Triple Bond Research Articles

Mapping the Binary Covalent Alloy Space to Pursue Superior Nitrogen Reduction Reaction Catalysts

AbstractThe electrochemical nitrogen reduction reaction (NRR) has the potential to decarbonize industrial ammonia production. However, NRR has poor activity and selectivity versus the competing hydrogen evolution reaction for catalysts that adhere to scaling relations. Overcoming the limitations imposed by scaling relations requires more complex catalyst materials, however, evaluating materials beyond simple metal systems is a large combinatorial problem that requires an improved understanding of the electrocatalyst surface to rationally guide the discovery of superior catalysts. The study uses grand canonical density functional theory to uncover NRR trends on a large and disparate set of binary covalent alloys (BCA) with variable compositions and active‐site geometries. The studied BCAs generally follow scaling relations, albeit with larger variance and several systems that significantly break scaling. BCAs with early‐ to mid‐transition metals tend to lie near the volcano peak and activate the N2 triple bond via a side‐on binding configuration. Trends in the BCA space cannot be readily predicted using simple electronic descriptors, which is ascribed to the large geometric variability of the BCA surfaces. It is anticipated that these findings will provide a foundation for the rational design of superior NRR electrocatalysts with increasing material complexity.

Selective Reduction of Triple Bond via Proton-Coupled Electron Transfer for the Synthesis of α,β-Unsaturated γ-Lactams.

Described herein is the development of a visible-light-induced photoredox 1,6-enyne reductive cyclization via selective reduction of a triple bond instead of an activated double bond. The selective 1,6-enyne radical cyclization/carbon═carbon double bond cleavage provided a straightforward route to structurally valuable α,β-unsaturated γ-lactams. TEMPO-trap experiments, control experiments, and DFT calculations have offered evidence supporting the possible catalytic cycle.

Triple Bond Species in the Synthesis of Oxa(thia)diazoles and Triazoles (A Review)

Triple Bond Species in the Synthesis of Oxa(thia)diazoles and Triazoles (A Review)

ВЛИЯНИЕ СТРОЕНИЯ ЛИНЕЙНЫХ УГЛЕВОДОРОДОВ НА ТЕМПЕРАТУРУ САМОВОСПЛАМЕНЕНИЯ

Using experimental data available in the literature the auto-ignition temperature of saturated and unsaturated hydrocarbons with different molecular structures is analyzed. Based on modern research of hydrocarbons oxidation with different structures at high temperatures, the connection between chemical structure, bond strength in the molecule and radical mechanisms of oxidation processes with the auto-ignition temperature is shown. It is noted that the branching of molecules contributes to the temperature of self-ignition increase, that is, an increase in their composition of methyl groups, tertiary and quaternary carbon atoms located nearby in the carbon chain. Double and triple bonds, starting from C5, strengthen the molecule. The elongation of both the main chain and the chain of substituents reduces the auto-ignition temperature of the compound.

Nickel binding enables isolation and reactivity of previously inaccessible 7-aza-2,3-indolynes.

N-Heteroaromatics are key elements of pharmaceuticals, agrochemicals, and materials. N-Heteroarynes provide a scaffold to build these essential molecules but are underused because five-membered N-heteroarynes have been largely inaccessible on account of the strain of a triple bond in that small of a ring. On the basis of principles of metal-ligand interactions that are foundational to organometallic chemistry, in this work we report the stabilization of five-membered N-heteroarynes in the nickel coordination sphere. A series of 1,2-bis(dicyclohexylphosphino)ethane nickel 7-azaindol-2,3-yne complexes were synthesized and characterized crystallographically and spectroscopically. Ambiphilic reactivity of the nickel 7-azaindol-2,3-yne complexes was observed with multiple nucleophilic, electrophilic, and enophilic coupling partners.

Activating Nitrogen for Electrochemical Ammonia Synthesis via an Electrified Transition-Metal Dichalcogenide Catalyst.

