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Here in we report Ag(I)-promoted homo-dimerization of 2-(alk-2-yn-1-onyl)-1-alkynylbenzenes for the synthesis of structurally novel and functionalized naphthalene derivatives. This transformation has exhibited a broad scope for the alkyl as well as aryl groups present on alkynes. Observations made from the control experiments, had suggested the possible mechanism as i) homo-dimerization of in situ generated benzopyrylium ion intermediates through a head–tail [4+2] cycloaddition, followed by ii) the competitive aromative ring-opening vs. decarbonylative aromatization of the adduct to give the formylated and deformylated naphthalenes respectively.

Thiolate adducts of dirhodium(II) tetraacetate have proven difficult to prepare. We isolated a stable, paramagnetic Ni4Rh2 adduct containing Ni-based metallothiolates bound in axial positions of the Rh24+ core. The adduct formation is accompanied by a change of the magnetic exchange interaction in the dinuclear Ni2 subunits.

Mononuclear high-valent iron(IV)-oxo intermediates are excellent oxidants towards oxygenation reactions by heme and nonheme metalloenzymes and their model systems. One of the most important functions of these intermediates in nature is to detoxify various environmental pollutants. Organic substrates such as halogenated phenols are known to be water pollutants which can be degraded to their less hazardous forms through an oxidation reaction by iron(IV)-oxo complexes. Metalloproteins in the Nature utilize various types of second-coordination sphere interactions to anchor the substrate in the vicinity of the active site. This concept of substrate-binding is well-known for natural enzymes, but quite elusive for the relevant biomimetic model systems. Herein, we report the oxidative reactivity patterns of an iron(IV)-oxo intermediate, [FeIV(O)(2PyN2Q)]2+, (2PyN2Q = 1,1-di(pyridin-2yl)-N, N-bis(quinolin-2-ylmethyl)methanamine) with a series of mono-, di- and tri-halophenols. A detailed experimental study shows that the dehalogenation reactions of the halophenols by such iron(IV)-oxo intermediates proceed via an initial hydrogen atom abstraction from the phenolic O-H group. Further, based on the size and nucleophilicity of the halophenol, an intermediate substrate-bound species forms , that is a phenolate adduct to the ferric species - which thereafter leads to the formation of the corresponding products.

Triangular silver(i) and copper(i) 3,5-diethyl-4-nitropyrazolates (abbreviated as [Ag(denpz)]3 or Ag3pz3, and [Cu(denpz)]3 or Cu3pz3), as well as their adducts with dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (DMDBT) and benzothiophene (BT), have been prepared and characterized by a series of techniques. X-ray analyses show that these adducts are stabilized by MS, MC contacts and ππ stacking interactions. NMR measurements and theoretical calculations indicate that the intensity of interaction between the metal complexes and dibenzothiophenes follows the trend: Ag3pz3-DMDBT > Ag3pz3-DBT > Cu3pz3-DMDBT > Cu3pz3-DBT, which can be understood on the basis of a weak interaction between π-acid (Ag3pz3 or Cu3pz3) and π-base (DBT/DMDBT). Both complexes show good adsorptive ability and reusability toward the removal of DBT and DMDBT from model oil (n-octane), with the maximum adsorption capacity at room temperature being 39 mg S (DMDBT) per g Cu3pz3, 34 mg S (DMDBT) per g Ag3pz3, 40 mg S (DBT) per g Cu3pz3, 36 mg S (DBT) per g Ag3pz3, respectively. Compared to Ag3pz3, Cu3pz3 exhibits higher adsorptive capacities for DBT/DMDBT, which has been attributed to its lower molecular mass.

The reaction of [Cp*Ru(μ-NHPh)]2 (Cp* = η5-C5Me5) with Lewis acids of the type MX2 (M = Zn, Sn, Pb; X = Cl, OTf) affords Ru2 → M donor-acceptor adducts characterized as π complexes of a Ru[double bond, length as m-dash]Ru double bond with M(ii) Lewis acids. The results illustrate for the first time the ability of σ-acceptor Lewis acid ligands to induce the formation of a metal-metal multiple bond via stabilizing dative interactions.

The lysozyme binding affinity and the electronic properties of [ReX(CO)3(terpy-κ2N1,N2)] (X = Br− and triazolateCOOCH2CH3,CF3) were reported. The triazolate complex was prepared in a [3 + 2] cycloaddition click reaction. The bromo compound reacted with lysozyme affording adducts with Re(CO)3+ fragments, while the triazolate compound persisted. A red shift of the MLCT band of the triazolate compound in progressively less polar solvents may be due to the negative solvatochromism.

We report the reactivity between the water stable Lewis acidic trioxatriangulenium ion (TOTA+) and a series of Lewis bases such as phosphines and N-heterocyclic carbene (NHC). The nature of the Lewis acid–base interaction was analyzed via variable temperature (VT) NMR spectroscopy, single-crystal X-ray diffraction, UV-visible spectroscopy, and DFT calculations. While small and strongly nucleophilic phosphines, such as PMe3, led to the formation of a Lewis acid–base adduct, frustrated Lewis pairs (FLPs) were observed for sterically hindered bases such as P(tBu)3. The TOTA+–P(tBu)3 FLP was characterized as an encounter complex, and found to promote the heterolytic cleavage of disulfide bonds, formaldehyde fixation, dehydrogenation of 1,4-cyclohexadiene, heterolytic cleavage of the C–Br bonds, and interception of Staudinger reaction intermediates. Moreover, TOTA+ and NHC were found to first undergo single-electron transfer (SET) to form [TOTA]·[NHC]˙+, which was confirmed via electron paramagnetic resonance (EPR) spectroscopy, and subsequently form a [TOTA–NHC]+ adduct or a mixture of products depending the reaction conditions used., Frustration at carbon! Herein, we present a frustrated Lewis pair system derived from a water stable carbon-based Lewis acid, trioxatriangulene (TOTA+), and a variety of Lewis bases, which successfully promotes bond cleavage and molecule fixation.

2,3-Dimethoxy-2,3-dimethyl-1,4-dioxane readily prepared from biacetyl serves as a stable precursor to 2,3-dimethylene-1,4-dioxane which undergoes a [4+2] cycloaddition reaction with dienophiles to give functionalized cyclohexene derivatives. The cycloaddition adducts obtained by the present procedure are transformed into potentially useful intermediates for biologically important materials.

