DFT Calculations Research Articles

(5+1)−1] Cyclization of Nitroepoxides to Pyridinium 1,4‐Zwitterionic Thiolates for the Synthesis of Indolizine Derivatives

AbstractThe synthesis of indolizine derivatives was achieved through the reaction of pyridinium 1,4‐zwitterionic thiolates with a diverse array of 2‐methyl‐2‐nitro‐3‐aryloxiranes. Subsequent investigations unveiled a synthetic route to indolizines via a stepwise [(5+1)−1] pathway, with unstable pyridothiazines serving as transient intermediates. DFT calculations elucidated that this transformation entails sequential annulation, deacylation, desulfurization, and oxidation steps.

Production of Branched Alkanes by Upcycling of Waste Polyethylene over Controlled Acid Sites of SO4/ZrO2-Al2O3 Catalyst.

Branched alkanes, which enhance the octane number of gasoline, can be produced from waste polyethylene. However, achieving highly selective production of branched alkanes presents a significant challenge in the upcycling of waste polyethylene, and the maximum selectivity for branched alkanes reported up to date is about 70%. Here, we report a one-pot process to convert polyethylene into gasoline-range hydrocarbons (C4-C13) with yield of 73.3% over SO42-ZrO2-Al2O3 catalyst at 280 °C. The proportion of branched alkanes reaches 90.1% within the C4-C13 fraction. Incorporation of sulfate group endows the catalyst with strong Lewis acid sites and weak and moderate Brønsted acid sites. In situ X-ray absorption, in situ infrared spectroscopy, in situ small angle neutron scattering, and DFT calculations reveal that polyethylene activation occurs through the synergy between sulfate groups and strong Lewis acid sites (Zr sites). The weak and moderate Brønsted acid sites preferentially catalyze the isomerization and type A β-scission processes, which favors the formation of branched alkanes, while suppressing competing reactions that produce straight-chain alkanes.

Production of Branched Alkanes by Upcycling of Waste Polyethylene over Controlled Acid Sites of SO4/ZrO2‐Al2O3 Catalyst

Branched alkanes, which enhance the octane number of gasoline, can be produced from waste polyethylene. However, achieving highly selective production of branched alkanes presents a significant challenge in the upcycling of waste polyethylene, and the maximum selectivity for branched alkanes reported up to date is about 70%. Here, we report a one‐pot process to convert polyethylene into gasoline‐range hydrocarbons (C4‐C13) with yield of 73.3% over SO42‐ZrO2‐Al2O3 catalyst at 280 °C. The proportion of branched alkanes reaches 90.1% within the C4‐C13 fraction. Incorporation of sulfate group endows the catalyst with strong Lewis acid sites and weak and moderate Brønsted acid sites. In situ X‐ray absorption, in situ infrared spectroscopy, in situ small angle neutron scattering, and DFT calculations reveal that polyethylene activation occurs through the synergy between sulfate groups and strong Lewis acid sites (Zr sites). The weak and moderate Brønsted acid sites preferentially catalyze the isomerization and type A β‐scission processes, which favors the formation of branched alkanes, while suppressing competing reactions that produce straight‐chain alkanes.

Selective Access to 2‐Phenylquinazolin‐4(3H)‐Ones and 2,3‐Dihydroquinazolin‐4(1H)‐Ones from Same Precursors in Organic Salts Derived DES

AbstractA binary mixture of organic salts, also known as ionic liquids, [C12mim][Br]:[MPIM][HCOO] denoted as BmIL1 has been explored as bifunctional catalyst for the selective synthesis of 2‐phenylquinazolin‐4(3H)‐ones and 2,3‐dihydroquinazolin‐(1H)‐ones from same precursors under metal, ligand and additive free conditions. The methodology has been extended to the synthesis of 2‐phenylquinazolin‐4(3H)‐ones via another pathway from different precursors under the same catalytic system. Greener synthesis of existing drugs reestablished the multifunctionality of BmIL1. Gram scale synthesis of both the products, DFT calculations and sc‐XRD data add significance to the developed protocol. Moreover, high atom economy and eco score values justify the sustainability of the methodology.

