Synthesis, characterization, and structure computational calculations of the oxycalcogenide LaCuOSe for thermoelectric applications

A series of pure and doped TiO2 nanomaterials with different Zr4+ ions content have been synthesized by the simple sol-gel method. Both types of materials (nanopowders and nanofilms scratched off of the working electrode’s surface) have been characterized in detail by XRD, TEM, and Raman techniques. Inserting dopant ions into the TiO2 structure has resulted in inhibition of crystal growth and prevention of phase transformation. The role of Zr4+ ions in this process was explained by performing computer simulations. The three structures such as pure anatase, Zr-doped TiO2, and tetragonal ZrO2 have been investigated using density functional theory extended by Hubbard correction. The computational calculations correlate well with experimental results. Formation of defects and broadening of energy bandgap in defected Zr-doped materials have been confirmed. It turned out that the oxygen vacancies with substituting Zr4+ ions in TiO2 structure have a positive influence on the performance of dye-sensitized solar cells. The overall photoconversion efficiency enhancement up to 8.63% by introducing 3.7% Zr4+ ions into the TiO2 has been confirmed by I-V curves, EIS, and IPCE measurements. Such efficiency of DSSC utilizing the working electrode made by Zr4+ ions substituted into TiO2 material lattice has been for the first time reported.

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Experimental and Computational Evaluation of Chloranilic Acid as an Universal Chromogenic Reagent for the Development of a Novel 96-Microwell Spectrophotometric Assay for Tyrosine Kinase Inhibitors

Molecules ◽

10.3390/molecules26030744 ◽

2021 ◽

Vol 26 (3) ◽

pp. 744

Author(s):

Ibrahim A. Darwish ◽

Hany W. Darwish ◽

Nasr Y. Khalil ◽

Ahmed Y. A. Sayed

Keyword(s):

Tyrosine Kinase ◽

Tyrosine Kinase Inhibitors ◽

Kinase Inhibitors ◽

Spectrophotometric Assay ◽

Charge Transfer Complexes ◽

Physical Parameters ◽

Chloranilic Acid ◽

Chromogenic Reagent ◽

Computational Evaluation ◽

Computational Calculations

The tyrosine kinase inhibitors (TKIs) are chemotherapeutic drugs used for the targeted therapy of various types of cancer. This work discusses the experimental and computational evaluation of chloranilic acid (CLA) as a universal chromogenic reagent for developing a novel 96-microwell spectrophotometric assay (MW-SPA) for TKIs. The reaction resulted in an instantaneous formation of intensely purple colored products with TKIs. Spectrophotometric results confirmed that the reactions proceeded via the formation of charge-transfer complexes (CTCs). The physical parameters were determined for the CTCs of all TKIs. Computational calculations and molecular modelling for the CTCs were conducted, and the site(s) of interaction on each TKI molecule were determined. Under the optimized conditions, Beer’s law correlating the absorbances of the CTCs with the concentrations of TKIs were obeyed in the range of 10–500 µg/well with good correlation coefficients (0.9993–0.9998). The proposed MW-SPA fully validated and successfully applied for the determination of all TKIs in their bulk forms and pharmaceutical formulations (tablets). The proposed MW-SPA is the first assay that can analyze all the TKIs on a single assay system without modifications in the detection wavelength. The advantages of the proposed MW-SPA are simple, economic and, more importantly, have high throughput.

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From Reduction to Oxidation: pH Controlled Reaction of 1 Hydroxyethyl Radical with Caffeic Acid Analogues.

