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The effects of Lewis basicity and acidity on σ-hole interactions were investigated using two sets of carbon-containing complexes. In Set I, the effect of Lewis basicity was studied by substituting the X 3 /X atom(s) of the NC-C 6 H 2 -X 3 and NCX Lewis bases (LB) with F, Cl, Br, or I. In Set II, the W-C-F 3 and F-C-X 3 (where X and W = F, Cl, Br, and I) molecules were utilized as Lewis acid (LA) centers. Concerning the Lewis basicity effect, higher negative interaction energies ( E int ) were observed for the F-C-F 3 ∙∙∙NC-C 6 H 2 -X 3 complexes compared with the F-C-F 3 ∙∙∙NCX analogs. Moreover, significant E int was recorded for Set I complexes, along with decreasing the electron-withdrawing power of the X 3 /X atom(s). Among Set I complexes, the highest negative E int was ascribed to the F-C-F 3 ∙∙∙NC-C 6 H 2 -I 3 complex with a value of -1.23 kcal/mol. For Set II complexes, E int values of F-C-X 3 bearing complexes were noted within the -1.05 to -2.08 kcal/mol scope, while they ranged from -0.82 to -1.20 kcal/mol for the W-C-F 3 analogs. However, V s,max quantities exhibited higher values in the case of W-C-F 3 molecules compared with F-C-X 3 ; preferable negative E int were ascribed to the F-C-X 3 bearing complexes. These findings were delineated as a consequence of the promoted contributions of the X 3 substituents. Dispersion forces ( E disp ) were identified as the dominant forces for these interactions. The obtained results provide a foundation for fields such as crystal engineering and supramolecular chemistry studies that focus on understanding the characteristics of carbon-bearing complexes.

Solid bases are valuable catalysts for industrial syntheses. However, controlling the basicity of these catalysts remains a challenge. Ga4B2O9, due to μ3-O within its structure, could behave as a special solid base catalyst exhibiting intrinsic Lewis basicity. In this work, a sol–gel method was proposed to obtain continuously adjustable acidity and basicity of the metal borate catalyst (AlxGa1−x)4B2O9. According to the results of NH3-TPD, CO2-TPD, and the systematic experimental design, Lewis basic sites originating from GaO5 groups in (AlxGa1−x)4B2O9 boost the Strecker reaction rather than the Lewis acid sites related to unsaturated Al. This work illustrates the possible application of bulk-type solid solutions with simultaneous Lewis acid and base sites for the first time. A reaction mechanism has also been proposed based on the catalytic reaction results. [ABSTRACT FROM AUTHOR]

The reduction of CO and CO 2 by hydrogen to form formaldehyde and methanoic acid is a common way for renewable resources. In the recent decade, Frustrated Lewis Pairs provides a synergetic reaction based on the cooperative Lewis acidity and Lewis basicity to capture small molecules, such as H 2 , CO and CO 2. Generally, the energy barrier is used as the only way to evaluate the performance of different catalyst, lacking a common rule to connect the structure of catalyst and the corresponding properties. However, CO/CO 2 is polarized as the Lewis pairs by Frustrated Lewis Pairs in the activation, the degradation can be viewed as the hydrogenation of activated CO/CO 2. Herein, we learn three classic Frustrated Lewis Pairs composed by Pier's acid and different N-heterocyclic groups to understand the Lewis acidy and basicity in capture of CO and CO 2. By comparing the hydrogenation ability of pristine Frustrated Lewis Pairs and activated CO/CO 2 , the hydrogenation model based on the Lewis acidity or basicity, including the pristine Frustrated Lewis Pairs and the activated CO/CO 2 , can be a common rule to clarify the performances of the degradation of CO/CO 2. [Display omitted] • Establish the hydrogenation model to evaluate the CO/CO 2 degradation efficiency. • CO/CO 2 absorption can be improved by enhanced basicity/acidity of Lewis pairs. • Strong acidity of Lewis pairs catalyst benefits the degradation of CO. • Hydrogenation of CO 2 is determined by stability and basicity of absorbed CO 2. [ABSTRACT FROM AUTHOR]

The introduction of allyl fluorides as alternative electrophiles in asymmetric allylic alkylation reactions has recently attracted significant interest. Despite the intrinsic thermodynamically demanding C–F bond-cleavage event, the fluorophilic nature of the silicon atom is key in assisting the activation and cleavage of the allylic C–F bond. Thus, the use of silylated compounds as unconventional nucleophiles, together with the Lewis basicity of fluorine when acting as a leaving group, enables the development of innovative chemical transformations within mild and selective catalytic schemes. This Synpacts article summarizes the diverse defluorinative asymmetric allylic alkylations with allyl fluorides reported to date under both chiral Lewis base and transition-metal catalysis. [ABSTRACT FROM AUTHOR]