Itaconate is a mammalian antimicrobial metabolite that inhibits the isocitrate lyases (ICLs) of Mycobacterium tuberculosis. Herein, we report that ICLs form a covalent adduct with itaconate through their catalytic cysteine residue. These results reveal atomic details of itaconate inhibition and provide insights into the catalytic mechanism of ICLs.

A formal diastereoselective 1,3-dipolar cycloaddition of azomethine ylide and coumarin derivatives to construct coumarin based spiro multi heterocyclics has been described. The in situ generation of azo-ylide was achieved for various heterocyclic carbonyls (indenoquinoxaline and isatin). This transformation is also suitable for maleimide dipolarophiles for the synthesis of hydro-maleimide derivatives. These decarboxylative annulations neither required any catalyst nor any activator. Further the pure products were isolated by filtration from the reaction mixture after the reaction under ambient conditions.

The increase of CO2 levels is becoming a global problem in the 21st century, leading to current requests for new advanced materials and methods of CO2 utilisation. Here, we propose a hybrid plasmonic catalyst for the transformation of CO2 to carbonates in quantitative yields under ambient conditions, in contrast to the commonly applied elevated temperature and pressure. The proposed catalyst presents a combination of gold nanoparticles modified by triazabicyclodec-5-ene (TBD). TBD is responsible for CO2 fixation, forming a zwitterionic adduct near the plasmonic surface. The terminating stage, namely the interaction of the zwitterionic adduct with the epoxide, is pumped by plasmonic triggering and is the first example of plasmon-assisted CO2 cycloaddition. Taking advantage of the proposed catalyst, we achieved an unprecedented turnover number, turnover frequency, and apparent quantum yield, even in the case of air as a CO2 source and light as an energy input. Control experiments, including variation of illumination conditions and temperature, prove that the photochemical pathway proceeds through plasmon excitation.

Uronic acids are not only important building blocks of polysaccharides and oligosaccharides but also are widely used in the food and pharmaceutical industries. Inspired by the structure of natural products, here, we disclosed base-mediated and radical-mediated hydrothiolation reactions for the preparation of thiol-contained uronates. In comparison with base-mediated reaction, radical-mediated hydrothiolation is inefficient due to the electron-withdrawing group on the ethylene group; nevertheless, the adduct had excellent stereoselectivity at both C-4 and C-5 positions. For the alkaline approach, thiols as nucleophiles can regioselectively and stereoselectively attach to the C-4 position of Δ-4,5-unsaturated uronate with moderate to good yields. However, poor stereoselectivity at the C-5 position was observed due to retro thiol-Michael addition. After removing the protecting group of the thiol, the thiol adduct was isomerized to the furanosidic form and the 4-thiol-furanosidic uronate derivative was synthesized for the first time.

The umpolung Michael addition of isatin N,N′-cyclic azomethine imine 1,3-dipoles with chalcones is reported. The reaction could be finished within a very short time (0.3–2 min), with 3,3-disubstituted oxindole derivatives obtained in moderate to excellent yields with promising dr values. Unusual Michael adducts were obtained in moderate to high yields (26–98%) with low to high diastereoselectivities (0.8 : 1 to 8.5 : 1 dr). All the synthesized compounds (3, 3′, 4, 5, 5′, 7, 7′, 9 and 9′) were well characterized by FTIR, NMR, and mass spectral analyses and further confirmed by the single-crystal X-ray diffraction analysis of compounds 3aa and 4n.

Attempts to investigate the properties and reactivity of the stiboryl moiety (R3Sb+-O- or R3Sb[double bond, length as m-dash]O), as in monomeric stibine oxides free of interaction with Lewis acids/bases, led us to conclude that this functional group remains undiscovered. X-ray crystallographic, computational, and spectroscopic data indicate that previously proposed H-bonded stibine oxide adducts Mes3SbOHO3SR are in fact hydroxystibonium salts [Mes3SbOH][RSO3].

Rate coefficients, k, for the gas-phase Cl + Furan-2,5-dione (C4H2O3, maleic anhydride) reaction were measured over the 15–500 torr (He and N2 bath gas) pressure range at temperatures between 283 and 323 K. Kinetic measurements were performed using pulsed laser photolysis (PLP) to produce Cl atoms and atomic resonance fluorescence (RF) to monitor the Cl atom temporal profile. Complementary relative rate (RR) measurements were performed at 296 K and 620 torr pressure (syn. air) and found to be in good agreement with the absolute measurements. A Troe-type fall-off fit of the temperature and pressure dependence yielded the following rate coefficient parameters: ko(T) = (9.4 ± 0.5) × 10−29 (T/298)−6.3 cm6 molecule−2 s−1, k∞(T) = (3.4 ± 0.5) × 10−11 (T/298)−1.4 cm3 molecule−1 s−1. The formation of a Cl·C4H2O3 adduct intermediate was deduced from the Cl atom temporal profiles and an equilibrium constant, KP(T), for the Cl + C4H2O3 ↔ Cl·C4H2O3 reaction was determined. A third-law analysis yielded ΔH = −15.7 ± 0.4 kcal mol−1 with ΔS = −25.1 cal K−1 mol−1, where ΔS was derived from theoretical calculations at the B3LYP/6-311G(2d,p,d) level. In addition, the rate coefficient for the Cl·C4H2O3 + O2 reaction at 296 K was measured to be (2.83 ± 0.16) × 10−12 cm3 molecule−1 s−1, where the quoted uncertainty is the 2σ fit precision. Stable end-product molar yields of (83 ± 7), (188 ± 10), and (65 ± 10)% were measured for CO, CO2, and HC(O)Cl, respectively, in an air bath gas. An atmospheric degradation mechanism for C4H2O3 is proposed based on the observed product yields and theoretical calculations of ring-opening pathways and activation barrier energies at the CBS-QB3 level of theory.