Current Physical Chemistry ◽

10.2174/1877946811666210509032002 ◽

2021 ◽

Vol 11 ◽

Author(s):

Laboni Das ◽

Shashi P Shukla ◽

Suchandra Chatterjee ◽

Ashis K Satpati ◽

Soumyakanti Adhikari

Keyword(s):

Caffeic Acid ◽

Rate Constant ◽

Reduction Process ◽

Phenoxyl Radical ◽

Alpha Tocopherol ◽

Side Chain ◽

Product Analysis ◽

Bimolecular Rate Constant ◽

Ethyl Radical ◽

Computational Calculations

Aims: The aim is to search for newer and better antioxidants through kinetic spectroscopic studies in combination with product analysis and computation. Background: Antioxidant effect of caffeic acid, its derivative, and analogues have been well reported. The antioxidative efficiencies are related to their molecular structure, and two reaction pathways are well accepted, H-atom transfer (HAT) or single electron transfer. 1-hydroxy ethyl radical (1-HER) being an ethanol-derived free radical might be causing the onset of liver injury detected after alcohol administration. 1-HER has also been reported to react with fatty acids and endogenous antioxidants such as glutathione, ascorbic acid, and alpha-tocopherol Objective: The present study is an attempt to understand the reaction mechanism of 1-HER with caffeic acid, its derivative, and analogues in detail. Method: Pulse radiolysis with kinetic absorption spectroscopy has been employed to follow the reaction pathway and identify the intermediates produced in the reaction. The reaction products have been detected using LCMS/MS. Based on these studies, a consolidated mechanism has been proposed. Cyclic voltammetry measurements and computational calculations have been used in support of the proposed mechanism. Result: In the reaction of 1-hydroxy ethyl radical (1-HER) with caffeic acid and its oligomers, reduction takes place below the pKa1, while oxidation occurs with the deprotonated phenolic moiety. The reduction of caffeic acid generates a carbon-centered radical at the double bond of the side chain with a bimolecular rate constant of 1.5x1010 dm3 mol-1 s-1. Notably, a low concentration of oxygen was able to regenerate a part of the caffeic acid molecules in the reduction process. At pH 10 a phenoxyl radical is formed due to oxidation with a much lower bimolecular rate constant (4.2x108 dm3 mol-1 s-1). In the case of di-hydrocaffeic acid, only phenoxyl radical is formed at pH 10 and, no reaction could be observed below pH 8. Conclusion: Change in reactive pattern from reduction to oxidation with change in pH within the same set of reactants has been evidently established in the present study. The results point towards the importance of  unsaturation in the side chain of caffeic acid oligomers for their reaction with 1-HER at neutral pH. The effect of oxygen concentration on the antioxidative protection offered by this class of molecules might be intriguing for the quest of the effectiveness of antioxidants at low concentrations. Other: It may be inferred that the effect of pH on the reactivity pattern as observed is not 1-HER, but substrate-specific, in the present case, phenolic acids. This study generates further scope for in-depth studies on other polyphenols where unsaturation exists in the side chain.

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Tetramer Compound of Manganese Ions with Mixed Valence [MnII MnIII MnIV] and Its Spatial, Electronic, Magnetic, and Theoretical Studies

Crystals ◽

10.3390/cryst8120447 ◽

2018 ◽

Vol 8 (12) ◽

pp. 447 ◽

Cited By ~ 2

Author(s):

Cándida Pastor-Ramírez ◽

Rafael Ulloa ◽

Daniel Ramírez-Rosales ◽

Hugo Vázquez-Lima ◽

Samuel Hernández-Anzaldo ◽

...

Keyword(s):