The design of pyridine‐derived organocatalysts aims at the increase of their Lewis basicity, however such an approach is not always efficient. For example, strongly Lewis basic DMAP is completely inefficient as catalyst in the cyclopropanation reaction. Herein we disclose an alternative approach that relies on attenuation of DMAP Lewis basicity. Specifically, the replacement of 4‐dimethylamino substituent in DMAP for 4‐MeO group delivered a highly efficient catalyst for cyclopropanation of electron‐deficient olefins with α‐bromoketones. Kinetic studies provide compelling evidence that the superior catalytic efficiency of 4‐MeO pyridine (MOPY) is to be attributed to the favorable balance between Lewis basicity and leaving group ability. The use of chiral, enantiomerically pure MOPY catalyst has helped to achieve high enantioselectivities (up to 91 : 9 er) in the previously unreported pyridine‐catalyzed cyclopropanation reaction. [ABSTRACT FROM AUTHOR]

We have quantum chemically investigated the boron‐boron bonds in B2, diborynes B2L2, and diborenes B2H2L2 (L=none, OH2, NH3) using dispersion‐corrected relativistic density functional theory at ZORA‐BLYP‐D3(BJ)/TZ2P. B2 has effectively a single B−B bond provided by two half π bonds, whereas B2H2 has effectively a double B=B bond provided by two half π bonds and one σ 2p–2p bond. This different electronic structure causes B2 and B2H2 to react differently to the addition of ligands. Thus, in B2L2, electron‐donating ligands shorten and strengthen the boron‐boron bond whereas, in B2H2L2, they lengthen and weaken the boron‐boron bond. The aforementioned variations in boron‐boron bond length and strength become more pronounced as the Lewis basicity of the ligands L increases. [ABSTRACT FROM AUTHOR]

Designing chiral ligands with an axial symmetry higher than C2‐rotational symmetry is one of the most crucial approaches to improving enantioselectivity in asymmetric synthesis. Herein, C3‐symmetric chiral cage‐shaped phosphites are reported. Their Lewis basicity and chiral environment are precisely controlled by the tethered group. The cage‐shaped phosphites successfully worked as chiral ligands in Rh‐catalyzed asymmetric conjugate additions, realizing acceptable yields with excellent enantioselectivity, and were used to synthesize a pharmacologically important molecule. [ABSTRACT FROM AUTHOR]

Boron‐boron multiple bonds, such as those found in diborenes and diborynes, are typically stabilized by σ‐donor ligands that furnish electron density to these otherwise electron‐deficient species. These compounds are not only of fundamental importance in the study of chemical bonding, but can also activate small molecules in a chemistry reminiscent of that carried out by transition metals. In the pursuit of designing new and improved σ‐donor ligands to stabilize diborenes and diborynes suitable to activate small molecules, we performed density functional calculations to evaluate the Lewis basicity of a series of σ‐donor ligands. For this evaluation, we analysed the interaction between the boranes and the σ‐donor ligands in model systems L→BX3 (X=F and Me) using energy decomposition analyses. We found that electronic bond energies of the L→BX3 adducts correlate well with the ionization energies of the ligands and that ligands with high or medium basicity stabilize diborynes better than ligands with low basicity. We also learnt that beryllium‐based ligands are promising since they are able to stabilize L→B≡B←L diborynes without significantly reducing the triple bond character of the B≡B bond. [ABSTRACT FROM AUTHOR]

Starting with diboranes with two electron‐rich bridging bicyclic guanidinate substituents, we report in this work the rational synthesis of new dicationic symmetrically‐ and unsymmetrically‐substituted diboranes in SN1‐type substitution reactions in which triflato or bromo substituents are replaced by neutral Lewis bases. The scope of such substitution reactions and their rate are analyzed with different pyridine derivatives of variable Lewis basicity. The first substitution step, leading to a monocationic diborane with one anionic substituent (triflate or bromide) and one neutral Lewis base, proceeds much faster than the second substitution step leading to a dicationic diborane with two neutral Lewis bases. The different time scales for the substitution steps could be used to conveniently synthesize in one‐pot reactions several dicationic, unsymmetrically‐substituted diboranes with two different neutral Lewis bases. [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]

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]