High-quality large-area perovskite films are realized by an anti-solvent-free adduct approach using 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (DMPU) as a Lewis base additive. Perovskite crystallization kinetics was found to depend on the latent heat of vaporization, associated with vapor pressure, and donor number of the Lewis base under force convection in air-knife-assisted D-bar coating. The conventionally used dimethyl sulfoxide (DMSO) or N-methyl-2-pyrrolidone (NMP) Lewis base is inappropriate for high-quality perovskite films because of rapid co-evaporation with solvents by argon gas blowing generated under 1.5 MPa, while the DMPU-containing precursor solution induces the formation of a stable adduct intermediate in the as-deposited film due to the low vapor pressure and high donor number of DMPU. Upon addition of DMPU into the precursor solution, the concentration of DMPU is found to affect the morphology and photo-excited carrier lifetime of the resulting perovskite film. A piece of the (FAPbI3)0.95(CsPbBr3)0.05 perovskite film coated on a 4.8 × 9.6 cm2-substrate was used for testing the photovoltaic performance, where the power conversion efficiency (PCE) significantly improved from 3.21% to 20.08% (best PCE is 20.56%) when 0.5 M DMPU (with respect to 1 M of perovskite) was added into the precursor solution. A monolithic perovskite solar module with an active area of 19.69 cm2, employing the perovskite film formed from the 0.5 M DMPU-containing solution, demonstrates a PCE of 17.94%.

The current understanding of Lewis acid effects on transition metal catalysis is generally based on the enhanced charge transfer from metal to substrate due to the formation of Lewis acid–base adducts. The critical factors of how Lewis acids manipulate complex catalyst–substrate interactions to facilitate reactions are seldom clarified. Herein, using the energy decomposition approach, we quantify the contributions of multiple factors which account for the Lewis acid acceleration in Ni-catalyzed C–X (X = H, C, O) bond cleavage via oxidative addition. The results reveal that the dominant factors for Lewis acid promotion highly depend on the features of transition states with Lewis acids. In the transition states having only heteroatom–Lewis acid interactions (e.g., C–H, C–CN and C(acyl)–O oxidative additions), the reactivity is improved majorly by enhancing charge transfer from the metal to the Lewis acid-activated substrates, which is consistent with the conventional viewpoint. However, for the transition states with heteroatom–Lewis acid and heteroatom–transition metal interactions (e.g., C(benzyl)–O and C(aryl)–O oxidative additions), the decisive factor for the improved reactivity is ascribed to the reduced Pauli repulsion between occupied orbitals. Further, in the transition states having heteroatom–Lewis acid and Lewis acid–transition metal interactions (e.g., C(benzyl)–O oxidative addition), the reaction is facilitated by strengthening electrostatics and polarization due to greater charge separation and electron delocalization effects. These three types of dominant factors are generally employed by a series of different Lewis acids in promoting Ni-catalyzed bond cleavage.

A simple protocol has been developed for the chemoselective synthesis of ferrocene-containing Rauhut–Currier adducts from 1-ferrocenyl-2-nitroethene and vinyl ketones using 20 mol% of triphenylphosphine. Multifunctional ferrocene derivatives were obtained in moderate to high yields (51–92%) by the coupling between the α-position of vinyl ketones and the β-position of the nitroalkene. The study of the Rauhut–Currier reaction under the described conditions showed that the strong electron-donating group at the β-position of nitroalkenes plays a significant role in the reaction outcome due to prevention of polymerization and stabilization of the zwitterionic intermediate. Additionally, a preparative synthesis of 4-ferrocenyl-3-methylene-5-nitropentan-2-one was carried out and its synthetic transformations showed easy conversion to other useful building blocks. Supplementary material: [https://vinar.vin.bg.ac.rs/handle/123456789/10085] Dataset: [https://vinar.vin.bg.ac.rs/handle/123456789/10086]

Natural systems produce various γ-dicarbonyl-bearing compounds that can covalently modify lysine in protein targets via the classic Paal–Knorr reaction. Among them is a unique class of lipid-derived electrophiles – isoketals that exhibit high chemical reactivity and critical biological functions. However, their target selectivity and profiles in complex proteomes remain unknown. Here we report a Paal–Knorr agent, 4-oxonon-8-ynal (herein termed ONAyne), for surveying the reactivity and selectivity of the γ-dicarbonyl warhead in biological systems. Using an unbiased open-search strategy, we demonstrated the lysine specificity of ONAyne on a proteome-wide scale and characterized six probe-derived modifications, including the initial pyrrole adduct and its oxidative products (i.e., lactam and hydroxylactam adducts), an enlactam adduct from dehydration of hydroxylactam, and two chemotypes formed in the presence of endogenous formaldehyde (i.e., fulvene and aldehyde adducts). Furthermore, combined with quantitative chemoproteomics in a competitive format, ONAyne permitted global, in situ, and site-specific profiling of targeted lysine residues of two specific isomers of isoketals, levuglandin (LG) D2 and E2. The functional analyses reveal that LG-derived adduction drives inhibition of malate dehydrogenase MDH2 and exhibits a crosstalk with two epigenetic marks on histone H2B in macrophages. Our approach should be broadly useful for target profiling of bioactive γ-dicarbonyls in diverse biological contexts., Natural systems produce various γ-dicarbonyl-bearing compounds that can covalently modify lysine in protein targets via the classic Paal–Knorr reaction.

A unique C30 steroid, solitumergosterol A (1), was isolated from the deep-sea-derived fungus Penicillium solitum MCCC 3A00215. The planar structure and relative configuration of 1 were established mainly on the basis of extensive analysis of its 1D and 2D NMR as well as HRESIMS data, while its absolute configuration was clarified by comparison of the experimental and theoretical ECD spectra. Noteworthily, 1 is a Diels–Alder adduct of a heterogeneous steroid bearing a 6/6/6/6/5 pentacyclic carbon skeleton. Solitumergosterol A (1) exhibited weak in vitro anti-tumor activity against MB231 cells by a RXRα-dependent mechanism.

The unexpected Diels-Alder reaction of [60]fullerene (C60) with ferrocenes bearing electron-withdrawing groups as cyclopentadiene surrogates has been developed to selectively afford single isomers of [2 + 4] cycloadducts of C60. Mechanistic studies indicate that cyclopentadienes are in situ generated from electron-deficient ferrocenes in the presence of an oxidant and an acid, followed by [2 + 4] cycloadditions with dienophiles. A Michael addition reaction using a Grignard reagent has been utilized to transform the Diels-Alder adducts of C60 into more stable fullerene derivatives.

