Search results for " density functional calculations"

showing 9 items of 9 documents

DFT computational study on Fe(III)-N,N′-ethylene-bis(salicylideneiminato) derivatives

2005

DFT calculations, at unrestricted B3LYP level, have been performed on the structures of three iron(III) complexes, Fe(Salen)Cl, [Fe(Salen)]+ and [Fe(Salen)OH2]+, where Salen is the anion of Schiff base ligand N,N′-ethylene-bis (salicylideneimine), considering the spin multiplicity (S) values 2, 4 and 6. The results obtained have been compared with the available structural an magnetic experimental data, allowing us to conclude that a stable form of the FeIII(Salen) complex in aqueous solution should be characterized by an energy stabilization of the S=4 compared to the S=6 state.

Aqueous solutionSchiff baseLigandInorganic chemistryCondensed Matter PhysicsBiochemistryIonEthylene bisCrystallographychemistry.chemical_compoundchemistryMetal salen complexesPhysical and Theoretical ChemistryIron Schiff bases Salen Density functional calculationsSettore CHIM/02 - Chimica Fisica
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PREDICTION OF MOESSBAUER PARAMETERS IN A DOUGLAS–KROLL–HESS FRAMEWORK

2008

Douglas-Kroll-Hess density functional calculations Mössbauer spectroscopy
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Conformational Analysis of beta-Lactam-Containing Ferrocene Peptides

2009

The homochiral 3-amino-1-(4-methoxyphenyl)-4-phenyl-beta-lactam (≡ Alm) was conjugated with Boc-Ala giving Ala-Alm (9) after Boc-deprotection (Boc = tert-butoxycarbonyl, Ala = alanine). Coupling of FcCOOH (1) and Boc-Fca (10) with “ dipeptide” 9 resulted in the formation of FcCO-Ala-Alm (12) and the trisamide Boc-Fca-Ala-Alm (13), respectively (Fc = ferrocenyl, Fca = 1’ -aminoferrocene-1-carboxylic acid). The reactions were accomplished by the HOBt/EDC procedure and the products were obtained in good yields (HOBt = 1-hydroxybenzotriazole, EDC = N-(3-dimethylaminopropyl)-N’ -ethylcarbodiimide hydrochloride). Symmetrically 1, 1’ -disubstituted “ tetrapeptide” Fn(CO-Ala-Alm)2 (14) was prepared…

Inorganic Chemistryconformation analysis ; density functional calculations ; hydrogen bonds ; metallocenes ; molecular modelingchemistry.chemical_compoundDipeptidechemistryMolecular modelTetrapeptideFerroceneHydrogen bondStereochemistryIntramolecular forceLactamConjugated system
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Modeling the Interaction of Carbon Monoxide with Flexible Graphene: From Coupled Cluster Calculations to Molecular-Dynamics Simulations

2018

The interaction of CO with graphene was studied at different theoretical levels. Quantum-mechanical calculations on finite graphene models with the use of coronene for coupled cluster calculations and circumcoronene for B97D calculations showed that there was no preferential site for adsorption and that the most important factor was the orientation of CO relative to graphene. The parallel orientation was preferred, with binding energies around 9 kJ mol-1 at the CCSD(T) and B97D levels, which was in good agreement with experimental findings. From a large number of CO-circumcoronene and CO-CO interactions, computed at different distances and randomly generated orientations, parameters were fi…

Materials scienceBinding energy02 engineering and technologyMolecular dynamics010402 general chemistry01 natural scienceslaw.inventionMolecular dynamicschemistry.chemical_compoundAdsorptionlawAtomic and Molecular PhysicsAdsorption; Density functional calculations; Graphene; Interaction energies; Molecular dynamics; Atomic and Molecular Physics and Optics; Physical and Theoretical ChemistryInteraction energiesPhysical and Theoretical ChemistryCanonical ensembleGraphene021001 nanoscience & nanotechnologyAtomic and Molecular Physics and OpticsCoronene0104 chemical sciencesDensity functional calculationsCoupled clusterchemistryChemical physicsIntramolecular forceAdsorptionGrapheneand Optics0210 nano-technologyChemPhysChem
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Zero-field nuclear magnetic resonance spectroscopy of viscous liquids

2014

Abstract We report zero-field NMR measurements of a viscous organic liquid, ethylene glycol. Zero-field spectra were taken showing resolved scalar spin–spin coupling (J-coupling) for ethylene glycol at different temperatures and water contents. Molecular dynamics strongly affects the resonance linewidth, which closely follows viscosity. Quantum chemical calculations have been used to obtain the relative stability and coupling constants of all ethylene glycol conformers. The results show the potential of zero-field NMR as a probe of molecular structure and dynamics in a wide range of environments, including viscous fluids.

Nuclear and High Energy PhysicsZero field NMRzero-field NMRBiophysicsAnalytical chemistryNMR spectroscopy; low field nmr; Density functional calculationsViscous liquidBiochemistrychemistry.chemical_compoundViscosityMolecular dynamicsNMR spectroscopyMoleculePhysics::Chemical Physicsdensity functional theoryCoupling constantlow field nmrtechnology industry and agricultureZero-field NMRNuclear magnetic resonance spectroscopyviscous liquidsCondensed Matter PhysicsScalar couplingDensity functional calculationschemistryChemical physicsDensity functional theoryscalar couplingEthylene glycolViscous liquidsJournal of Magnetic Resonance
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Oxygen-assisted hydroxymatairesinol dehydrogenation: a selective secondary-alcohol oxidation over a gold catalyst.