Mixed Valence ◽

Magnetic Behavior ◽

Local Geometry ◽

Spectroscopic Techniques ◽

Theoretical Studies ◽

The Novel ◽

Manganese Ions ◽

Computational Calculations ◽

Valence Electrons ◽

Coordination Reaction

Using different spectroscopic techniques and computational calculations, we describe the structural and electromagnetic relationship that causes many interesting phenomena within a novel coordination compound with mixed valence manganese (II, III and IV) in its crystal and powder state. The novel compound [MnII MnIII MnIV(HL)2(H2L)2(H2O)4](NO3)2(H2O) 1 was obtained with the Schiff base (E)-2-((2-hydroxybenzylidene)amine)-2-(hydroximethyl)propane-1,3-diol, (H4L), and Mn(NO3)2.4H2O. The coordination reaction was promoted by the deprotonation of the ligand by the soft base triethylamine. The paper’s main contribution is the integration of the experimental and computational studies to explain the interesting magnetic behavior that the mixed valence manganese multimetallic core shows. The results presented herein, which are rarely found for Mn(II), (III) and (IV) complexes, will contribute to the understanding of the magnetic communication generated by the valence electrons and its repercussion in the local geometry and in the overall crystalline structure.

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Experimental and computational kinetics investigations for the reactions of Cl atoms with series of unsaturated ketones in gas phase

10.5194/acp-2017-163 ◽

2017 ◽

Author(s):

Siripina Vijayakumar ◽

Avinash Kumar ◽

Balla Rajakuma

Keyword(s):

Gas Phase ◽

State Theory ◽

Rate Coefficients ◽

Gas Phase Reactions ◽

Temperature Dependent ◽

Unsaturated Ketones ◽

Temperature Range ◽

Computational Calculations ◽

Temperature Rate ◽

Cl Atoms

Abstract. Temperature dependent rate coefficients for the gas phase reactions of Cl atoms with 4-hexen-3-one and 5-hexen-2-one were measured over the temperature range of 298–363 K relative to 1-pentene, 1,3-butadiene and isoprene. Gas Chromatography (GC) was used to measure the concentrations of the organics. The derived temperature dependent Arrhenius expressions are k4-hexen-3-one+Cl (298–363 K) = (2.82 ± 1.76)×10−12exp [(1556 ± 438)/T] cm3 molecule−1 s−1 and k5-hexen-2-one+Cl (298–363 K) = (4.6 ± 2.4)×10−11exp[(646 ± 171)/T] cm3 molecule−1 s−1. The corresponding room temperature rate coefficients are (5.54 ± 0.41)×10−10 cm3 molecule−1 s−1 and (4.00 ± 0.37)×10−10 cm3 molecule−1 s−1 for the reactions of Cl atoms with 4-hexen-3-one and 5-hexen-2-one respectively. To understand the mechanism of Cl atom reactions with unsaturated ketones, computational calculations were performed for the reactions of Cl atoms with 4-hexen-3-one, 5-hexen-2-one and 3-penten-2-one over the temperature range of 275–400 K using Canonical Variational Transition state theory (CVT) with Small Curvature Tunneling (SCT) in combination with CCSD(T)/6-31+G(d, p)//MP2/6-311++G(d, p) level of theory. Atmospheric implications, reaction mechanism and feasibility of the title reactions are discussed in this manuscript.

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DABCO-promoted photocatalytic C–H functionalization of aldehydes

Beilstein Journal of Organic Chemistry ◽

10.3762/bjoc.17.205 ◽

2021 ◽

Vol 17 ◽

pp. 2959-2967

Author(s):

Bruno Maia da Silva Santos ◽

Mariana dos Santos Dupim ◽

Cauê Paula de Souza ◽

Thiago Messias Cardozo ◽

Fernanda Gadini Finelli

Keyword(s):

Hydrogen Atom ◽

Cross Coupling ◽

Hydrogen Atom Transfer ◽

Direct Application ◽

Atom Transfer ◽

Organic Base ◽

Aryl Bromides ◽

Computational Calculations ◽

Acyl Radicals ◽

Aryl Ketones

Herein we present a direct application of DABCO, an inexpensive and broadly accessible organic base, as a hydrogen atom transfer (HAT) abstractor in a photocatalytic strategy for aldehyde C–H activation. The acyl radicals generated in this step were arylated with aryl bromides through a well stablished nickel cross-coupling methodology, leading to a variety of interesting aryl ketones in good yields. We also performed computational calculations to shine light in the HAT step energetics and determined an optimized geometry for the transition state, showing that the hydrogen atom transfer between aldehydes and DABCO is a mildly endergonic, yet sufficiently fast step. The same calculations were performed with quinuclidine, for comparison of both catalysts and the differences are discussed.