2,4-Diamino-6-phenyl-1,3,5-triazine-1-ium nitrate (LH)(NO3) crystallises in the triclinic centrosymmetric space group P with an intriguing high number of crystallographically unique salt-like adducts (Z′ = 8) and a total number of ionic species (Z′′ = 16) in the asymmetric unit. The organic cations and nitrate anions are combined into two similar H-bonded neutral tapes strengthening by 20 unique NH⋯O and NH⋯N hydrogen bonds each. Hydrogen bonds are ordered into a repeated sequence of homo- and hetero-synthons, R22(8)R33(10)R22(8)R22(8)R24(8)R33(10) as ring motifs. The paired cations form R22(8) ring motifs through base pairing of N–H⋯N hydrogen bonds. All other patterns include both cations and anions. In the crystal structure, the compromise between the tapes rigidity provided by the multiple directional H-bonds within the tapes and packing preferences is reached through the restricted internal rotation about the C–C bond joining the phenyl and triazine cycles in the 2,4-diamino-6-phenyl-1,3,5-triazine-1-ium cations. The decisive impact of NH⋯O(N) hydrogen bonds in the crystal stability and distribution of other types of intermolecular interactions was estimated by Hirshfeld surface analysis. The undertaken CSD overview for the metal-free L-based crystals reveals the exclusivity of the title compound from the viewpoint of the high reported Z′/Z′′ values and the number of unique hydrogen bonds.

Chemical compounds with antioxidant behavior are recognized as efficient protectors against the harmful effects of reactive oxygen species (ROS) and other chemicals overproduced due to oxidative stress (O.S.). Sesamol has been shown to offer significant benefits in the treatment of many OS-induced diseases. The present work focuses on the free radical scavenging activity of some sesamol derivatives, recently proposed as promising antioxidants. This activity was studied, taking into account three reaction mechanisms: formal hydrogen atom transfer (f-HAT), single electron transfer (SET), and radical adduct formation (RAF). The investigation was based on thermochemistry and kinetics, using solvent models to mimic aqueous and lipid environments. The influence of pH on the investigated activity was also considered. The studied sesamol derivatives were found to be potent peroxyl radical scavengers, which suggests that they have potential use to mitigate O.S. and related diseases. SET and f-HAT were identified as the main reaction mechanisms, while RAF was ruled out as a significant chemical route. It is expected that the results from this work will promote further investigations on the possible health benefits of the newly designed sesamol derivatives studied here.

9-Aluminafluorenes have only been sparingly investigated and their properties still remain largely unexplored. Herein, we report the synthesis of five aluminafluorene derivatives with a diverse array of aluminium substituents and probe their Lewis acid properties and reactivity. We show that 9-bromo-9-aluminafluorene readily forms Lewis acid-base adducts with N-heterocyclic carbenes (NHCs), cyclic (alkyl)(amino)carbenes (CAACs) and pyridines and that it undergoes a selective ring expansion reaction with the iminoborane tBuN[triple bond, length as m-dash]BMes to give a seven-membered ring, which can be viewed as a boron-nitrogen analogue of alumepins.

Antioxidant and UV absorption activities of three marine product originated - aaptamine derivatives including piperidine[3,2-b]demethyl(oxy)aaptamine (C1), 9-amino-2-ethoxy-8-methoxy-3H-benzo[de][1,6]naphthyridine-3-one (C2), and 2-(sec-butyl)-7,8-dimethoxybenzo[de]imidazo[4,5,1-ij][1,6]-naphthyridin-10(9H)-one (C3) were theoretically studied by density functional theory (DFT). Direct antioxidant activities of C1–C3 were firstly evaluated via their intrinsic thermochemical properties and radical scavenging activity of the potential antioxidants with the HOO●/HO● radicals via four mechanisms, including: hydrogen atom transfer (HAT), single electron transfer (SET), proton loss (PL) and radical adduct formation (RAF). Kinetic calculation reveals that HOO● scavenging in water is occurred via HAT mechanism with C1 (kapp, 7.13x106 M-1 s-1) while RAF is more dominant with C2 (kapp, 1.40x105 M-1 s-1) and C3 (kapp, 2.90x105 M-1 s-1). Antioxidant activity of aaptamine derivatives can be classified as C1 > C3 > C2. Indirect antioxidant properties based on Cu(I) and Cu(II) ions chelating activity were also investigated in aqueous phase. All three studied compounds show spontaneous and favorable Cu(I) ion chelating activity with DG0 being -15.4, -13.7, and -15.7 kcal.mol-1, whereas DG0 for Cu(II) chelation are -10.4, -10.8, and -2.2 kcal.mol-1 for C1, C2 and C3, respectively. In addition, all compounds show UVA and UVB absorption; in which the excitations are determined mostly as π-π* transition. Overall, the results suggest the potential applications of the aaptamines in pharmaceutics and cosmetics, i.e. as sunscreen and antioxidant ingredient.

Biogenic amines are involved in physiological roles in living organisms, but their excessive production or intake can induce undesired toxicological effects. As biogenic amines can be found in the process of food spoilage, they are considered an indicator of food quality and freshness, and their detection is of crucial importance in food safety. In this contribution, we report the fast and direct colorimetric and fluorometric sensing of biogenic amines by means of a dinuclear Zn(ii) Schiff-base complex. The selective and sensitive detection involves the formation of stable adducts between the dinuclear complex, acting as the Lewis acidic molecular tweezer, and biogenic di- or polyamines. The selectivity towards biogenic amines, even in the presence of common aliphatic, primary, secondary, or tertiary monoamines, heterocyclic amines, and amino acids, is demonstrated by competitive experiments. The quantitation of histamine in a fish matrix is easily achieved using a standard extraction procedure followed by simple colorimetric or fluorometric measurements.