Silver Nanoparticle‐Embedded Zirconium‐Based Metal‐Organic Framework for Photoreduction of Carbon Dioxide to Acetic Acid in Aqueous Medium

AbstractCatalytic conversion of CO2 into value‐added chemicals is necessary to mitigate the increasing global warming and energy‐related issues. The selective production of C2 or C2+ products by photoreduction of CO2 is a challenging task due to the sluggish kinetics of C─C coupling. Herein, the potential of a silver nanoparticle (Ag NP) incorporated metal‐organic framework (MOF), NU‐1000 is introduced, to harvest light and ease the uphill electron transfer. The growth of silver nanoparticles on thiol‐functionalized NU‐1000 is studied using the atomic pair distribution function (PDF) analysis. The C2 product formed using Ag@NU‐1000‐SH without any sacrificial agents is acetic acid, which is confirmed by 1H‐NMR and HRMS data. The catalyst displays a high acetate output of 293.58 µmolg−1h−1 with a selectivity of 79.4%. The XPS and DFT calculations evidence that the presence of the charge‐polarised states in the as‐synthesized catalyst act as asymmetric centers that favor the C─C coupling reaction. The combined experimental (in situ DRIFT spectroscopic studies) and theoretical calculations reveal that the C─C coupling takes place via the coupling of COOH*intermediates.

Enhancing the Chemical Stability of P12L24 Cage: Transformation of the Chemically Labile Imine Cage into a Robust Carbamate Cage.

Herein, we report enhancement in chemical stability of the imine-based porphyrinic cage P12L24 by converting it into a robust carbamate porphyrinic cage, c-P12L24, through a two-step post-synthetic modification process. First, the imine bonds in P12L24 were reduced to form an amine-based cage, r-P12L24, followed by carbamation using N,N'-carbonyldiimidazole (CDI) to yield c-P12L24. The resulting carbamate cage exhibits high stability under acidic and basic conditions (pH 1-13) and in the presence of moisture. 1H NMR, DOSY NMR, and DFT calculations revealed that reducing the imine bonds to amine increases the framework's flexibility, causing partial structural collapse, whereas the carbamate formation restores structural rigidity. The insertion of a 4.0 nm molecular ruler into the cavity of zinc-metallated c-P12L24 via metal-ligand coordination further confirmed restoration of the cavity size and geometry of the original cage. This enhancement of chemical stability through carbamate formation can pave the way to a wide range of potential applications for the gigantic porphyrinic cage.

Evaluating and improving the predictive accuracy of mixing enthalpies and volumes in disordered alloys from universal pretrained machine learning potentials

The advent of machine learning in materials science opens the way for exciting and ambitious simulations of large systems and long time scales with the accuracy of calculations. Recently, several pretrained universal machine learned interatomic potentials (UPMLIPs) have been published, i.e., potentials distributed with a single set of weights trained to target systems across a very wide range of chemistries and atomic arrangements. These potentials raise the hope of reducing the computational cost and methodological complexity of performing simulations compared to models that require for-purpose training. However, the application of these models needs critical evaluation to assess their usability across material types and properties. In this work, we investigate the application of the following UPMLIPs: MACE, CHGNET, and M3GNET to the context of alloy theory. We calculate the mixing enthalpies and volumes of 21 binary alloy systems and compare the results with DFT calculations to assess the performance of these potentials over different properties and types of materials. We find that the small relative energies necessary to correctly predict mixing energies are generally not reproduced by these methods with sufficient accuracy to describe correct mixing behaviors. However, the performance can be significantly improved by supplementing the training data with relevant training data. The potentials can also be used to partially accelerate these calculations by replacing the structural relaxation step. Published by the American Physical Society 2024

Unravelling the structure of one-electron oxidation products of model peptide backbones containing methionine by IRMPD spectroscopy: the effect of the neighbouring groups.

A series of Methionine (Met) derivatives, where either the amino group and/or the carboxylic acid group is blocked by acetyl and/or methyl ester functionalities, has been investigated by Collision Induced Dissociation-tandem mass spectrometry (CID-MS2) and Infrared Multiple Photon Dissociation (IRMPD) spectroscopy. The CID-MS2 experiments were performed using a Fourier-transform ion-cyclotron-resonance (FT-ICR) mass spectrometer equipped with an electrospray ionization (ESI) source. The IRMPD spectra were recorded employing a Paul type ion-trap coupled with the free-electron laser (FEL) FELIX in the fingerprint region from 600 to 2000 cm-1. We show that the oxidation of the methionine residue with protected terminal groups induces the formation of a sulfoxide group. However, compared to the IRMPD spectrum of protonated methionine and methionine sulfoxide, significant spectral differences are observed in the spectra of model peptide backbones containing methionine. DFT calculations show that protonation occurs on the sulfoxide group in the gas phase for these model peptide backbones containing methionine, shifting the diagnostic signature of the sulfoxide group from 1000 to 862 cm-1.