The complex interplay between local chemistry, the solvent microenvironment, and electrified interfaces frequently present in electrocatalytic reactions has motivated the development of quantum chemical methods that can accurately model these effects. Here, we predict the thermodynamics of the nitrogen reduction reaction (NRR) at sulfur vacancies in 1T'-phase MoS2 and highlight how the realistic treatment of potential within grand canonical density functional theory (GC-DFT) seamlessly captures the multiple competing effects of applied potential on a catalyst interface interacting with solvated molecules. In the canonical approach, the computational hydrogen electrode is widely used and predicts that adsorbed N2 structure properties are potential-independent. In contrast, GC-DFT calculations show that reductive potentials activate N2 toward electroreduction by controlling its back-bonding strength and lengthening the N-N triple bond while decreasing its bond order. Similar trends are observed for another classic back-bonding ligand in CO, suggesting that this mechanism may be broadly relevant to other electrochemistries involving back-bonded adsorbates. Furthermore, reductive potentials are required to make the subsequent N2 hydrogenation steps favorable but simultaneously destabilizes the N2 adsorbed structure resulting in a trade-off between the favorability of N2 adsorption and the subsequent reaction steps. We show that GC-DFT facilitates modeling all these phenomena and that together they can have important implications in predicting electrocatalyst selectivity for the NRR and potentially other reactions.

The Noble Addendum of a Phosphenium Ligand to a Base Metal: Coordination, Activation, and Hydrogenation of Alkenes and Alkynes on a Chromium Complex.

The synthesis of a new bis-NHP complex (NHP=N-heterocyclic phosphenium) of chromium via salt metathesis and studies of its reactivity are reported. Photochemical reactions with H2 and selected olefins give rise to non-isolable H2- and π-alkene complexes identified spectroscopically, while internal alkynes react via activation of the triple bond to yield isolable metalla-phospha-cyclobutenes characterized by spectroscopic and XRD data. DFT studies give a preliminary account of the bonding in H2- and alkene-complexes and explain the different reactivity towards alkenes and alkynes as the consequence of kinetic effects. Photolysis of the bis-NHP-complex in the presence of H2 and olefins or alkenes enables the catalytic hydrogenation of the organic substrates, while the π-ethene complex mediates the catalytic hydrogenation of ethene in a dark reaction. The similarities and differences between both catalytic processes are shortly discussed.

One‐Pot Gold/Acid‐Catalyzed Synthesis of Indolo[1,2‐a]quinolin‐5(6H)‐ones from 1‐(2‐Ethynylphenyl)‐1H‐indoles

AbstractWe present a method for the synthesis of substituted indolo[1,2‐a]quinoline‐5(6H)‐ones starting from 1‐(2‐ethynylphenyl)‐1H‐indoles. The transformation involves gold‐catalyzed oxidation of the triple bond followed by acid‐promoted intramolecular cyclization at the indole C2 position. Demonstrating noteworthy versatility, the reaction tolerates a wide array of substituents on the indole core and proceeds in good to excellent yields (up to 93 %).

Synthesis, crystal and structural studies of 5-alkynyl-1,2,3-triazoles

The structures of diverse 5-alkynyl-1,2,3-triazoles were analyzed by the conventional spectroscopic techniques and corroborated by X-ray diffraction analyses. In addition, Hirshfeld surface analysis was carried out on these compounds, highlighting the presence of π−π stacking interactions together with a C–H–N triazole-methylene interaction observed in compound 3 as the main intermolecular interactions which define the crystal packing and supramolecular network in these compounds. Further theoretical calculations of global descriptors and molecular electrostatic maps demonstrate a charge distribution connecting phenyl substituents, triazole ring and the triple bond which is related to π−π stacking interactions supporting experimental observations.