Five luminescent polymorphic aggregates of trinuclear Cu(I)–pyrazolate, namely [anti-Cu3L3]2 (1), [syn-Cu3L3·C2H5OH]2 (2), [anti-Cu3L3·C2H5OH]n (3), [anti-Cu3L3·0.5C7H8]n (4) and [syn-Cu3L3·C8H10]n (5) (HL = 4-(pyridin-4-ylthio)-3,5-dimethyl-1H-pyrazole), were reported. The trimeric Cu3L3 fragments present syn- and anti-conformations dependent on the dangled direction of 4-pyridyl groups on the two sides of the Cu3Pz3 plane (Pz = pyrazolate). Intertrimeric NPy⋯Cu weak coordination bonds associate these Cu3L3 fragments together to form dimeric or polymeric structures, which are further stabilized by crystallized solvent molecules or intertrimeric Cu⋯Cu interactions. The solvated complexes (3–5) may be transformed into the unsolvated complex 1 by evacuation of the crystallized solvents upon heating. All these complexes emit from green to yellow under UV irradiation, which originated from the triplet excited states of metal to ligand charge transfer (3MLCT) mixed with intertrimeric Cu⋯Cu interactions. This work provides a novel kind of supramolecular aggregate based on Cu3Pz3 beyond the classical π-acid⋯base adducts and metallophilicity-dependent dimers/oligomers.

This manuscript reports the synthesis, X-ray characterization and DFT study of a series of all-cis 1,4:2,3:5,8:6,7-tetraepoxynaphthalenes (decahydro-2,6:3,5-diepoxynaphtho[2,3-b:6,7-b′]bis(oxirene) derivatives) obtained by the tandem [4 + 2] cycloaddition between dimethyl acetylenedicarboxylate (DMAD) and three difurans as bis-dienes (the IMDAF reaction). The “pincer”-type adduct formation is controlled by using kinetic conditions. For this work, we were only interested in the synthesis of “pincer”-type adducts to study the formation self-assembled dimers that are governed by quite short C–H⋯O H-bonds. The existence of the “through-space” alpha-effect in the “pincer”-type adducts increases their ability to establish bifurcated C–H⋯O2 H-bonds in the solid state. That is, the close distance between the O-bridge atoms provokes an interesting through space lone pair⋯lone pair (LP⋯LP) interaction that increases the H-bond acceptor ability of the O-atoms. It has been analyzed using DFT calculations, molecular electrostatic potential (MEP) surfaces, quantum theory of atoms-in-molecules (QTAIM) and noncovalent interaction plot (NCIplot) index computational tools. This is the second study of the literature where “alpha-effect” hydrogen bonds (AEHBs) are described and studied. The novelty of the present work resides in the exhaustive epoxidation of the double bonds in the resulting “pincer”-type adducts that increases the number of possible H-bond acceptors in the target vicinal tetra-epoxynaphthalenes. The X-ray analyses of the three synthesized tetra-epoxides reveal that the AEHBs are predominant in the solid phase.

1,3-Phosphaazaallenes are heteroallenes of the type RP Created by potrace 1.16, written by Peter Selinger 2001-2019 CNR′ and little is known about their reactivity. In here we describe the straightforward synthesis of ArPCNR (Ar = Mes*, 2,4,6-tBu-C6H2; MesTer, 2.6-(2,4,6-Me3C6H2)–C6H3; DipTer, 2.6-(2,6-iPr2C6H2)–C6H3; R = tBu; Xyl, 2,6-Me2C6H3) starting from phospha-Wittig reagents ArPPMe3 and isonitriles CNR. It is further shown that ArPCNtBu are thermally labile with respect to the loss of iso-butene and it is shown that the cyanophosphines ArP(H)CN are synthetically feasible and form the corresponding phosphanitrilium borates with B(C6F5)3, whereas deprotonation of DipTerP(H)CN was shown to give an isolable cyanidophosphide. Lastly, the reactivity of ArPCNR towards Pier's borane was investigated, showing hydroboration of the CN bond in Mes*PCNtBu to give a hetero-butadiene, while with DipTerPCNXyl the formation of the Lewis acid–base adduct with a B–P linkage was observed., The combination of phospha-Wittig reagents with isonitriles affords 1,3-phosphaazaallenes and their diverse reactivity has been studied in detail.

The dried plant of Tadehagi triquetrum is called Hulu Tea in traditional Chinese medicine (TCM). This study attempted to analyze the antioxidant products of the interaction with cellular reactive oxygen species. LAEH, a lyophilized aqueous extract of Hulu Tea, was prepared and analyzed using high-performance liquid chromatography. Eight phytophenols were found, namely, rutin, isoquercitrin, p-coumaric acid, p-hydroxybenzoic acid (pHBA), kaempferol, protocatechuic acid, afzelin, and daidzein. The antioxidant levels of the phytophenols were evaluated using the 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO˙) trapping, 1,1-diphenyl-2-picryl-hydrazl (DPPH˙) trapping, Fe3+-reducing, and Cu2+-reducing assays. The reaction products of DPPH˙ with phytophenols were further analyzed using ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC-ESI-Q-TOF-MS/MS). A series of molecular ion and fragment peaks were observed, which corresponded to seven phytophenol–DPPH adducts, four phytophenol–phytophenol homodimers, and one p-coumaric acid–pHBA heterodimer. Seven possible heterodimer linking sites were further calculated using computational chemistry based on density functional theory with the methanol solvation model at the B3LYP (or UB3LYP)-D3/6-311+G(d,p) level. However, the 2,2′-linking heterodimer possessed the lowest enthalpy change (ΔH) value of −69.54 kcal mol−1; the 2,2′-bond presented a Laplacian bond order value of 1.083 and a bond length of 148.9 pm. In conclusion, the eight antioxidant phytophenols can produce three types of antioxidant products, phytophenol–radical adduct, phytophenol–phytophenol homodimer, and phytophenol–phytophenol heterodimer. The phytophenol–phytophenol heterodimer refers to the p-coumaric acid–pHBA 2,2′-linking heterodimer rather than the 2-8′ benzofuran p-coumaric acid/pHBA heterodimer.

Cyclotriarsanes are rare and limited synthetic approaches have hampered reactivity studies on these systems. Described in here is a scalable synthetic protocol towards (AsAr)3 (Ar = Dip, 2,6-iPr2-C6H3; Tip, 2,4,6-iPr3-C6H2), which allowed to study their reactivity towards [Cp2Ti(C2(SiMe3)2], affording titanocene diarsene complexes and towards N-heterocyclic carbenes (NHCs) to give straightforward access to a variety of NHC-arsinidene adducts. The electronic structure of the titanium diarsene complxes has been studied and they are best described as Ti(IV) species with a doubly reduced As2Ar2 ligand. These findings will make (AsAr)3 valuable precursors in the synthetic inorganic and organic chemistry.

