Frontier molecular orbital contribution analysis (FMO-CA) model is used for determining the regioselectivity of nucleophilic addition to substituted arynes. The nucleophile attacks the carbon ...possessing higher contribution of LUMO.
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•Low cost computational method for predicting the regioselectivity of arynes.•Novel approach based on frontier molecular orbital (FMO) theory.•Reliable approach for altering the selectivity using the substituent effects.
The regioselectivity of nucleophilic addition to substituted arynes was predicted using frontier molecular orbital contribution analysis. This model indicates that the percentage of the LUMO on the reacting terminus of the aryne is responsible for the observed regioselectivity; the nucleophile attacks the carbon possessing higher contribution of the LUMO.
Conjugated Molecular Nanotubes Mirzaei, Saber; Castro, Edison; Hernández Sánchez, Raúl
Chemistry : a European journal,
June 16, 2021, Letnik:
27, Številka:
34
Journal Article
Recenzirano
Molecular compounds with permanent tubular architectures displaying radial π‐conjugation are exceedingly rare. Their radial and axial delocalization presents them with unique optical and electronic ...properties, such as remarkable tuning of their Stokes shifts, and redox switching between global and local aromaticity. Although these tubular compounds display large internal void spaces, these attributes have not been extensively explored, thus presenting future opportunities in the development of materials. By using cutting‐edge synthetic methodologies to bend aromatic surfaces, large opportunities in synthesis, property discovery, and applications are expected in new members of this family of conjugated molecular nanotubes.
Synthetic efforts to bend aromatic surfaces have had a remarkable evolution during the last dozen years. Conjugated nanorings and nanobelts are among the most well‐known examples. However, this progress has also led to the synthesis of molecular compounds with permanent tubular shapes with radial and axial π surfaces, which are the highlight of this Minireview.
A simple model has been developed for predicting the regioselectivity of arynes using orbital electronegativity. Based on this model, the nucleophile attacks the terminus possessing lower orbital ...electronegativity.
We employed the density functionaly theory (DFT)-predicted regioselectivity of the intramolecular Scholl reaction in phenanthrene and dibenzog,pchrysene frameworks to obtain π-extended mono and ...double 7helicenes, respectively. The formation of these helical structures occurs despite the buildup of a large strain energy up to 30 kcal/mol compared with their most stable isomers. The twisted and strained structures were characterized and analyzed by experimental (NMR, UV–vis, emission, electrochemistry, and single-crystal X-ray diffraction) techniques and were further supported by DFT calculations.
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•RGO/Au/PTP NPs /GE was successfully prepared.•The nanocomposite can significantly improve electrochemical performance.•EIS and SWV technics are used to detect H.pylori.•The biosensor ...has a limit of detection (LOD) of 0.0080 μM for impedance and 0.0067 μM for SWV curve.
Electrochemical biosensors are simple cost-efficient tools to determine H.pylori (Hsp60), as responsible for gastric infections. The active surface area and conductivity of the electrode were improved by Reduced Graphene Oxide (RGO) and Gold (Au) nanoparticles, respectively, and the aptamer was conjugated on the polythiophene (PTP)-modified electrode. To confirm the physiochemical properties of the synthesized nanomaterials, X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FTIR), and transmission electron microscopy (TEM) tests have been done. Furthermore, to characterize the modified electrode, cyclic voltammetry (CV), square wave voltammetry (SWV), and electrochemical impedance spectroscopy (EIS) were used and revealed the effect of adding each mentioned nanoparticles (NPs) and different concentrations of Hsp60 on the response of the probe. The linear behavior of the modified electrode against a wide range of concentrations of Hsp60, shows the reliability of the developed biosensor, with a limit of detection (LOD) of 0.0080 μM for impedance and 0.0067 μM for SWV curve. Also, the selectivity test of this electrochemical biosensor demonstrated that its sensitivity to Hsp60 is more than 10 times higher than other biomaterials. These findings show that the proposed nanoprobe could be manifested as a diagnostic system with a wonderful potential to detect and analyze H.pylori.