Carbazolyl-Decorated Metal-Organic Framework with a High Fluorescent Quantum Yield for Detection and Photocatalytic Degradation of Organic Contaminants.

A carbazolyl-based fluorescent metal-organic framework with deep-blue light emission and a high quantum yield (88%) has been screened out by changing the ratio of mixed ligands, named Cz-MOF-2, which was constructed by ZrO4(OH)4 clusters, 3-(9-ethyl-9H-carbazol-3-yl)-4-methylthieno[2,3-b]thiophene-2,5-dicarboxylate (H2ECMTDC) and 3,4-dimethyl-dihydrothieno[2,3-b]thiophene-2,5-dicarboxylate (H2DMTDC). Cz-MOF-2 has excellent sensitivity in fluorescent sensing of 2,6-dichloro-4-nitroaniline (DCN), nitrofurazone (NZF), and nitrofurantoin (NFT) with detection limits of 3.37 × 10-7, 1.64 × 10-5, and 1.76 × 10-5 M, respectively. The quenching mechanisms involving electron transfer and competitive absorption were comprehensively elucidated through DFT calculations and UV absorption experiments. Cz-MOF-2 has been fabricated into a rapidly regenerated composite membrane with PVDF as a visualized fluorescent sensor for DCN. Furthermore, the carbazolyl groups covalently modified in the framework endowed Cz-MOF-2 with a suitable band gap (2.58 eV) for photocatalytic degradation of organic contaminants. It demonstrated superior photocatalytic efficiency compared to UiO-66 and NH2-UiO-66 in the degradation of tetracycline (TC), and the removal efficiency was up to 85% (20 mg of catalyst, 50 mL, 20 mg/L TC solution and 180 min) under simulated sunlight irradiation using a 300 W Xe lamp. Photoelectrochemical tests demonstrate that Cz-MOF-2 exhibits high photocurrent density and low charge transfer resistance, which provide evidence for the efficient charge separation capability. Radical trapping experiments and ESR detection have substantiated that ·O2- and h+ are the primary active species involved in this photocatalytic reaction. This work highlights the potential of MOFs in the targeted design and development of fluorescent sensors and photocatalysts for environmental detection and remediation.

Cycloaddition of Butadiene with Perfluoroethylene: Prediction of a Periselectivity Switch under Pressure.

Defying the common Diels-Alder reactivity, the thermal cycloaddition between butadiene and tetrafluoroethylene (TFE) yields exclusively a [2 + 2] cycloadduct via a stepwise diradical mechanism. Here, we study the possibility of reverting to the normal [4 + 2] reactivity in this reaction under high pressure. DFT calculations using the eXtreme Pressure Polarizable Continuum Model (XP-PCM) suggest a more negative activation volume for the concerted [4 + 2] mechanism than the stepwise [2 + 2] mechanism and predict a switch in periselectivity at 1.4 gigapascal (GPa).

Unlocking the Effects of the RuCo Alloy Ratio on Alkaline Hydrogen Production.

Understanding the interaction between Ru and Co components and the alloy ratio effects on the catalytic process is a technical challenge that requires a precise alloy structural design. This study proposes an effective stepwise annealing method for the construction of RuCo alloy-based electrocatalysts with varied Ru:Co ratios. Interestingly, as the concentration of Co in the first-step pyrolysis products increases, the secondary pyrolysis results in RuCo composites undergoing a transition from incomplete alloying to alloy ratios of 1:1, 1:2, and 1:8. When the alloy ratio is 1:1, more Run+ and Co0 transform into Ru0 and Co2/3+. In 1 M KOH, RuCo-0.6/NC demonstrates outstanding catalytic performance and durability even superior to that of commercial Pt/C, delivering a lower overpotential of 16 mV at 10 mA cm-2. DFT calculations reveal that the fast H2O dissociation and moderate H adsorption guarantee the superior activity of RuCo.

Modulating the Competition between Different Atoms to Form Halogen Bonds.

I and Br atoms are placed on opposite ends of a n-butyl group, with each allowed to form a halogen bond (XB) with NH3. DFT calculations show that the intrinsic preference of the nucleophile for the heavier I over Br can be reversed by the proper placement of substituents on the alkyl chain. A similar reversal occurs for NH2 and OH groups on the alkyl chain, where substituents make the O a better electron donor than N in an XB to an electrophilic ICCH. The highly mobile π-electron cloud of an aromatic ring makes such reversals much more difficult when the pair of competing atoms are placed on, or within, such a ring.