The first phosphinoboronic ester bearing a fused bicyclic framework was synthesised by either deprotonation and hydride abstraction or Rh-catalysed dehydrogenation of a hydrophosphineboronic ester. The phosphinoboronic ester reacted as a Lewis acid with KF/18-crown-6, pyridine and DMAP to give the corresponding adducts. Furthermore, its crystal structure shows a remarkably short P-B bond in comparison with other P-B bonded derivatives in spite of the trigonal pyramidal geometry of the phosphorus. Consistent with the phosphorus pyramidality, the π-type donor-acceptor interaction of the P-B bond is small as revealed by the DFT calculations. The P-B bond shared within the fused six-membered rings has to shorten because of the geometrical requirement and high s-character of the boron.

In this work, we describe the application of a synthetic enzyme (synzyme) as the catalyst to promote the multicomponent synthesis of isoxazol-5(4H)-one derivatives. The catalytic system could be used up to 15 times without any notable loss of its activity. Some derivatives showed fluorescence and their photophysical data were evaluated. The mechanism of the reaction was, for the first time, investigated and, among the three reaction pathway possibilities, only one was operating under the developed conditions. ESI-MS(/MS) allowed for both the simultaneous monitoring of the multicomponent reaction (MCR) and the proposition of a kinetic model to explain the transformation. The kinetic model pointed firmly to only one reaction pathway and helped to discard the other two possibilities. The antimicrobial abilities of all synthesized derivatives against Gram-positive and Gram-negative strains were also evaluated. The abilities of functional chromophores (fluorescent compounds) as live cell-imaging probes were verified and one of the multicomponent adducts could stain early endosomes selectively in bioimaging experiments.

Organic–inorganic hybrid perovskites have attracted intensive attention due to their exceptional optoelectronic properties. With a massive leap of efficiency from 3.8% to 25.2% in a decade, perovskite solar cells (PSCs) have been considered the most promising next-generation photovoltaic technology. Recently, the methylamine (MA)-gas-mediated approach has been widely studied for preparing precursor solutions to deposit large scale perovskite thin films for PSCs. In this article, high-quality MAPbI3 films were spin-coated using a MA-gas-mediated perovskite precursor. The deposited MAPbI3 films showed larger crystal grains, lower surface roughness, and a preferred (110) crystal orientation compared to the films deposited by the Lewis adduct method. Planar PSC devices fabricated using the MA-gas-mediated precursor showed a high efficiency of 19.28% and a higher average efficiency than the devices fabricated by the Lewis adduct method.

A family of hexakis-substituted [60]fullerene adducts endowed with the well-known tridentate 2,6-bis(pyrazol-1-yl)pyridine (bpp) ligand for spin-crossover (SCO) systems has been designed and synthesized. It has been experimentally and theoretically demonstrated that these molecular scaffolds are able to form polynuclear SCO complexes in solution. UV-vis and fluorescence spectroscopy studies have allowed monitoring of the formation of up to six Fe(ii)–bpp SCO complexes. In addition, DFT calculations have been performed to model the different complexation environments and simulate their electronic properties. The complexes retain SCO properties in the solid state exhibiting both thermal- and photoinduced spin transitions, as confirmed by temperature-dependent magnetic susceptibility and Raman spectroscopy measurements. The synthesis of these complexes demonstrates that [60]fullerene hexakis-adducts are excellent and versatile platforms to develop polynuclear SCO systems in which a fullerene core is surrounded by a SCO molecular shell., Polynuclear spin-crossover molecules showing both thermal and photoinduced spin transitions have been prepared using a [60]fullerene hexakis-adduct endowed with Fe(ii) complexes of tridentate 2,6-bis(pyrazol-1-yl)pyridine (bpp) ligand.

With the radical derived from alkyl silicates or 4-alkyl-1,4-dihydropyridines as the surrogate for the nucleophile, the cyclisation of 2-(1-alkynyl)-2-alken-1-ones proceeds smoothly via consecutive reductive radical-polar crossover and cycloisomerization processes enabled by dual photoredox–copper catalysis. Both single-electron oxidation and reduction occur between the photocatalyst and radical precursor/adduct radical, generating the enolate ion without the need for a base and an exogenous oxidant–reductant. In contrast to the reported transition-metal catalysed cyclisation with the oxonium ion as the key intermediate, the nucleophilic attack of enolate-oxygen on the copper coordinated alkyne was proposed for this dual catalysis. This new methodology for the preparation of polyfunctional furans features mild conditions, a broad substrate scope, and good functional group tolerance.

Treatment of 3a,6a-diaza-1,4-diphosphapentalene (DDP) with an excess of PhBCl2 yields the corresponding bis(borane) adduct DDP(PhBCl2)2 (14), demonstrating the availability of two lone pairs on the phosphorus center. The reaction between DDP and B(C6F5)3 yields (1 : 1) phosphino-borane complex 16. The free lone electron pair on the pyramidal P atom in 16 participates in the intramolecular non-covalent interactions P(1)⋯F(1) and P(1)⋯F(6) giving additional 3.9 and 2.8 kcal mol−1, respectively, for stabilization of the complex. This through-space interaction appears in the 31P NMR spectrum as large spin–spin coupling constants of 271 and 219 Hz. The addition of water to 16 (1 : 1) leads to the formation of the insertion product 17 having –H2P–O–B(C6F5)3 moiety. The reaction of DDP with BH3·SMe2 proceeds in several stages, which include the insertion of the masked phosphinidene into the B–H and P–H bonds of the intermediate compounds followed by the dehydrocoupling step and formation of diphosphine 18. The last compound exists in solution as a set of stereoisomers.