• The natural sunlight was used to reduce the composite of graphene oxide and carbon nitride, and for creating Lewis active sites. • The first time use of analytical and electrochemical CO 2 adsorption/stripping studies to investigate the effect of Lewis active sites. • Post CO 2 stripping electrochemical studies to corelate active site performance in terms of electrochemical active surface area (ECSA), active site density (ASD), turn over frequency (TOF) and mass activity (MA). • DFT study results highlighting the catalyst's structure and its impact on lowering the overpotential for ORR. Developing cost-effective and highly active oxygen reduction reaction (ORR) electrocatalysts is crucial for advancing fuel cell (FC) technology, but current efforts face challenges due to high cost and complex synthesis procedures. This study presents a rapid and cost-effective synthesis method utilizing solar radiation to prepare ORR electrocatalysts. The approach involves reducing a composite of 2-dimensional graphene oxide (GO) and porous graphitic carbon nitride (g-C 3 N 4) under solar radiation. This process creates Lewis base centers and a hierarchal porous structure with a high surface area, facilitating O 2 molecule diffusion and adsorption. The resulting electrocatalyst exhibits an onset potential of 0.85 V, follows a four-electron pathway for ORR, and demonstrates excellent methanol tolerance and stability compared to Pt/C. The catalyst's outstanding performance is attributed to abundant Lewis base active centers from g-C 3 N 4 on solar reduced GO (SRGO) sheets, optimized surface area, porosity, and a strong interface between electroactive Lewis centers and conductive graphitic domains. Density functional theory (DFT) results confirm the lower limiting potential of the Pyridinic N site, supporting ORR activity. This novel strategy, using sunlight as synthesis route, provides insights into structural properties, Lewis basicity, and enhanced electrochemical activity of high-performance N-doped carbon ORR catalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

According to a first view on the geometrical and electronic structure of the tris(pentafluoroethyl)silanide, this anion appears as a Lewis base. Quantum chemical calculations on perfluoroalkylated silanides show significantly lower HOMO and LUMO energy levels in comparison to their non‐fluorinated counterparts, which implies reduced Lewis basicity and increased Lewis acidity of the [Si(C2F5)3]− ion. With these findings and a HOMO–LUMO gap of 4.80 eV similar to N‐heterocyclic silylenes (NHSis), perfluoroalkyl silanides are predestined to exhibit Lewis‐amphoteric character similar to silylenes. Deprotonation of Si(C2F5)3H with sterically demanding phosphazene bases afforded thermally stable phosphazenium salts of the [Si(C2F5)3]− anion, which add to benzaldehyde, benzophenone, CS2, and CO2 in various manners. This behavior also mirrors the reactivity of silylenes towards ketones as well as heterocumulenes and is rationalized by Lewis amphotericity being inherent in these silanides. [ABSTRACT FROM AUTHOR]

According to a first view on the geometrical and electronic structure of the tris(pentafluoroethyl)silanide, this anion appears as a Lewis base. Quantum chemical calculations on perfluoroalkylated silanides show significantly lower HOMO and LUMO energy levels in comparison to their non‐fluorinated counterparts, which implies reduced Lewis basicity and increased Lewis acidity of the [Si(C2F5)3]− ion. With these findings and a HOMO–LUMO gap of 4.80 eV similar to N‐heterocyclic silylenes (NHSis), perfluoroalkyl silanides are predestined to exhibit Lewis‐amphoteric character similar to silylenes. Deprotonation of Si(C2F5)3H with sterically demanding phosphazene bases afforded thermally stable phosphazenium salts of the [Si(C2F5)3]− anion, which add to benzaldehyde, benzophenone, CS2, and CO2 in various manners. This behavior also mirrors the reactivity of silylenes towards ketones as well as heterocumulenes and is rationalized by Lewis amphotericity being inherent in these silanides. [ABSTRACT FROM AUTHOR]

In this frontier article some peculiar characteristics of Zn(salen)-type Schiff-base complexes are reviewed. The paper is mainly focused on the most recent and relevant achievements on responsive supramolecular nanostructures and sensing properties, both of them related to the Lewis acidic character of the ZnII centre in these molecular species, providing an interpretation of these features. The sensing properties of Zn(salen)-type complexes mainly originate from optical spectroscopic changes associated with the formation of the adducts upon addition of a Lewis base (analyte), either by deaggregation of dimeric species or displacement of the solvent coordinated to the metal centre. In both cases the direct sensing is related either to the Lewis acidic character of the complex as well as to the Lewis basicity of the analyte. The formation of responsive nanostructures with fluorescent, and/or vapochromic, mechanochromic, and thermochromic characteristics is driven by non-mutual intermolecular Zn⋯O interactions, further stabilized by π–π stacking interactions and/or interdigitation of the alkyl side groups. The Lewis acidic character is not a prerogative of Zn(salen)-type complexes of tetradentate Schiff-bases. Many other classes of ZnII complexes can possess this property. A correct interpretation of their chemistry is certainly useful for further development of these classical coordination compounds as new molecular materials. [ABSTRACT FROM AUTHOR]