What Can Chemical Bonding Tell Us about Photoinduced Phase Transition Reactions in Inorganic Semiconductors? Insight from Bismuth-Antimony Selenide.

Photoreactive self-healing semiconductors with suitable bandgaps for solar energy conversion offer an intriguing path to making resilient and low-cost photovoltaic devices through the introduction of a self-recovery path. However, only a few inorganic photovoltaic materials have such quality, and the underlying chemical properties that enable it are unknown, which poses a significant limit to our ability to study and discover new self-healing semiconductors. Recently, we have found that antimony trichalcogenide (Sb2Se3 and Sb2S3) and chalcohalides (e.g., SbSeI) can undergo a reversible photoinduced phase transition (PIPT) in which the structure is restored after photoinduced damage incurs to the materials. This group of materials offer a unique opportunity for studying PIPT and its limits. In particular, this group of materials facilitate the study of functional permutation to specific crystalline sites and to finding the limits of PIPT occurrence, which sheds light on the origin of the PIPT and self-recovery of this class of materials. Using Raman spectroscopy of thin films, and following signature vibrations of transition species, we have found that the PIPT magnitude decays upon gradual BiSb(1) substitution in a Sb2-xBixSe3 homologous series, until nearly one in five Sb ions is substituted with Bi. Then, the PIPT diminishes completely. The homologous series occurs along a transition from covalent to metavalent chemical bonding. By expanding our search, we find that a correlation between bonding type and photoreactivity does exist but conclude that it is an insufficient condition. Instead, we suggest, based on bond order and additional DFT calculations, that sufficient bonding states at the bottom of the conduction band are also required. This joint experimental and computational study pushes the limits of designing self-healing inorganic semiconductors for various applications and provides tools for further expansion.

Gold(I)‐Catalyzed Regioselective Cycloisomerization of Bis(indol‐3‐yl)‐ynamides to Access Five‐membered Ring Linked Bisindole Derivatives

A gold(I)‐catalyzed regioselective cycloisomerization of bis(indol‐3‐yl)‐ynamides for the rapid construction of five‐membered ring linked bisindole derivatives has been reported, affording the desired products in the range of 72% ‐ 94% yields under mild conditions along with broad substrate scope. Moreover, DFT calculation of the NBO (natural bond orbital) charge supports the origin of its regioselectivity.

Elaboration of newly synthesized tetrahydrobenzo[b]thiophene derivatives and exploring their antioxidant evaluation, molecular docking, and DFT studies

Herein, 2-amino-6-(tert-butyl)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile (1) was synthesized in excellent yield through gewald reaction in multi components one pot reaction. Compound 1 was utilized as a building block to synthesize a new group of tetrahydro benzo[b] thiophene congeners. The chemical structure of all the novel tetrahydro benzo[b]thiophene derivatives were elucidated through the melting point, elemental analysis, FT-IR, 1H-NMR, and mass spectroscopy. Furthermore, the total antioxidant capacity (TAC) of all the newly synthesized heterocyclic derivatives was evaluated according to the phosphomolybdenum method using ascorbic acid as standard. The findings revealed that compounds 1, 16, and 17 demonstrated significant antioxidant potency comparable to that of ascorbic acid. This suggests the potential of these heterocycles as promising candidates for antioxidant drugs in the treatment of oxidative stress-related diseases. Finally, molecular docking was conducted to study the binding affinity for the most potent antioxidant compounds 1, 16, 17 and ascorbic acid inside the interactions of compounds 1, 16, and 17 with the Keap1 (Kelch-like ECH-associated protein 1) protein (PDB: 7C5E), compared to the co-crystallized ligand triethylene glycol (PGE) and ascorbic acid as a reference drug for antioxidants. DFT calculations and global descriptors were calculated for the most potent compounds to correlate the relation between chemical structure and reactivity.

Highly efficient CoAl-LDH/(110) facet-exposed BiOBr catalysts: Promotional effect of Z-type heterojunction and oxygen vacancies in photocatalytic ciprofloxacin degradation

Photocatalysis has received extensive attention as a sustainable technology. Herein, a 2D/2D CoAl-LDH/(110) facet-exposed BiOBr Z-type heterojunction photocatalyst enriched with oxygen vacancies (OVs) and Lewis acid sites was prepared by deposition-precipitation method. Results show that the removal of ciprofloxacin by the optimal heterojunction achieves 88 % within 10 min and 98.6 % within 95 min under visible light. Characterization and DFT calculation reveal that CoAl-LDH induces high-energy (110) crystal plane exposure of BiOBr, resulting in the generation of surface OVs and Lewis acid sites. OVs contribute to the adsorption of dissolved oxygen in water, thereby facilitating the generation of •O2−. And Bi(3−x)+ Lewis acid sites promote the adsorption and degradation of reactant molecules. The charge transfer recombination mechanism of the heterojunction enhances the utilization of photogenerated electrons and holes, improving the catalyst photostability. This work provides a simple method for constructing efficient and stable Z-type heterojunctions with defects for photocatalytic water treatment.