The two-electron and two-proton p-hydroquinone/p-benzoquinone (H2Q/BQ) redox couple has mechanistic parallels to the function of ubiquinone in the electron transport chain. This proton-dependent redox behavior has shown applicability in catalytic aerobic oxidation reactions, redox flow batteries, and co-electrocatalytic oxygen reduction. Under nominally aprotic conditions in non-aqueous solvents, BQ can be reduced by up to two electrons in separate electrochemically reversible reactions. With weak acids (AH) at high concentrations, potential inversion can occur due to favorable hydrogen-bonding interactions with the intermediate monoanion [BQ(AH)m]˙−. The solvation shell created by these interactions can mediate a second one-electron reduction coupled to proton transfer at more positive potentials ([BQ(AH)m]˙− + nAH + e− ⇌ [HQ(AH)(m+n)−1(A)]2−), resulting in an overall two electron reduction at a single potential at intermediate acid concentrations. Here we show that hydrogen-bonded adducts of reduced quinones and the proton donor 2,2,2-trifluoroethanol (TFEOH) can mediate the transfer of electrons to a Mn-based complex during the electrocatalytic reduction of dioxygen (O2). The Mn electrocatalyst is selective for H2O2 with only TFEOH and O2 present, however, with BQ present under sufficient concentrations of TFEOH, an electrogenerated [H2Q(AH)3(A)2]2− adduct (where AH = TFEOH) alters product selectivity to 96(±0.5)% H2O in a co-electrocatalytic fashion. These results suggest that hydrogen-bonded quinone anions can function in an analogous co-electrocatalytic manner to H2Q.

A dual optimization salification strategy has been established for the purpose of taking advantages of the nutrient ferulic acid (FD) to perfect the in vivo/vitro peculiarities of the antiviral drug, namely amantadine hydrochloride (AIN·HCl). The strategy uses FD as the hydrophobic counter anion to react with free alkali (AIN) of AIN·HCl, making the highly soluble AIN·HCl turn into molecular salt with lower solubility. Moreover, the antiviral efficacy is elevated by playing FD's preponderance for possessing assistant antiviral capacity, realizing the synergistically increased antiviral effects of the two ingredients. Taking the strategy as guidance, a new molecular adduct of AIN and FD with isopropanol (IPA) solvent, namely AIN-FD-IPA, is synthesized and characterized as the first antiviral drug-nutrient molecular salt. Single-crystal X-ray diffraction analysis shows that the prepared molecular salt is assembled by strong charge-assisted hydrogen bonds to a sandwich layer structure, which is beneficial toward making the solubility and dissolution rate of the present molecular salt become concurrently down-regulated in comparison with AIN·HCl. Interestingly, the reduced in vitro dissolubility can be converted into a lengthened retention time and enhanced bioavailability in vivo, thus eliminating the side effects originating from the excessive solubility of the native AIN·HCl. More significantly, the molecular salt also exhibits greatly enhanced antiviral effects against the tested viral strains due to the cooperativeness of AIN and FD. Consequently, the current investigation not only supplies a new tactic for traditional antiviral drug AIN·HCl to down-regulate its excessive solubility for reducing the toxic side effect, and simultaneously enhances its antiviral effects via the double optimized hydrophobic molecular salt formation, but also offers an opportunity for phenolic acid nutrients in the application of synergistic antiviral drugs.

Weakly Coordinating Anions (WCAs) facilitate the formation of exotic “naked” cationic species. However, the feasibility of the respective synthesis approaches may be limited by the basicity of the solvent utilized, as the latter is one of the most important factors determining the solvation ability. In this work, we focus on a series of novel complexes of Ag(I) and Cu(I) with weakly basic ligands such as CH2Cl2, Cl3CCN and SO2 stabilized by perfluorinated alkoxyaluminate, Al[(ORF)4]−, RF = C(CF3)3. The discussion includes their synthesis protocols, crystal structures, vibrational spectra and thermal stability (TGA/DSC/EGA). We show that the Cu–SO2 adducts present exceptional stability in relation to other metal–SO2 complexes. To broaden the scope of weakly basic ligands which could prove helpful in the development of chemistry with WCAs, the screening of potential candidates based on DFT calculations is presented.

RuCl2(P–OP)(N–N) complexes (1) containing an atropisomerizable phosphine–phosphite (P–OP) and a chiral C2 symmetric diamine (N–N) are readily prepared as trans isomers by successive addition of P–OP and N–N ligands to RuCl2(PPh3)3. For these complexes, fast atropisomerization of the biaryl fragment at room temperature has been observed. Compound trans-1a cleanly isomerizes into a mixture of cis isomers in EtOH upon heating. DFT calculations reproduce accurately the ratio of isomers observed as well as the greater thermodynamic stability of the cis isomers of 1a. Complexes 1 are efficient catalyst precursors for the asymmetric hydrogenation of N-aryl imines 5 in toluene under very mild conditions using KOtBu as a base (4 bar H2, room temperature, 5/1/KOtBu = 500/1/10). Among the catalyst precursors, 1f provides good enantioselectivities in the hydrogenation of a wide range of N-aryl imines (84–96% ee, 16 examples). From DFT calculations, a mechanism consisting in stepwise transfer of a hydride and a proton from the dihydride to the imine has been proposed, with the most favourable paths for R and S products involving cis-dihydrides d1R and d3S, respectively. Among several hydrogen activation pathways examined in the pro-R route, the most favorable one consists of hydrogen coordination to a Ru–amido/amine adduct, followed by amine assisted activation of dihydrogen

Phosphorescent PtII-based cyclometalated complexes co-crystallise with bromo- and iodosubstituted perfluorinated arenes to give 1 : 1 adducts. X-FArenes in these co-crystals act as both σh and πh donors forming co-operative C–X⋯Cl–Pt XBs and πh⋯dz2[PtII] contacts. The solid-state photophysical study revealed up to a 2-fold luminescence quantum yield increase upon co-crystallisation due to the formation of these co-operative noncovalent interactions.