Electrochemical N2 reduction provides a promising alternative to the Haber–Bosch process for sustainable ammonia production but enhancing its selectivity and activity remains a significant challenge. Here, this issue is tackled by triggering strong Lewis basicity within the catalyst, which boosts ambient ammonia synthesis from both thermodynamic and dynamic viewpoints. The enhanced π back donation induced by the Lewis base as the electron donor is first confirmed by first‐principle calculations, which greatly activates the NN bond and promotes its dissociation. Moreover, as suggested by molecular dynamics simulations, such abundant Lewis base would contribute to more surface heterogeneity and thus enhanced van der Waals interactions between nitrogen and the catalyst. Localized high concentration of N2 molecules can be realized at the catalyst surface, enabling efficient N2 delivery with a high flux and benefiting the following reaction process. As expected, the proof‐of‐concept metal‐free catalyst achieves a Faradaic efficiency of 62.9% and ammonia yield rate of 41.1 µg h−1 mg−1 at −0.2 V versus reversible hydrogen electrode. With this Lewis base‐assisted strategy, the superior efficiency would greatly reduce the energy loss of the system and cut down the fundamental cost, thus contributing to future practical applications. [ABSTRACT FROM AUTHOR]

In this contribution, the synthesis and the unusual aggregation/deaggregation properties in solution of two dinuclear ZnII Schiff-base complexes of tetradentate Schiff-base units, having non-conjugated spacers between each molecular unit, are reported in comparison to the mononuclear model complex. Through detailed 1H NMR, DOSY NMR, optical absorption, fluorescence emission, and multivariate analysis of optical absorption data, emerge some interesting findings. In solution of non-coordinating solvents, these Lewis acidic species are characterized as monomers stabilized by formation of intramolecular aggregates, having distinct spectroscopic properties in comparison to intermolecular aggregates derived from the mononuclear model analogue. Instead, in coordinating solvents they exhibit a typical behaviour, with formation of stable adducts showing a strong fluorescence. Deaggregation studies using pyridine as reference Lewis base allowed establishing a larger thermodynamic stability of these intramolecular aggregates, in comparison to intermolecular aggregates, even larger than that of aggregates of conjugated multinuclear complexes. The combined analysis of spectroscopic data upon deaggregation with ditopic Lewis bases unambiguously demonstrated the formation of stable 1 : 1 adducts, with higher binding constants in comparison to those related to monotopic species. Therefore, the present Lewis acidic, dinuclear complexes behave as molecular tweezers of ditopic guests having a strong Lewis basicity. [ABSTRACT FROM AUTHOR]

The globally increasing demands for polymer materials stimulate the significantly intense attention focused on the Lewis pair polymerization (LPP) of various polar vinyl monomers catalyzed by Lewis pairs (LPs) composed of Lewis acid (LA) and Lewis base (LB). According to the degree of interaction between LA and LB, LPs could be divided into classical Lewis adduct (CLA), interacting Lewis pair (ILP) and frustrated Lewis pair (FLP). Regulation of the Lewis basicity, Lewis acidity, and steric effects of these LPs has a significant impact on the polymer chain initiation, propagation and termination as well as chain transfer reaction during polymerization. Compared with other polymerization strategies, LPP has shown several unique advantages towards the polymerization of polar vinyl monomers such as high activity, control or livingness, mild conditions, and complete chemo- or regioselectivity. We will comprehensively review the recent advances achieved in the LPP of polar vinyl monomers according to the classification of the employed LPs based on different LAs, by highlighting the key polymerization results, polymerization mechanisms as well as the currently unmet challenges and the future research directions of LPP chemistry. [ABSTRACT FROM AUTHOR]