The intrinsic reactivity of allopurinol oxidation is calculated using the active-site models of aldehyde oxidase and xanthine oxidase (molybdopterin cofactor, MoCo) enzymes. The effects of substrate ...tautomerization, deprotonation and its orientation with respect to the active-site were considered. Among several mechanistic approaches, the most favorable mechanisms are the stepwise pathways. The transition barrier for the most stable tautomer of allopurinol is around 19.83 kcal mol −1 . The stepwise approaches indicate the significant role of glutamate → glutamic acid conversion in the catabolism of allopurinol. Both aldehyde oxidase (AO) and xanthine oxidase (XO) could metabolize the allopurinol to oxypurinol through the self-inhibitory mechanism. This pathway is not in accordance with the experimental results which showed the release of oxypurinol with a low half-life. This phenomenon and also the presence of experimental evidence of allopurinol interaction with cytochrome P450 and drugs which are metabolized with P450 encouraged us to investigate allopurinol oxidation using the active species of P450 enzyme, compound I (Cpd I). The P450 enzymes are responsible for the catabolism of the overwhelming majority of drugs. The detailed understanding of the P450-catalyzed mechanism could result in more precise predictions about the drug metabolism and also the drug–drug interactions. The results of this study reveal that cytochrome P450 can successfully metabolize allopurinol with both a thermodynamically and kinetically feasible mechanism. The rate-determining step of this mechanism is around 22.77 kcal mol −1 . Allopurinol oxidation with P450 will lead to the release of oxypurinol, not a self-inhibitory mechanism. The outcomes of this investigation can be extended to the other purine or pyrimidine containing compounds (especially hypoxanthine) which are metabolized by this group of enzymes.
We employed density functional theory (DFT) methods to investigate the most plausible mechanism of cyclization/ring expansion of proline with o-alkynylbenzaldehyde. This one-pot reaction starts with ...the in situ formation of azomethine ylide, which can undergo three different reaction pathways to form the final product. Two mechanisms are based on nucleophilic addition and 4π-electrocyclization of the azomethine ylide, and our results indicate that the rate-determining step (RDS) of these two cyclizations are 40.1 and 40.2 kcal/mol, respectively. The third novel pathway relies upon 8π-electrocyclization as the key step of this reaction; interestingly, the RDS of this cyclization is ∼20.6 kcal/mol, which shows this route to be most feasible. Thus, we introduce a novel mechanism for the electrocyclization reaction of conjugated azomethine ylides that can help chemists to design and access a new series of compounds.
In this study, a metal‐phosphate layered/activated carbon (KMSP@AC) composed of potassium (K), manganese (Mn), tin (Sn) and phosphorous (P) was prepared by the solvothermal method. The proposed ...nanocomposite was used as an effective adsorbent to remove Cd(II), Co(II), Ni(II), Pb(II) and V(III) from water samples in oil‐rich areas prior to ICP‐OES analysis. The KMSP@AC was fully characterized using FTIR, SEM and EDX. Factors influencing the removal process (pH, adsorbent dosage, initial concentration and contact time) were studied and optimized. The experimental process was evaluated with kinetic and isotherm models. The adsorption isotherm investigation showed that the adsorption followed the monolayer Langmuir isotherm model with the maximum adsorption capacities of 25 mg/g (Cd2+), 31 mg/g (Co2+), 49 mg/g (Ni3+), 91 mg/g (Pb2+) and 141 mg/g (V3+). The kinetic studies indicated that the pseudo‐second‐order model is well‐fitted to the process with an appropriate correlation coefficient (R2 > 0.99) at an equilibrium time of 120 min. The adsorption of metal ions on the surface of the adsorbent was mainly a physisorption process through electrostatic interactions.
The efficiency of bicarbonate molecule (HCO3−) as a proton shuttle in the tautomerization and (non)enzymatic CO2 hydration reactions has been investigated with the aid of computational chemistry ...methods (DFT and ab initio). The results revealed that bicarbonate can decrease the barrier height of tautomerization (keto-enol, azo-hydrazo and imine-amine) more than 70%. This value is around 45% for water molecules. Also, HCO3− can catalyze the CO2 hydration both inside (enzymatic) and outside (nonenzymatic) the active site of human carbonic anhydrases II (HCA II). In the absence of enzyme, bicarbonate molecule can lower the CO2 hydration from ∼50 kcal mol−1 in the gas phase to ∼14 kcal mol−1 in the aqueous media. This reaction maintains its barrier (∼15 kcal mol−1) for bicarbonate-Zn complex in the active site of enzyme; it has been observed that amino acid residues, mainly Thr199 and Glu106, are actively involved in the proton transfer network and facilitate CO2 hydration ability of bicarbonate.
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•New function for bicarbonate molecule in the physiological condition.•High proton shuttle efficiency of bicarbonate vs. water in tautomerization reactions.•Performance of bicarbonate for catalyzing CO2 hydration reaction.