The three isomeric tetraarylethylene derivatives DPDT-o-CHO, DPDT-m-CHO and DPDT-p-CHO have been designed and synthesized, based on a 1,1-diphenyl-2,2-(2-dithiophen) ethylene (DPDT) core doubly bonded to the phenyl group with an ortho-/meta-/para-aldehyde substituent for unique aggregation-induced emission (AIE)-active luminescences. They exhibited remarkable photochromic behaviors based on the UV-light induced photocyclization reaction, including fluorescence enhancement in solution and emission quenching in the solid state. Moreover, the positions of the substituent aldehyde group exert distinct influence on their molecular conformation and spatial arrangement, resulting in distinct photoresponse. Interestingly, the solid-state of meta-substituted isomer DPDT-m-CHO undergoes a fast reversible photo-switch with a high colorimetric contrast and exhibited a rewritable process on filter paper, which highlight the advantage of these AIE-active photochromic molecules in various practical applications. In addition, owing to the reaction of the aldehyde group with hydrogen sulfite (HSO3−) to generate ionic adducts triggering the disaggregation process, the three AIE-active luminogens were capable of exhibiting a “turn-off” fluorescence response to hydrogen sulfite in high water content. Our work provides a general method to design aldehyde group functionalized regioisomeric AIE luminogens with photochromic features by the controllable UV-light induced photocyclization reaction and fluorescence quenching by reverse chemical reaction-based disaggregation, indicating the prospective applications of these luminogens in information security and specific fluorescence sensing.

Due to the powerful reducing ability of the metal active site, low-valent uranium complexes show remarkable performance in activating thermodynamically stable and kinetically inert small molecules. In this work, experimentally known uranium metallocenes [Cp3U]z (z = 0 and +1) were intensively studied using relativistic density functional theory for their activation of small molecules (X = CO2, N2, CO and NO). Regardless of whether z = 0 or +1, a weak double bond was realized between uranium and NO, which is in agreement with a previous study; a weak single bond with the dative nature was assigned to other small-molecule uranium adducts. A general order for the uranium–small molecule bond strength, NO > CO > N2 > CO2, has been built, the trend being exactly the same as the computed reduction potentials. These are corroborated by energetics and experimental results that (i) analogues of the first three [Cp3U(X)] adducts were crystallographically identified but the one of [Cp3U(CO2)] was not, and (ii) much higher X gas pressure was required to synthesize [Cp3U(N2)] than for [Cp3U(CO)]. Additionally, the experimentally inaccessible CO2 adduct was rationalized using thermodynamic and kinetic calculations as well as geometric/electronic properties and bonding analyses.

Novel chiral derivatising agents (CDAs) such as methyl itaconate–anthracene adducts (MIAs) were reported for the absolute configuration determination of chiral secondary alcohols by the 1H NMR technique. These adducts were facilely prepared through well-known reactions, and furthermore, commercially available starting materials. According to these synthetic routes, the desired MIAs were afforded in 6 steps with 49% overall yield from dimethyl itaconate. Moreover, the represented MIAs provided significantly large differences of chemical shift values (ΔδSR). No racemisation from the tertiary characteristics of the adjacent alpha carbon was observed.

A novel selectively sequential C–S/C–N bond activation is presented. Through the combination of an Ugi-4CR and sequential C–S/C–N bond cleavage, diverse peptidomimetics containing a primary amide are prepared in a rapid, highly efficient and step-economical manner. This approach exhibits high yield, excellent chemoselectivity and functional group tolerance. Compounds derived from the pharmaceuticals febuxostat, probenecid and memantine as well as β-amino acid are prepared. This method provides a new direction for the synthesis of peptidomimetics.

Glycosyl fluorides as glycosylating agents have been widely applied in constructing diverse glycosidic bonds, however, catalytic glycosylation of disarmed glycosyl fluorides is largely undeveloped. Herein, we describe catalytic (C6F5)3B·(H2O)n-initiated glycosylation of a wide range of disarmed glycosyl fluorides and reverse glycosyl fluorides with a variety of O- and C-nucleophiles. The reactions proceed smoothly under the mild reaction conditions and provide the desired glycosides in good-to-excellent yields. The transformations enjoy a broad substrate scope and accommodate the functional groups used frequently in carbohydrate chemistry. Preliminary mechanistic studies suggest that the adduct (C6F5)3B·(HF)n, in situ generated from the ligand exchange of (C6F5)3B·(H2O)n with the HF delivered during the reaction, might be the actual catalyst in the reaction. The species represents a new Lewis acid-assisted Bronsted acid with enough acidity to effect catalytic glycosylation of disarmed glycosyl fluorides. Configuration-controlled one-pot synthesis of oligosaccharides is achieved based on difference in reactivity of β-glycosyl fluorides and their α-congeners relying on (C6F5)3B·(HF)n catalysis.

The N–H deprotonation of the diaminodialkoxido diborane(4) pinB–Bdab (1) (pin: (OCMe2)2, dab: 1,2-(NH)2C6H4), is crucial for the electrophilic N-functionalisation towards unsymmetrical diborane(4) reagents. An N–H deprotonated diborane(4) comprises Lewis basic nitrogen atoms and at the same time Lewis acidic boron atoms. This bifunctionality governs its reactivity and structural chemistry. Whilst bases such as Na(hmds), tBuLi or Li(tmp) readily effect a single deprotonation of 1, the second deprotonation is less straightforward and cleanly only achieved with Li(tmp) as a strong but little nucleophilic base. The N–H deprotonated diborane(4) derivatives readily dimerise to give B(sp2)2B(sp3)2N2 six-membered ring Lewis base adducts. The structural chemistry of this class of compounds was studied in detail in the solid state by single crystal X-ray diffraction as well as in solution by NMR spectroscopy.

Arsenoplatin-1 (AP-1) is an innovative dual-action anticancer agent that contains a platinum(ii) center coordinated to an arsenous acid moiety. We found that AP-1 spontaneously aggregates in aqueous solutions generating oligomeric species of increasing length. Afterward, we succeeded in solving the crystal structure of the adduct formed between the model protein lysozyme and an early AP-1 oligomer that turned out to be a trimer. Remarkably, this crystal structure traps an early stage of AP-1 aggregation offering detailed insight into the molecular process of the oligomer's growth.

A bifunctional amino sulfonamide-catalyzed asymmetric conjugate addition of aldehydes to alkenyl alkynyl ketimines as reactive surrogates for enones has been developed. Use of a phenylcyclopropane-based amino sulfonamide catalyst, which can activate and orient the ketimines through hydrogen bonding, affords the desired conjugate adducts with high chemo-, diastereo- and enantioselectivity.