Selective N moieties in N-doped carbon catalysts were successfully controlled by a room temperature plasma process, where its ORR catalytic activity was found to be related to Lewis Basicity of catalysts. • Tailored 4 types of nitrogen bonding states in N-doped carbon by plasma synthesis. • Correlated the Lewis basicity of N-doped carbon catatlysts to their ORR activities. • Amino-N showed the superior Lewis basicity and ORR activity. The ORR electrocatalytic activity of nitrogen-doped carbon (N-doped carbon) is highly related to the type of nitrogen bondings, which is originated to the charge transfer between carbon and nitrogen. Based on Lewis theory of acid-base reactions, N-doped carbon can be defined as a Lewis base catalyst. The lone pair of electrons on the nitrogen atom mainly contributed to its reactivity, or in other terms, Lewis basicity. Herein, we fabricated selective amino-N, pyrrolic-N, nitrile-N, and oxide-N in N-doped carbon systematically, as well as compared their electrocatalytic activities and Lewis basicities for the first time. Based on the molecular structure of four starting precursors, aniline (C 6 H 5 NH 2), pyrrole (C 4 H 5 N), benzonitrile (C 5 H 7 N), and nitrobenzene (C 6 H 5 NO 2) were successfully formed as selective amino-N, pyrrolic-N, nitrile-N and oxide-N, respectively, via a room temperature plasma synthesis process. From the electrochemical performance, N-doped carbon catalyst with highly selective amino-N demonstrated comparatively higher ORR activity in terms of ORR onset potential and current density. Also, we confirmed the correlation between the ORR activity and Lewis basicity of various N moieties. Based on the electronic structural properties, amino-N with the most superior ORR activity also exhibited the highest basic strength among the studied C N bonding structure. This study provided the relationship among the structural properties, Lewis basicity, and electrocatalytic activity of selective N-doped carbon. [ABSTRACT FROM AUTHOR]

This study investigated the chalcogen bond from an electrostatic perspective using Point-of-Charge (PoC) approach. Two molecular models –namely CX2 and H2X, where X = O, S, and Se– were studied. 2D stabilization energy surfaces were generated for all studied molecules. Moreover, Chal···PoC distance, A-Chal···PoC angle (θ) and solvent effects on chalcogen bond strength were investigated. Natural bond orbital (NBO) calculations were also performed for all studied molecules. Results found that chalcogen bond strength increased with increasing Lewis basicity (i.e., PoC negativity), with closing A-Chal···PoC angle (θ) to 180°, and with increasing chalcogen atomic size in the order O < S < Se. Polarization of the negative PoC on the σ-hole size was revealed. Aqueous medium contributions to molecular stabilization resulted from: (i) the favorable solvent contribution to the positive σ-hole, and (ii) the unfavorable solvent contribution to the negative electrostatic regions of the molecules. σ-node phenomenon was also investigated and explained in the chalcogen-containing molecules. It could thus be concluded that the chalcogen bond is electrostatic and a sum of (i) attractive electrostatic interaction between the σ-hole of chalcogen atom and the Lewis base, and (ii) repulsive electrostatic interaction between the negative belt of chalcogen atom and the Lewis base. [ABSTRACT FROM AUTHOR]

An acid, HI promoted di‐deiodination process for the synthesis of α‐acetoxy/hydroxymethyl ketones from α′‐acetoxy‐α,α‐dihaloketones has been reported. The process is very general in terms of structural diversity of both tertiary‐ as well as secondary‐acetoxy possessing diiodoketones and found to be very efficient. The proposed mechanism involves as initial carbonyl activation by proton (acid) followed by the deiodination by Lewis base (iodide or water), for both the deiodination reactions. By extending this idea of acid activation during deiodination, further we have also developed a cascade conversion of propargylic acetates to corresponding α‐acetoxy/hydroxymethyl ketones under metal free conditions. This strategy is unique and high yielding for total four functional group transformations, i. e. propargylic acetate to diiodoketone to mono‐idodoketone to acetoxymethyl ketone to hydroxymethyl ketone. HI promoted di‐deiodination of α′‐acetoxy‐α,α‐dihaloketones has been developed for the synthesis of α‐acetoxy/hydroxymethyl ketones. The proposed mechanism involves two sequential deiodination reactions via an initial carbonyl activation by acid followed by deiodination by Lewis base. We have also developed a cascade conversion of propargylic acetates to α‐acetoxy/hydroxymethyl ketones under metal free conditions. This strategy is unique and involves total of four functional group transformations, i. e. propargylic acetate to diiodoketone to mono‐idodoketone to acetoxymethyl ketone to hydroxymethyl ketone. [ABSTRACT FROM AUTHOR]

Butanone is a toxic, flammable and explosive volatile gas, and the rapid detection of butanone can help avoid safety accidents and protect human lives. However, the detection of butanone remains difficult to meet the practical requirements. Inappropriate resistance and insufficient reactivity are challenges for butanone sensing materials. Constructing amorphous and crystalline heterojunctions and modulating the electronic structure of the heterojunction interface promise to coordinate the resistance and reactive sites. In this work, the cubic heterostructure of crystalline ZnO/amorphous ZnSnO 3 was constructed and oxygen vacancies and Lewis acid base were regulated by In atoms. 5 wt% In-ZnO/ZSO response for 100 ppm butanone was 166.7 at 280 °C, 7.1 times higher than ZnO/ZSO, with 20 ppb detection limit and 1.5 s response time. The excellent butanone response attributes to electronic structure modulation in the amorphous heterojunction by In atom. The oxygen vacancies increase the Lewis basicity of the metal atoms and enhance the butanone response. • Construction of ZnO/ZSO cubic heterojunction with high In atom doping content. • In atom doping modulates the oxygen vacancies in ZnO/ZSO heterogeneous. • Oxygen vacancy enhanced Lewis bases contribute to the butanone response. • The sensor response167 to 100 ppm butanone with 20 ppb limit detection. [ABSTRACT FROM AUTHOR]