Influence of external electric field on properties of Cyclotriparaphenyl[6]carbon

Cyclotriparaphenyl[6]carbon is a hypothetical derivative compound of cyclo[12]carbon, in which three CC triple bonds are replaced by three benzene rings. Comprehensive investigations of influence of external electric field (EEF) on cyclotriparaphenyl[6]carbon have been performed from theoretical aspect in this work. The maximum appropriate applied electric field strength is 0.0265 a.u., electron detachment will occur when EEF exceeds this value. When the EEF is in the range of 0–0.0265 a.u., with the increase of EEF, the shape of cyclotriparaphenyl[6]carbon turns from a circle to oval, the HOMO-LUMO gap gradually decreases from 6.046 eV at 0 a.u. to 2.322 eV at 0.0265 a.u., and its absorption band extends to VL (visible light) region and near-infrared region little by little. When the EEF are 0.025 a.u. and 0.0265 a.u., its maximum absorption wavelengths are 1220.6 nm and 1383.5 nm, respectively. HOMA (Harmonic oscillator measure of aromaticity), AV1245 and electron localization function (ELF) calculation results indicate that cyclotriparaphenyl[6]carbon has no aromaticity in the EEF range of 0–0.0265 a.u.. The compound exhibitspromising potential forapplication inthefield of colordevelopingcompound materials.

The reaction of nonacarbonyldiiron with 8‐alkynyloxyquinolines: Alkynyl activation, cyclization via C‐N bond formation, and C‐H bond cleavage

In this work, the reactions of nonacarbonyldiiron with 8‐alkynyloxyquinoline ligands (L1‐L3) and their resultant iron carbonyl complexes (1a, 1b, 2, and 3) are described. The complexes including the ligands were fully characterized by using a variety of spectroscopic techniques. The four complexes were also crystallographically determined. In the reactions, the quinoline N atom underwent cyclization to form a quinolinium skeleton while the C‐H bond of the quinoline at position 2 or the substituted methyl group was cleaved to form Fe‐C bond(s). Meanwhile, the alkynyl triple bond was reduced to a single bond (1a) or double bonds (1b, 2, and 3) to further coordinate the iron in σ‐bonds or η‐bonds. Particularly, pathways of hydrogenation (1a and 2) and/or dehydrogenation (1b and 3) were accompanied by the reactions. Moreover, the oxidation states of the iron centers in these complexes were identified through analyses of their bond formation, FTIR and NMR spectroscopic signals (1H NMR and DEPT‐135) in combination with their diamagnetic nature, that is, iron (0) for 2 and iron (I) for the rest of the diiron complexes.

Fabrication of gelatin-polyester based biocomposite scaffold via one-step functionalization of melt electrowritten polymer blends in aqueous phase

The rapid manufacturing of biocomposite scaffold made of saturated-Poly(ε-caprolactone) (PCL) and unsaturated Polyester (PE) blends with gelatin and modified gelatin (NCO-Gel) is demonstrated. Polyester blend-based scaffold are fabricated with and without applying potential in the melt electrowriting system. Notably, the applied potential induces phase separation between PCL and PE and drives the formation of PE rich spots at the interface of electrowritten fibers. The objective of the current study is to control the phase separation between saturated and unsaturated polyesters occurring in the melt electro-writing process and utilization of this phenomenon to improve efficiency of biofunctionalization at the interface of scaffold via Aza-Michael addition reaction. Electron-deficient triple bonds of PE spots on the fibers exhibit good potential for the biofunctionalization via the aza-Michael addition reaction. PE spots are found to be pronounced in which blend compositions are PCL-PE as 90:10 and 75:25 %. The biofunctionalization of scaffold is monitored through CN bond formation appeared at 400 eV via X-ray photoelectron spectroscopy (XPS) and XPS chemical mapping. The described biofunctionalization methodology suggest avoiding use of multi-step chemical modification on additive manufacturing products and thereby rapid prototyping of functional polymer blend based scaffolds with enhanced biocompatibility and preserved mechanical properties. Additionally one-step additive manufacturing method eliminates side effects of toxic solvents and long modification steps during scaffold fabrication.