2013

Selective dehydrogenation of the biomass-derived lignan hydroxymatairesinol (HMR) to oxomatairesinol (oxoMAT) was studied over an Au/Al(2)O(3) catalyst. The reaction was carried out in a semi-batch glass reactor at 343 K under two different gas atmospheres, namely produced through synthetic air or nitrogen. The studied reaction is, in fact, an example of secondary-alcohol oxidation over an Au catalyst. Thus, the investigated reaction mechanism of HMR oxidative dehydrogenation is useful for the fundamental understanding of other secondary-alcohol dehydrogenation over Au surfaces. To investigate the elementary catalytic steps ruling both oxygen-free- and oxygen-assisted dehydrogenation of HMR…

Reaction mechanismMolecular Structure010405 organic chemistryChemistryOrganic ChemistryDiastereomerGeneral Chemistry010402 general chemistryPhotochemistry01 natural sciencesCatalysisLignans0104 chemical sciencesCatalysisOxygenAdsorptionHydroxymatairesinolAlcohol oxidationAlcoholsdehydrogenation density functional calculations gold catalysisReactivity (chemistry)DehydrogenationAdsorptionGoldOxidation-ReductionChemistry (Weinheim an der Bergstrasse, Germany)
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C2-Symmetric Ferrocene-Bis(ureido)peptides : Synthesis, Conformation and Solid-State Structure

2009

The extension of peptide derivatives of ferrocene-1,1'-dicarboxylic acid by formal insertion of NH units between ferrocene and peptide strands results in ferrocene-bis(ureido)-peptides. Experimentally, alanine and dialanine methyl esters were attached to the 1- and 1'-position of 1,1'-diiso-cyanoferrocene to give the corresponding bis(ureido)peptide derivatives 3 and 4. The conformation of 3 has been determined in the solid state by X-ray crystallography. In solution the preferred conformation of 3 and 4 has been elucidated by NMR, IR and CD spectroscopy in concert with DFT calculations. The secondary structure of ferrocene―bis(ureido)peptides 3 and 4 is determined by double bifurcated intr…

chemistry.chemical_classificationAlanineCircular dichroismStereochemistryHydrogen bondPeptideInorganic Chemistrychemistry.chemical_compoundDicarboxylic acidFerrocenechemistryIntramolecular forceconformation analysis; density functional calculations; hydrogen bonds; metallocenes; peptidesProtein secondary structure
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Double-CO32− Centered [CoII5] Wheel and Modeling of Its Magnetic Properties

2010

A high-spin Co(II) cluster with a rare pentagonal molecular structure and formula [Co(5)(CO(3))(2)(bpp)(5)]ClO(4) (1; Hbpp is 2,6-bis(phenyliminomethyl)-4-methylphenolate) has been synthesized and characterized by single-crystal X-ray diffraction. This topology arises from fusing five [Co(2)(bpp)] moieties in a cyclic manner around two CO(3)(2-) central ligands, resulting in propeller-like configuration. The irregular coordination of the carbonate ions to the metal centers results in a combination of coordination numbers (CNs) of the Co(II) ions of five and six. The bulk magnetization of this complicated magnetically exchanged system has been modeled successfully by employing a matrix diago…

crystal structureCoordination numberInorganic chemistrycarbonatesCatalysisIonCoordination complexMetalMagnetizationCluster (physics)Moleculecarbonate ligandschemistry.chemical_classificationOrganic Chemistrycarbonate ligands; carbonates; cobalt; coordination chemistry; density functional calculations; magnetic properties; spin-orbit coupling; crystal structure.General ChemistrySpin–orbit interactioncobaltspin-orbit couplingCrystallographychemistryvisual_artdensity functional calculationscoordination chemistryvisual_art.visual_art_mediummagnetic propertiesChemistry - A European Journal
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Direct detection of 17O NMR in [Gd(DOTA)]- by NMR Spectroscopy

2015

The 17O NMR spectrum of the non-coordinated carboxyl oxygen in the GdIII-DOTA (DOTA = tetraazacyclododecanetetraacetic acid) complex has been observed experimentally. Its line width is essentially unaffected by paramagnetic relaxation due to gadolinium, and is only affected by the quadrupole pathway. The results are supported by the relevant parameters (hyperfine and quadrupole coupling constants) calculated by relativistic DFT methods. This finding opens up new avenues for investigating the structure and reactivity of paramagnetic GdIII complexes used as contrast agents in magnetic resonance imaging.

lanthanide complexesLanthanideGadoliniumchemistry.chemical_elementImaging agentsCatalysisNMR spectroscopy; Density functional calculations; lanthanide complexes; gadolinium; O-17 nmrParamagnetismchemistry.chemical_compoundNMR spectroscopyNuclear magnetic resonanceLanthanidesDOTAHyperfine structureChemistryOrganic ChemistryRelaxation (NMR)General ChemistryNuclear magnetic resonance spectroscopyDensity functional calculationsSettore CHIM/03 - Chimica Generale E InorganicaQuadrupole17O NMR Lanthanides DFTCondensed Matter::Strongly Correlated ElectronsgadoliniumO-17 nmr
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