The structures of the covalent Lewis adducts and/or frustrated Lewis pairs derived from 2- and 2,6-substituted pyridines with diaryl (Ar2CH+) and with the more bulky triaryl (Ar3C+) carbenium ions were analyzed by UV-vis and NMR spectroscopy. Thermodynamics (equilibrium constants) and kinetics (rate constants) of the associations of the carbon-centered Lewis acids Ar2CH+ with a series of sterically hindered pyridines were investigated and used for the determination of the Lewis basicities and nucleophilicities, on the basis of the Mayr electrophilicity/nucleophilicity and Lewis acidity/basicity linear free energy relationships. In addition, methyl and benzhydryl cation affinities were computed to elucidate the respective steric and electronic contributions of the substituents to the nitrogen atom Lewis basicity. The influence of the size of the reference carbenium ion on the magnitude of the repulsion induced by the pyridine substituents (Me, tBu in 2- or 2,6-positions) was also analyzed. Cumulated steric repulsion was found to decrease the reactivity of the nitrogen atom by up to 10 orders of magnitude. [ABSTRACT FROM AUTHOR]

The nucleophilicity and Lewis basicity of sterically hindered phosphines, widely used in catalysis and in frustrated Lewis pair (FLP) chemistry, have been quantified by determining the rates and equilibrium constants of their associations with reference systems (benzhydrylium and tritylium ions) of calibrated electrophilicities and Lewis acidities. These structure-reactivity investigations allow a rationalization of the Lewis acid-base interactions all along the way from covalent Lewis adducts to FLPs. Comparisons of the association of phosphines of increasing sizes (Ph3P, ( o-tolyl)3P, and tBu3P) with the triarylborane B(C6F5)3 and with the isoelectronic tritylium ions Ar3C+ provide detailed insights for the future fine-tuning of the reactivities of FLPs. As a proof of concept, tritylium-ion-derived FLPs were shown to react with alkynes, as reported for the FLPs derived from the benchmark triarylborane B(C6F5)3. [ABSTRACT FROM AUTHOR]

• Lewis basicity is an essential property of molecules used as electrolytes and additives. • The Gutmann Donor Number of alkyl carbonates shows shortcomings. • The enthalpy of adduct formation with boron trifluoride is a reliable measure of Lewis basicity. • Experimental data and ab initio calculation can be used as an alternative to Donor Number. Alkyl carbonates are essential components in the manufacture of lithium-ion batteries, as electrolytes or additives. The Lewis basicity of alkyl carbonates and other carbonyl compounds used in electrochemistry are often characterized by their Donor Number (DN). Assessment of the literature DN values displays great discrepancies. This is attributed in part to experimental errors, but mostly to inconsistent methods of determination. An alternative Lewis basicity scale is proposed, based on the enthalpy of adduct formation of a Lewis base with BF 3 in dichloromethane solvent -Δ H (BF 3). Experimental data are well reproduced by a modified ab initio G4 method and a mixed cluster-continuum approach of solvation. These calculations permit a confident estimation of previously not measured -Δ H (BF 3) values. The combination of a large set of experimental data and of calculations provides a consistent source of Lewis basicity of molecules used in electrochemistry and related fields. [ABSTRACT FROM AUTHOR]

A highly facile and efficient electrophilic bromolactonization of cyclopropylcarboxylic acids could be effected by a Lewis basic sulfide catalyst. Mechanistic studies performed revealed that the cyclopropane substrates could undergo radical bromination upon exposure to light, yielding a mixture of regioisomers. In stark contrast, the Lewis basic sulfide catalyst could promote the electrophilic bromolactonization and yield the Markovnikov product exclusively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Global nucleophilicity index (N) as a metric of Lewis basicity. • Nucleophilicity and vertical ionization energy are in an inverse relationship. • Superalkali ligands increase the nucleophilicity of Lewis bases. • nc-2e (n = 1,2) gives the bonding nature of design Lewis bases. • Charge transfer descriptor confirms the formation of Lewis acid-base adducts. Inquest for efficient Lewis base an in-silico investigation on NH 3 and its structurally similar molecules has been carried out. It has been observed that the ionization energy of the groups attached to the N -centre plays a vital role in determining their stability and reactivity. Among different groups, superalkali ligands make a better Lewis base. Several conceptual DFT descriptors like electrophilicity, nucleophilicity, dual descriptors have been used to analyse the stability and reactivity of the proposed Lewis base. The calculated charge transfer descriptor describes the efficiency of the designed Lewis base to form an adduct with Lewis acid. nc-2e (n = 1,2) AdNDP calculation lends additional support to the bonding of the studied molecules. [ABSTRACT FROM AUTHOR]

