O2•-)]2+ forming [CuII2(BPMPO-)(-OOH)]2+. In comparison to known analogues, the thermodynamic and spectroscopic properties of [CuII2(BPMPO-)] O2-derived adducts can be accounted for based on chelate ring size variations built into the BPMPO- framework and the resulting enhanced CuII-ion Lewis acidity.

Catalytic 1,1-diazidation of alkenes.

Compared to well-developed catalytic 1,2-diazidation of alkenes to produce vicinal diazides, the corresponding catalytic 1,1-diazidation of alkenes to yield geminal diazides has not been realized. Here we report an efficient approach for catalytic 1,1-diazidation of alkenes by redox-active selenium catalysis. Under mild conditions, electron-rich aryl alkenes with Z or E or Z/E mixed configuration can undergo migratory 1,1-diazidation to give a series of functionalized monoalkyl or dialkyl geminal diazides that are difficult to access by other methods. The method is also effective for the construction of polydiazides. The formed diazides are relatively safe by TGA-DSC analysis and impact sensitivity tests, and can be easily converted into various valuable molecules. In addition, interesting reactivity that geminal diazides give valuable molecules via the geminal diazidomethyl moiety as a formal leaving group in the presence of Lewis acid is disclosed. Mechanistic studies revealed that a selenenylation-deselenenylation followed by 1,2-aryl migration process is involved in the reactions, which provides a basis for the design of new reactions.

Electrografting of aryl amines on graphitic surfaces: An alternative to diazonium salts?

Aryl amines have recently been shown to be effectively grafted with the use of Lewis bases. Hence, they have been proposed as a potential alternative to aryl diazonium salts for the covalent modification of surfaces. In this work we compare grafting efficiencies of aryl amines, such as 4-bromoaniline (4-BA), with aryl diazonium salts, such as 4-bromobenzene diazonium (4-BBD), on carbon-based surfaces, namely highly oriented pyrolytic graphite (HOPG) and graphene. The Lewis base 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was employed to improve the grafting of 4-BA to the surfaces. The systems were studied with a range of techniques to confirm grafting of the organic molecules to the carbon surfaces, such as cyclic voltammetry, atomic force microscopy, scanning tunnelling microscopy and Raman spectroscopy. Density functional theory calculations demonstrate that the C-C bond is more favoured than the C-N bond. The grafting density of the aryldiazonium salts on graphite and graphene surfaces is much higher compared to aryl amines with or without the use of a Lewis base. Consequently, selection of the appropriate precursor for efficient covalent functionalization of a surface is required.

Hydroconversion of lignin-derived platform compound guaiacol to fuel additives and value-added chemicals over alumina-supported Ni catalysts

Hydroconversion of guaiacol (GUA) over γ-Al2O3 and phosphatized-γ-Al2O3 (γ-Al2O3(P)) supported Ni catalysts was initiated by Lewis-sites and active Ni sites. Conversion proceeded via transmethylation and hydrodemethylation/hydrodemethoxylation as major and minor pathways, respectively, resulting in mainly catechol and methylcatechols, and via series of consecutive hydrodehydroxylation (HDHY) and ring hydrogenation (HYD) reactions leading to partially and fully deoxygenated, saturated, and unsaturated products. High Ni-loading and high H2 pressure promoted the formation of cyclohexane and methyl-substituted cyclohexanes; however, above 300 °C the hydrogenation–dehydrogenation equilibrium favored the formation of benzene and methyl-substituted benzenes. Ni/γ-Al2O3(P) showed suppressed HYD/HDHY activity resulting in pronounced formation of catechol and/or phenol and their methyl-substituted derivatives. Surface phenolate species were substantiated as surface intermediates of hydrodeoxygenation. Phosphatizing reduced the concentration of both basic OH and Lewis acid (Al+) – Lewis base (O–) pair surface sites of the γ-Al2O3 support and, thereby, suppressed phenolate formation and hydrodeoxgenation.

Benzoxaborole Catalyst Embedded with a Lewis Base: A Highly Active and Selective Catalyst for cis-1,2-diol Modification.