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Insights into the Mechanism of Ethionamide Resistance in Mycobacterium tuberculosis through an in silico Structural Evaluation of EthA and Mutants Identified in Clinical Isolates

10.20944/preprints202003.0470.v1 ◽

2020 ◽

Author(s):

Vinicius Carius de Souza ◽

Deborah Antunes ◽

Luciana H.S. Santos ◽

Priscila Vanessa Zabala Capriles Goliatt ◽

Ernesto Raul Caffarena ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Comparative Modeling ◽

Clinical Isolates ◽

Free Energies ◽

Wild Type ◽

Structural Evaluation ◽

Type Complex ◽

Computational Calculations ◽

First Results ◽

Delta G

Mutation in the ethionamide (ETH) activating enzyme, EthA, is the main factor determining resistance to this drug, used to treat TB patients infected with MDR and XDR Mycobacterium tuberculosis isolates. Many mutations in EthA of ETH resistant (ETH-R) isolates have been described but their roles in resistance remain uncharacterized, partly because structural studies on the enzyme are lacking. Thus, we took a two-tier approach to evaluate two mutations (Y50C and T453I) found in ETH-R clinical isolates. First, we used a combination of comparative modeling, molecular docking, and molecular dynamics to build an EthA model in complex with ETH that has hallmark features of structurally characterized homologs. Second, we used free energy computational calculations for the reliable prediction of relative free energies between the wild type and mutant enzymes. The ΔΔG values for Y50C and T453I mutant enzymes in complex with FADH2-NADP-ETH were 3.34 (+/−0.55) and 8.11 (+/−0.51) kcal/mol, respectively, compared to the wild type complex. The positive ΔΔG values indicate that the wild type complex is more stable than the mutants, with the T453I complex being the least stable. These are the first results shedding light on the molecular basis of ETH resistance, namely reduced complex stability of mutant EthA.

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How Aromatic Are Molecular Nanorings? The Case of a Six-Porphyrin Nanoring

10.26434/chemrxiv.14035919 ◽

2021 ◽

Author(s):

irene casademont-reig ◽

Raúl Guerrero-Avilés ◽

Eloy Ramos-Cordoba ◽

Miquel Torrent-Sucarrat ◽

Eduard Matito

Keyword(s):

Low Temperatures ◽

Ring Current ◽

Computational Method ◽

Oxidation States ◽

Aromatic Rings ◽

Persistent Currents ◽

Conjugated Molecules ◽

Strong Magnetic Fields ◽

The Poor ◽

Computational Calculations

<div> <div> <div> <p>Large conjugated rings give rise to novel promising structures that can sustain persistent currents at low temperatures even in the presence of strong magnetic fields. One of the most interesting such molecules was recently synthesized [Anderson et al., Nature, 2017, 541, 3512] in the form of a six-porphyrin nanoring structure, which, according to the authors, in its +6-oxidation state (c-P66+) sustained an aromatic ring current involving 78π electrons; one of the largest aromatic rings ever produced. In this paper, we have provided compelling evidence that this molecule is not aromatic, as it was incorrectly inferred from computational calculations that suffer from large delocalization errors. A thorough analysis of four oxidation states of the six-porphyrin nanoring re- veals that the main reason behind the poor aromaticity of these nanorings is the low delocalization in the transition from the porphyrins to the bridging butadiyne linkers, which disrupts the overall conjugated circuit. These results highlight the importance of choosing an adequate computational method to study large conjugated molecules and the appropriate aromaticity descriptors to identify the part of the molecule that is responsible for the loss of aromaticity. We believe the strategy here employed will be helpful in designing new large aromatic molecular nanorings. </p> </div> </div> </div>

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