1,3-Dimethyldisiloxane, O(SiH2Me)2, diethyl ether, OEt2, and their metal complexes (Li+,Ag+) have been used as model systems to uncover the reasons underlying the lower Lewis basicity of siloxanes compared to analogous ethers. Bonding in the metal complexes has been analyzed with quantum theory of atoms in molecules as well as natural bond orbital theory. The binding to Li+ by O(SiH2Me)2 and OEt2 is largely of monopole - dipole type whereas binding of Ag+ also shows small charge transfer components. The more ionic Si-O bonds in O(SiH2Me)2 compared to C-O bonds in OEt2 lead to more negative charge on the oxygen atom of O(SiH2Me)2 but the electrostatic attraction between metal cations and OEt2 is calculated to be slightly stronger by interacting quantum atoms energy decomposition analysis. The lower electrostatic attraction by O(SiH2Me)2 is due to repulsion between positively charged silicon atoms and the metal cations that compensate for the stronger attraction from the oxygen atom relative to OEt2. The total interaction of metal cations with O(SiH2Me)2 was calculated to be almost as strong as that with OEt2 and the lower stability of O(SiH2Me)2 complexes and the lower Lewis basicity of O(SiH2Me)2 is attributed to changes in the bonding and polarization of the ligands in the presence of metal cations. The polarization of O-Si bonds in O(SiH2Me)2 raises the energy of the molecule more than does the polarization O-C bonds in OEt2. Despite the lower stability of O(SiH2Me)2 metal complexes, solid state reaction enthalpies arising from a volume-based thermodynamics approach suggest that they could be stabilized with a sufficiently large anion such as [Al(ORF)4]-. [ABSTRACT FROM AUTHOR]

The Lewis basicity of selected organic bases, modeled by the enthalpies of adduct formation between gaseous BF3 and bases in dichloromethane (DCM) solution, is critically examined. Although experimental enthalpies for a large number of molecules have been reported in the literature, it may be desirable to estimate missing or uncertain data for important Lewis bases. We decided to use high-level ab initio procedures, combined with a polarized continuum solvation model, in which the solvated species were the clusters formed by specific hydrogen bonding of DCM with the Lewis base and the Lewis base/BF3 adduct. This mode of interaction with DCM corresponds to a specific solvation model (SSM). The results essentially showed that the enthalpy of BF3 adduct formation in DCM solution was clearly influenced by specific interactions, with DCM acting as hydrogen-bonding donor (HBD) molecule in two ways: base/DCM and adduct/DCM, confirming that specific solvation is an important contribution to experimentally determined Lewis basicity scales. This analysis allowed us to conclude that there are reasons to suspect some gas-phase values to be in error by more than the stated experimental uncertainty. Some experimental values in DCM solution that were uncertain for identified reasons could be complemented by the computed values. [ABSTRACT FROM AUTHOR]

[Display omitted] • Phosphate modified octahedral CeO 2 {111} surface with g-C 3 N 4 were synthesized. • PO 4 3− modification improved more Lewis base sites for CO 2 adsorption/activation. • PO 4 3− acted as interfacial bridge for built-in electric field and Z-scheme formation. • P-CeO 2 /g-C 3 N 4 had excellent activity for fast charge transfer and rich active sites. For photocatalytic CO 2 reduction, directional charge-transfer channel and abundant active sites are of significance. Herein, we designed and fabricated phosphate modified octahedral CeO 2 {111} surface coupling with g-C 3 N 4 (P-CeO 2 /g-C 3 N 4) for photocatalytic CO 2 reduction, which had superior activity than others, i.e., P-CeO 2 , g-C 3 N 4 , CeO 2 /g-C 3 N 4. The characterization results revealed the coordination environment of P species, as well as, the presence of hydrogen bond between phosphate and amino. Through the PO 4 3− bridge, the interfacial electrons donated from g-C 3 N 4 to CeO 2 , leading to the Z-scheme formation and fast photo-generated charge transfer. Furthermore, PO 4 3− modification increased more oxygen-containing functional groups on surface, which acted as Lewis basic sites for CO 2 reactant adsorption and activation. Therefore, under the synergistic interaction of charge-transfer channel and abundant active sites, P-CeO 2 /g-C 3 N 4 is a potential photocatalyst for CO 2 reduction. [ABSTRACT FROM AUTHOR]