Frustrated Radical Pairs: From Fleeting Intermediates to Isolable Species.

We present the design and comprehensive investigation of stable para-substituted triarylamine-2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) radical ion pairs (RIPs) generated via single-electron transfer (SET). We quantified the degree of SET in both solution and solid phases, utilising a suite of spectroscopic techniques including IR, EPR, NMR, and single-crystal X-ray diffraction (SC-XRD). Our findings reveal that the extent of SET is significantly influenced by the nature of the substituents (MeO > tBu > Br) and the polarity of the solvent (MeCN > DCM > toluene). The radical ion pair [(pMeOPh)3N]•+[DDQ]•- was unambiguously identified using EPR and UV-vis spectroscopy, and its structure was confirmed by SC-XRD. Detailed analysis indicates an open-shell singlet ground state with a thermally accessible triplet state, as corroborated by EPR, magnetic susceptibility measurements, and DFT calculations. This study offers crucial insights into the mechanistic pathways of RIP formation and tuning both in solution and solid states, laying the groundwork for future exploration of their reactivity and potential applications.

Structural and Photophysical Differences in Crystalline Trigonal Planar Copper Iodide Complexes with 1,2-Bis(methylpyridin-2-yl)disilane Ligands.

We synthesized trigonal planar Cu(I) iodide complexes with 1,2-bis(methylpyridin-2-yl)disilane ligands L1-L4 and investigated how the substitution position of the methyl group on the pyridine ring in σ-π conjugation affects their structure and physical properties. The structures were characterized by NMR, elemental analysis, and single-crystal X-ray diffraction. In the crystalline state, the methylpyridyl groups of CuIL1-CuIL3 were coordinated with Cu(I) in an anticlinal conformation relative to the Si-Si σ bond, whereas those of CuIL4 were coordinated with Cu(I) in a synperiplanar conformation relative to the Si-Si σ bond. The conformational difference in the crystalline state was influenced by the N-Cu-N bite angle and the emission wavelength. CuIL1-CuIL3 exhibited blue-green emission (λem: 476-494 nm), and CuIL4 exhibited green-yellow emission (λem: 512 nm) with high emission quantum yields (Φ: 0.59-0.86) in the crystalline state at 293 K. These Cu(I) complexes exhibited thermally activated delayed fluorescence from the S1 state at 293 K and phosphorescence from the T1 state at 77 K in the crystalline state. The optical properties in the crystalline state were discussed by DFT and TD-DFT calculations. These complexes also displayed aggregation-induced emission in THF-water solution (fw > 80%), although they did not show emission in dehydrated THF.

Stable Mono‐radical and Triplet Diradicals Based on Allylic Radical‐Embedded All‐benzenoid Polycyclic Hydrocarbons

High‐spin organic radicals are notable for their unique optical, electronic, and magnetic properties, but synthesizing stable high‐spin systems is challenging due to their inherent reactivity. This study presents a novel strategy for designing stable high‐spin polycyclic hydrocarbons (PHs) by incorporating allylic radical into fused aromatic benzenoid rings. To enhance stability, large steric hindrance groups with a synergistic captodative effect were added to the allylic radical centers. This approach was applied to synthesize derivatives of two open‐shell all‐benzenoid PHs: benzo[fg]tetracene (1) and dibenzo[fg,lm]heptacene (2). Both compounds exhibited excellent stability, with diradical 2 showing a half‐life of up to 17.2 days under ambient conditions. Bond length analysis and theoretical calculations suggest that 1 and 2 predominantly feature Clar’s aromatic sextet structures with embedded allylic radicals. Compound 2 was confirmed to have a triplet ground state through DFT calculations and experimental methods, including pulse EPR spectroscopy and SQUID measurements. This work introduces a new design strategy for stable high‐spin hydrocarbons, paving the way for future developments in high‐spin organic materials.

Predicting Elastic and Electronic Properties of Quaternary Heusler Alloys Using Machine Learning and DFT Calculations

Predicting Elastic and Electronic Properties of Quaternary Heusler Alloys Using Machine Learning and DFT Calculations