Covalent Bond
Mostrando 1-12 de 190 artigos, teses e dissertações.
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1. Identifying conceptions of the covalent bond: an analysis from a systematic review
The covalent bond is a classical topic in science education because it is fundamental to a considerable number of other concepts and by its ability to interpret several chemical phenomena. However, the process of learning this concept presents some difficulties discussed here. This article brings together the conceptions related to the covalent bond, identif
Química Nova. Publicado em: 2022
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2. GRAPHEN-PHENYL-NH2 AS NANOCARRIER: A DENSITY FUNCTIONAL THEORY STUDY
Recently, graphene and modified graphene as one of the most suitable and the most important carbon nanomaterials have been introduced for drug delivery. In this paper, we have studied the binding characteristics of the EDC-NHS cross-linking process of graphene-phenyl-NH2 and 5-aminolevulinic acid (ALA) drug in both gas and solvent phases by density functiona
Química Nova. Publicado em: 2022
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3. Through-Bond and Through-Space Interactions in [2,2]Cyclophanes
The interpretation of the distortions of the electron distribution in [2,2]cyclophanes (22-CPs) is controversial. Some studies indicate that there is an accumulation of electron density (ρ) outside the cavity of 22-CPs. The nature of through-space (ts) interaction is still under debate. The relative importance of ts and through-bond (tb) is an open question
J. Braz. Chem. Soc.. Publicado em: 2021-07
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4. DFT Study of the Interaction between the Ni2+ and Zn2+ Metal Cations and the 1,2-Dithiolene Ligands: Electronic, Geometric and Energetic Analysis
Density functional theory (DFT) (B3LYP/6-311++G(d,p)) calculations of the interacting strength 1,2-dithiolene anionic ligands with the [M(OH2)4]2+ and [M(OH2)2]2+ complexes (M = Ni and Zn) were performed. Three series of ligands were studied: compounds with an aromatic ring, with an ethylene moiety and with a heterocyclic ring. The ligands have substituents
J. Braz. Chem. Soc.. Publicado em: 23/05/2019
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5. Facial Selectivity between Carbohydrates and Aromatic Amino Acids Explained by a Combination of NCI, NBO and EDA Techniques with NMR Spectroscopy
The influence of electrostatic and dispersion components of intermolecular interactions on the recognition of carbohydrates by aromatic protein residues is important for many biological processes. Interactions between glucose and galactose and aromatic moieties of tryptophan, phenylalanine and histidine were investigated through 1H nuclear magnetic resonance
J. Braz. Chem. Soc.. Publicado em: 08/04/2019
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6. SYNTHESIS, ELECTRONIC AND SPECTRAL PROPERTIES OF NEW 1,3,4-THIADIAZOLE COMPOUNDS AND THE SPECTRAL ANALYSIS OF THEIR CONFORMERS USING DENSITY FUNCTIONAL THEORY
In this study, new 1,3,4-thiadiazole compounds were synthesised and characterised by FT-IR, 1H-NMR, UV-vis spectroscopy and elemental analysis, Furthermore, the relationship between the electronic and spectral data of the 16 conformers of each compound was investigated by theoretical calculations; the theoretical data were compared with the experimental resu
Quím. Nova. Publicado em: 2019-02
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7. DFT STUDY ON THE MECHANISTIC, ENERGETIC AND STRUCTURAL ASPECTS OF ADSORPTION OF TIRAPAZAMINE ONTO PRISTINE AND FUNCTIONALIZED CARBON NANOTUBES
Using density functional theory, noncovalent interactions and two mechanisms of covalent functionalization of drug tirapazamine with pristine, COOH and COCl functionalized carbon nanotube (NT, NTCOOH and NTCOCl) have been investigated. Quantum molecular descriptors of noncovalent configurations were studied. It was specified that binding of drug tirapazamine
Quím. Nova. Publicado em: 2018-01
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8. EPR and Optical Absorption Studies of Cu2+ in Boro-Arsenate Glasses
Electron paramagnetic resonance (EPR) and optical absorption studies of xMgO- (25-x) Li2O-50B2O3-25As2O3 glasses were made by introducing Cu2+ as a spin probe. The EPR spectra of all the glass samples recorded at X-band frequencies have similar spectral features. The Cu2+ ions are in well-defined axial sites, but subjected to small distortion leading to the
Mat. Res.. Publicado em: 01/12/2016
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9. O PARADIGMA DA ESTRUTURA DO DOADOR DE PRÓTON NA FORMAÇÃO DE LIGAÇÕES DE HIDROGÊNIO: COMPLEXO C2H2···6(HF)
The DFT, QTAIM, NBO and ChelpG methods were used in a theoretical study of structural parameters, vibration stretch modes and absorption intensities, electronic properties, molecular orbital analyses and molecular topography of the heptamer C2H2···6(HF) complex. One of the great aims concerns to the studying of the proton donor structure, which is conside
Quím. Nova. Publicado em: 2016-11
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10. Synthesis and Characterization of 1-Methyl-3-Methoxysilyl Propyl Imidazolium Chloride – Mesoporous Silica Composite as Adsorbent for Dehydration in Industrial Processes
Ionic liquid – mesoporous silica composite was synthesized as a new adsorbent for dehydration in industrial processes. An ionic liquid (IL) with proved dehydration properties has been covalently anchored to mesoporous silica. The parameters of the synthesis were studied to produce a solid and stable composite. The material was then characterized by SEM, BE
Mat. Res.. Publicado em: 08/04/2016
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11. A FORMAÇÃO DE LIGAÇÕES DE HIDROGÊNIO π‧‧‧H, F‧‧‧H E C‧‧‧H NOS COMPLEXOS C2H2‧‧‧(HF), C2H2‧‧‧2(HF) E C2H2‧‧‧3(HF)
In this work, a theoretical study on the basis of structural, vibrational, electronic and topological parameters of the C2H2‧‧‧(HF), C2H2‧‧‧2(HF) and C2H2‧‧‧3(HF) complexes concerning the formation of π‧‧‧H, F‧‧‧H and C‧‧‧H hydrogen bonds is presented. The main difference among these complexes is not properly the interact
Quím. Nova. Publicado em: 2016-04
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12. Surface Modification and Spectroscopic Characterization of TiO2 Nanoparticles with 2-Aminoethyl Dihydrogen Phosphate
A common strategy for the surface modification of nano TiO2 and other metal oxide nanoparticles is based on anchor groups using chelating ligands that can carry additional functionalities. This would allow the exploration of further applications of these materials. In the present work, we report the modification of TiO2 nanoparticles
J. Braz. Chem. Soc.. Publicado em: 2015-08