The regioselective modification of polyols allows rapid access to their derivatives, thereby accelerating the polyol-related biology and drug discovery. We previously reported that benzoxaborole is a potent catalyst for the regioselective modification of polyols containing a cis-1,2-diol structure. In this study, we developed a bifunctional benzoxaborole catalyst embedded with a Lewis base. Benzoxaborole and Lewis base groups were designed to cooperatively activate a substrate (cis-1,2-diol) and reactant (electrophile), respectively, hence lowering the reaction barrier for the cis-1,2-diol moiety. The bifunctional catalyst indeed exhibited a significantly higher catalytic activity and selectivity for cis-1,2-diol modifications rather than a benzoxaborole catalyst without a Lewis base group. Mechanistic analyses, using both experimental and theoretical methods, supported the design of our catalyst. The bifunctional catalyst reported herein would be a new tool for the straightforward synthesis of polyol derivatives.

Performance of removing aqueous contaminant by zirconium based adsorbents: a critical review

The studies on materials for decontamination in aqueous solutions have increasingly received greater attentions. Such contaminants as heavy metals, arsenic, fluoride and phosphate are harmful to humans and aqueous species due to higher toxicity. Zirconium based adsorbents have become more attractive due to outstanding performance in decontamination. This article provides a comprehensive review of the performance and mechanisms of five types adsorbents: zirconium (hydro)oxides, zirconium hydrogen sulfate, zirconium based multiple metal typed adsorbents and zirconium impregnated complexes. The pseudo-first order and pseudo-second order equations and the intraparticle diffusion model can be applied in describing the adsorption kinetics, while Langmuir and Freundlich equations are the most commonly used adsorption isotherms. The important mechanisms for uptake of contaminants are: ligand exchange between adsorbate and adsorbent, surface complexation formation, and Lewis acid–base and electrostatic interactions. A series of successful studies demonstrate that the adsorbents are promising for removing aqueous contaminants.

Carbene-catalyzed and Pnictogen Bond-assisted Access to PIII-Stereogenic Compounds.

Intermolecular pnictogen bonding (PnB) catalysis has received increased interest in non-covalent organocatalysis. It has been demonstrated that organic electron-deficient pnictogen atoms can act as prospective Lewis acids. Here, we present a catalytic approach for the asymmetric synthesis of chiral PIII compounds by combining intramolecular PnB interactions and carbene catalysis. Our design features a pre-chiral phosphorus molecules bearing two electron-withdrawing benzoyl groups, resulting in the formation of a σ-hole at the P atom. X-ray and non-covalent interaction (NCI) analysis indicate that these phosphorus substrates exhibit intrinsic PnB interactions between the oxygen atom of the formyl group and the phosphorus atom. This induces a conformational locking effect, leading to the crystallization of the phosphorus substrates in a preferred conformation (P212121 chiral group). Under the catalysis of N-heterocyclic carbene, the aldehyde moiety activated by the pnictogen bond selectively reacts with an alcohol to yield the corresponding chiral monoester/phosphorus products with excellent enantioselectivity. This Lewis acidic phosphorus center, aroused by the non-polarized intramolecular pnictogen bond interaction, assists in conformational and selective regulations, providing unique opportunities for catalysis and beyond.

Carbene‐catalyzed and Pnictogen Bond‐assisted Access to PIII‐Stereogenic Compounds

Intermolecular pnictogen bonding (PnB) catalysis has received increased interest in non‐covalent organocatalysis. It has been demonstrated that organic electron‐deficient pnictogen atoms can act as prospective Lewis acids. Here, we present a catalytic approach for the asymmetric synthesis of chiral PIII compounds by combining intramolecular PnB interactions and carbene catalysis. Our design features a pre‐chiral phosphorus molecules bearing two electron‐withdrawing benzoyl groups, resulting in the formation of a σ‐hole at the P atom. X‐ray and non‐covalent interaction (NCI) analysis indicate that these phosphorus substrates exhibit intrinsic PnB interactions between the oxygen atom of the formyl group and the phosphorus atom. This induces a conformational locking effect, leading to the crystallization of the phosphorus substrates in a preferred conformation (P212121 chiral group). Under the catalysis of N–heterocyclic carbene, the aldehyde moiety activated by the pnictogen bond selectively reacts with an alcohol to yield the corresponding chiral monoester/phosphorus products with excellent enantioselectivity. This Lewis acidic phosphorus center, aroused by the non‐polarized intramolecular pnictogen bond interaction, assists in conformational and selective regulations, providing unique opportunities for catalysis and beyond.