Stereoselective Reduction of Conjugated and Non-conjugated Triple Bonds in Attractant Precursors with Zn Activated by Cu: A Designed Approach to the Synthesis of Conjugated Dienic Pheromones

AbstractA simple, highly stereoselective, and efficient method to obtain important attractants by the reduction of the triple bond in several E-enynes and hex-3-ynyl acetate by an activated Zn-Cu system is described. The stereoselectivity of the semireduction for the generation of a new (Z)-C=C bond was >98%. The substrates for the reduction reaction were obtained by new synthetic routes with an overall yield of more than 40%.

Exploring the impact of stress on the electronic structure and optical properties of graphdiyne nanoribbons for advanced optoelectronic applications

Graphdiyne (GDY), a two-dimensional carbon material with sp- and sp2-hybridization, is recognized for its unique electronic properties and well-dispersed porosity. Its versatility has led to its use in a variety of applications. The precise control of this material's properties is paramount for its effective utilization in nano-optical devices. One effective method of regulation, which circumvents the need for additional disturbances, involves the application of external stress. This technique provides a direct means of eliciting changes in the electronic characteristics of the material. For instance, when subjected to uniaxial stress, electron transfer occurs at the triple bond. This results in an armchair-edged graphdiyne nanoribbon (A(3)-GDYNR) with a planar width of 2.07 nm, which exhibits a subtle plasmon effect at 500 nm. Conversely, a zigzag-edged graphdiyne nanoribbon (Z(3)-GDYNR) with a planar width of 2.86 nm demonstrates a pronounced plasmon effect within the 250–1200 nm range. This finding suggests that the zigzag nanoribbon surpasses the armchair nanoribbon in terms of its plasmon effect. First principles calculations and ab initio molecular dynamics further confirmed that under applied stress Z(3)-GDYNR exhibits less deformation than A(3)-GDYNR, indicating superior stability. This work provides the necessary theoretical basis for understanding graphene nanoribbons (GDYNRs).

Pnictogen-Rich Heterocycles Derived from a Phosphadiazonium Cation.

Heterocycles that pair main group elements and nitrogen are extremely important within the π-conjugated heterocycles research community. Compared to the vast number of boron-nitrogen heterocycles, those that include phosphorus are less common. Furthermore, the use of phosphorus-nitrogen triple bonds of any type to prepare such compounds is unprecedented. Here, we pair pyridyl hydrazonide ligands with phosphadiazonium cations and demonstrate that the chelated Mes*NP group is directly implicated in the photophysical and redox properties observed for the resulting heterocycles. In doing so, we introduce a novel building block for the production of phosphorus-containing heterocycles that could find use in small molecule activation and catalysis or as the functional component of emerging organic electronics.

A Cascade of Strain-Driven Events Converting Benzynes to Alkynylbenzocyclobutenes to 1,3-Dien-5-ynes to Cyclic Allenes to Benzocyclohexadienones.

Here, we report a strain-promoted cascade reaction that proceeds via multiple strained intermediates, ultimately driven by the high potential energy inherent in alkyne triple bonds (C≡C). More specifically, four alkynes (three from an HDDA benzyne precursor and the fourth from a conjugated enyne reaction partner) are transformed into eight of the skeletal carbons in the benzocyclohexadienone products. The reaction pathway proceeds sequentially via strained benzyne, benzocyclobutene, and cyclic allene intermediates. DFT computations suggest that the slowest step following benzyne generation is the 4π-electrocyclic ring-opening of the alkynylbenzocyclobutene to a 1,3-dien-5-yne (an alkynylxylylene) intermediate. The activation energy for the subsequent 6π-electrocyclic ring-closure is lower than that for related acyclic dienynes because of the aromaticity that is being regained in the transition structure. Finally, the isolation of the benzocyclohexadienone products rather than their phenolic tautomers is notable.

Highly Sensitive Switchable Sensors for Hydroxide on Glass Surfaces Based on Isoquinolinium-Quinolinium-substituted Acetylenes.