[Display omitted] • The halogen bonding between C 4 F 9 I and a series of Lewis bases was investigated. • UV–Visible and Raman experiments combined with DFT calculations are reported. • Halogen bonding interaction, Lewis basicity and UV–visible spectra are correlated. • Light induced perfluoroalkylation reactions activated by halogen bonding are discussed. Visible light promoted perfluoroalkylation reactions initiated via halogen bonding interactions between perfluoroalkyl iodides (Rf–I, Rf = C n F 2n+1) and Lewis bases have been recognized as a powerful tool in the field of radical synthetic chemistry. In order to provide some insights into the nature, strength and role in the activation process of halogen bonding interactions, we have performed a combined UV–Visible/Raman/DFT study on a model Rf–I (C 4 F 9 I) and a series of Lewis bases (LB) frequently used for the activation of perfluoroalkylation reactions, including DBU, MTBD, TMG, TMEDA and Et 3 N. Raman studies conducted in acetonitrile solutions show that the band at 279 cm−1 associated with the C I stretching normal mode of C 4 F 9 I shifts about 20 cm−1 towards lower wavenumbers upon formation of the halogen-bonded complexes. Additionally, the Raman study revealed that at concentrations typically used for perfluoroalkylation reactions, the [C 4 F 9 I-LB] complexes are the main species present in solution. UV–Vis spectroscopy revealed that complex formation is characterized by a strong increase in absorption from 225 to 350 nm. The higher the basicity of the Lewis base, the higher the increase of the UV absorbance. [ABSTRACT FROM AUTHOR]

• Lewis base HMPA having a high donor number was added to the one-step process of MAPbI 3. • HMPA promoted pinhole-free perovskite films by forming PbI 2 -HMPA adducts. • Adducts controlled nucleation and growth rates to form homogeneous perovskite. • The exact 3D locations of residual PbI 2 acting as a passivation layer are characterized. • Power conversion efficiency of solar cells was enhanced from 15.73% to 17.09%. To fabricate efficient MAPbI 3 perovskites using the Lewis acid-base adduct approach, we used a Lewis base hexamethylphosphoramide (HMPA) having a high donor number (D N), and investigated the effect of high-D N HMPA treatment on the properties of planar MAPbI 3 -based solar cells. The main functions of the HMPA treatment were to passivate the perovskites by forming well-distributed PbI 2 phases and to densify the perovskites by controlling the rate constants. The treatment with Lewis base HMPA by one-step spin coating and subsequent solvent washing promoted the formation of pinhole-free perovskite films by increasing the coordination ability of HMPA with Pb2+ adducts and controlling the nucleation and growth rates of the perovskites. In addition, treatment with various concentrations of HMPA led to the formation of a residual PbI 2 phase that acted as a passivation layer, even though stoichiometric quantities of precursors were used. Through a series of advanced electron microscopy studies, the exact three-dimensional locations of the PbI 2 passivation layers were determined. Furthermore, by calculating the decreased active trap concentrations and carrier densities, we verified the passivation effect of remnant PbI 2. Importantly, we achieved the best power conversion efficiency of 17.09% by the controlled addition of Lewis base HMPA, thus demonstrating a much improved performance than that obtained without HMPA treatment (15.73%). [ABSTRACT FROM AUTHOR]

The zinc(II) ion forms stable complexes with a wide variety of ligands, but those related to Schiff-bases are among the most largely investigated. This review deals with the peculiar aggregation characteristics of Zn(II) Schiff-base complexes from tetradentate N2O2 salen-type ligands, L, derivatives from salicylaldehydes and 1,2-diamines, and is mostly focused on their spectroscopic properties in solution. Thanks to their Lewis acidic character, ZnL complexes show interesting structural, nanostructural, and aggregation/deaggregation properties in relation to the absence/presence of a Lewis base. Deaggregation of these complexes is accompanied by relevant changes of their spectroscopic properties that can appropriately be exploited for sensing Lewis bases. Thus, ZnL complexes have been investigated as chromogenic and fluorogenic chemosensors of charged and neutral Lewis bases, including cell imaging, and have shown to be selective and sensitive to the Lewis basicity of the involved species. From these studies emerges that these popular, Lewis acidic bis(salicylaldiminato)Zn(II) Schiff-base complexes represent classical coordination compounds for modern applications. [ABSTRACT FROM AUTHOR]