Synthesis, Characterization and Reactivity Studies of Cobalt(III) Porphyrin‐Iodosylarene Adduct and Cobalt(III) Porphyrin π‐Cation Radical Species

AbstractBiomimetic metalloporphyrin complexes have been employed in a number of catalytic oxidation reactions by utilizing terminal oxidants such as iodosylarenes (ArIO). Although high‐valent metal‐oxo species have been considered as the reactive intermediates, their precursors, metal‐iodosylarene adduct species, also exhibit intriguing oxidation capability under certain conditions. However, late transition metal porphyrin‐oxidant adduct species have not been explored in oxidation reactions yet. Herein, we report the synthesis, characterization and reactivity studies of cobalt(III) porphyrin‐ArIO adduct complexes. These adduct species exhibit moderate oxidation capability in electron transfer reactions. More interestingly, addition of Brønsted acid or Lewis acid facilitated the O−I bond cleavage, resulted in the formation of cobalt(III) porphyrin π‐cation radical species, which is much more reactive than the corresponding adduct species in electron transfer reactions. Kinetic studies and theoretical calculations demonstrate that the O−I bond cleavage is triggered in the presence of acid, affording the porphyrin ligand oxidation while the formation of high‐valent cobalt‐oxo species is prohibited due to the “oxo‐wall” for late transition metals. This study provides a novel model of a late transition metal‐iodosylarene adduct species as an active oxidant in oxidation reactions, while in the cases of iron and manganese complexes, high‐valent metal‐oxo species are generated.

Synthesis of Al-containing Sn-beta with tunable brønsted and lewis acidity for conversion of glucose to 5-hydroxymethylfurfural

Sn–Al-Beta zeolites with less silanol defects were synthesized in fluoride media. The effects of the amount of organic template (tetraethylammonium hydroxide, TEAOH), mineralizer (NH4F), Al and Sn on the synthesis, acidity and catalytic performance were systematically studied. The synthesized Sn–Al-Beta zeolites were characterized by XRD, SEM, 27Al MAS NMR, UV–vis DRS and FT-IR spectroscopy of hydroxy region and pyridine adsorption. The optimum values of nTEAOH/nSi and nF-/nSi were same (0.3) for synthesizing Sn–Al-Beta with high crystallinity at 140 °C for 7 d. Moreover, decreasing nF-/nSi facilitated the incorporation of Al into the framework. The crystallization rate of Sn–Al-Beta is similar with that of Sn-Beta. Sn was promoted to enter the framework with the increase of Al content, while elevating Sn content has no effect on the incorporation of Al into the framework. The catalytic performance of Sn–Al-Beta was investigated for conversion of glucose to 5-hydroxymethylfurfural in water-containing solvent. Sn–Al-Beta synthesized in fluoride media is more stable than the post-synthesized sample.

Metal-Solvent Complex Formation at the Surface of InP Colloidal Quantum Dots.

The surface chemistry of colloidal semiconductor nanocrystals (QDs) profoundly influences their physical and chemical attributes. The insulating organic shell ensuring colloidal stability impedes charge transfer, thus limiting optoelectronic applications. Exchanging these ligands with shorter inorganic ones enhances charge mobility and stability, which is pivotal for using these materials as active layers for LEDs, photodetectors, and transistors. Among those, InP QDs also serve as a model for surface chemistry investigations. This study focuses on group III metal salts as inorganic ligands for InP QDs. We explored the ligand exchange mechanism when metal halide, nitrate, and perchlorate salts of group III (Al, In Ga), common Lewis acids, are used as ligands for the conductive inks. Moreover, we compared the exchange mechanism for two starting model systems: InP QDs capped with myristate and oleylamine as X- and L-type native organic ligands, respectively. We found that all metal halide, nitrate, and perchlorate salts dissolved in polar solvents (such as n-methylformamide, dimethylformamide, dimethyl sulfoxide, H2O) with various polarity formed metal-solvent complex cations [M(Solvent)6]3+ (e.g., [Al(MFA)6]3+, [Ga(MFA)6]3+, [In(MFA)6]3+), which passivated the surface of InP QDs after the removal of the initial organic ligand. All metal halide capped InP/[M(Solvent)6]3+ QDs show excellent colloidal stability in polar solvents with high dielectric constant even after 6 months in concentrations up to 74 mg/mL. Our findings demonstrate the dominance of dissociation-complexation mechanisms in polar solvents, ensuring colloidal stability. This comprehensive understanding of InP QD surface chemistry paves the way for exploring more complex QD systems such as InAs and InSb QDs.