Bi-substituted acetylenes with a quinolinium and an isoquinolinium substituent are described, which reversibly form intensely colored adducts with O-nucleophiles and thus enable the detection of >0,5 ppm hydroxide on the surfaces of various glasses. Acids reconstitute the colorless bi-substituted acetylenes. The quinolinium and isoquinolinium rings are bound via their 2-, 3-, 4- and 1-, 3-, 4-positions to the triple bond, respectively. The choice of substitution sites of the hetarenium rings enables the design of mixed conjugated/cross-conjugated π-electron systems. Depending on the combination of binding sites, the frontier orbital profile, the triple bond polarization, the fluorescence behaviour, and the sensitivity to hydroxide differs.

Nitrogen-Rich Molybdenum Nitride Synthesized in a Crucible under Air.

The triple bond in N2 is significantly stronger than the double bond in O2, meaning that synthesizing nitrogen-rich nitrides typically requires activated nitrogen precursors, such as ammonia, plasma-cracked atomic nitrogen, or high-pressure N2. Here, we report a synthesis of nitrogen-rich nitrides under ambient pressure and atmosphere. Using Na2MoO4 and dicyandiamide precursors, we synthesized nitrogen-rich γ-Mo2N3 in an alumina crucible under an ambient atmosphere, heated in a box furnace between 500 and 600 °C. Byproducts of this metathesis reaction include volatile gases and solid Na(OCN), which can be washed away with water. X-ray diffraction and neutron diffraction showed Mo2N3 with a rock salt structure having cation vacancies, with no oxygen incorporation, in contrast to the more common nitrogen-poor rock salt Mo2N with anion vacancies. Moreover, an increase in temperature to 700 °C resulted in molybdenum oxynitride, Mo0.84N0.72O0.27. This work illustrates the potential for dicyandiamide as an ambient-temperature metathesis precursor for an increased effective nitrogen chemical potential under ambient conditions. The classical experimental setting often used for solid-state oxide synthesis, therefore, has the potential to expand the nitride chemistry.

Ru(II)-Catalyzed Deoxygenative Formal [3 + 1 + 2] Benzannulation of Allyl Alcohols and Acetylenediesters via C-H Activation and Selective Carbon-Carbon Triple Bond Cleavage.

An unprecedented Ru(II)-catalyzed deoxygenative, site-selective formal [3 + 1 + 2] benzannulation reaction for the efficient synthesis of highly substituted benzene molecules is reported. This reaction between allyl alcohols and acetylenedicarboxylate esters proceeds via cascade C-H activation, consecutive double migratory insertion with alkynes, and cycloaromatization followed by an unusual specific C-C triple bond cleavage.

Elektrophile Aktivierung von S−Si‐Reagenzien mit Silyliumionen für deren regio‐ und diastereoselektive Addition an C−C‐Mehrfachbindungen

AbstractEs wird eine regioselektive silyliumionvermittelte Thiosilylierung von internen C−C‐Dreifachbindungen mit Kontrolle der Doppelbindungsgeometrie beschrieben. Im Zuge dieser Zweikomponentenreaktion eines Alkins und eines Thiosilans werden sowohl eine C(sp2)−S‐ als auch eine C(sp2)−Si‐Bindung mit einer trans‐Beziehung gebildet. Die hierdurch entstandene orthogonal funktionalisierte C−C‐Doppelbindung lässt sich chemoselektiv defunktionalisieren oder unter Erhalt der Alkenkonfiguration in Kreuzkupplungsreaktionen weiter umsetzen. Die Reaktionsvorschrift ist ebenfalls auf die regio‐ und diastereoselektive Thiosilylierung von terminalen Allenen anwendbar, was zu allylischen Thioethern, die eine Vinylsilaneinheit enthalten, führt. Diese Reaktionen beinhalten die elektrophile Aktivierung des S−Si‐Reagenzes, ein silyliertes Thiophenol und sogar Alkylthiolderivat, durch eine in situ erzeugte Carbokationzwischenstufe. Der Katalysecyclus wird durch ein bissilyliertes Aryl‐ oder Alkylsulfoniumion als ein Shuttle für das kationische Siliciumelektrophil aufrechterhalten. Dessen unabhängige Darstellung und strukturelle Charakterisierung durch Röntgenbeugung werden ebenfalls berichtet.