Mechanistic Insights Into the [3+1] Cycloadditions of Me3SiN3 on Bis‐Silylene and the Formation of Pseudo‐Silaazatriene

AbstractThe reaction mechanism for the formation of the pseudo‐silaazatriene 1 (LN(SiMe3)2−Si−N−Si(L)NSiMe3; L=PhC−(NtBu)2) by the reaction of 1 equivalent of bis‐silylene (LSi−SiL; L=PhC(NtBu)2) with 3 equivalents of azide Me3SiN3 has been explored at M06/def2‐TZVPP//BP86‐D3(BJ)/def2‐TZVPP level of theory. The reaction mechanism is guided by the high Lewis basicity of the silicon lone pair and the high Lewis acidic character of Si−N bonds, as well as by the high tendency to eliminate N2 from Me3SiN3. The first step of the reaction is the formation of [3+1] cycloaddition product (I1) by the synergetic interactions of the lone pair on the silylene silicon with the π* molecular orbital of Me3SiN3 which is majorly localized on the terminal nitrogen atom, and the donation of the σ‐type lone pair on the nitrogen atom connected to the SiMe3 group with the Si−N σ* orbital on silylene. The elimination of N2 from I1 results in the formation of pseudo‐silaimine intermediate I2 having a dicoordinated, monovalent nitrogen atom. The most favourable pathway involves the second addition of Me3SiN3 followed by N2 elimination resulting bis‐silaimine intermediate I4‐P2. The highly reactive lone pair on the dicoordinated, monovalent nitrogen atom can be coordinated to the Si−N σ* MO of the second silylene moiety resulting in Si−N bond formation and Si−Si bond cleavage. This step is similar to the SN2′ reaction where the incoming nucleophile and the leaving group are on the same side resulting in the formation of silaimine I5. Further, the [3+1] cycloaddition of one more molecule of Me3SiN3 followed by N2 elimination results in the formation of silaimine intermediate I7. I7 undergoes 1,3‐silyl migration leading to the final product 1. The lone pairs on di‐ and tricoordinated nitrogen centres of all the intermediates are stabilized by hyperconjugative interactions. The delocalized hyperconjugative interaction stabilizes the lone pairs in 1.

Modulating Nucleation and Crystal Growth of Tin Perovskite Films for Efficient Solar Cells.

The performance of tin halide perovskite solar cells (PSCs) has been severely limited by the rapid crystallization of tin perovskites, which usually leads to an undesirable film quality. In this work, we tackle this issue by regulating the nucleation and crystal growth of tin perovskite films using a small Lewis base additive, urea. The urea-SnI2 interaction facilitates the formation of larger and more uniform clusters, thus accelerating the nucleation process. Additionally, the crystal growth process is extended, resulting in a high-quality tin perovskite film with compact morphology, increased crystallinity, and reduced defects. Consequently, the efficiency of tin PSCs is significantly increased from 10.42% to 14.22%. This work highlights the importance of manipulating the nucleation and crystal growth of tin perovskites to realize efficient tin PSCs.

Asymmetric catalysis by chiral FLPs: A computational mini-review.

Steric hindrance in Lewis acid (LA) and Lewis base (LB) obstruct the Lewis acid-base adduct formation, and the pair was termed as frustrated Lewis pair (FLP). In the past 16years, the field of enantioselective catalysis by chiral FLPs has been slowly growing. It was shown that chiral LAs are significant as they are involved in the hydrogen transfer (HT) step to the imine, resulting in enantioselectivity. After H2 activation, the borohydride can exist in a number of plausible conformations and their stability is governed by the presence of noncovalent interaction through C-H····π and π····π interactions. However, LBs are not ideal for asymmetric induction as they compete with the imine substrate as a counter LB. Further, the proton transfer from chiral LB to the imine does not induce any chirality as chirality develops in the HT step. However, intramolecular FLPs with chiral scaffold are very efficient as they possess an optimum distance between LA and LB, which facilitates the H2 activation but precludes the adduct formation of the small molecules substrate with the LA component. This mini-review summarizes computational investigation involving chiral LA and LB, and discusses intramolecular FLPs in the enantioselective catalysis.