0000000000002399

AUTHOR

Rafael Viruela

0000-0002-0694-0517

showing 40 related works from this author

Theoretical study of the molecular structure and the stability of neutral and reduced tetracyanoethylene

2003

Abstract The molecular structure and the stability of neutral, anionic, and dianionic tetracyanoethylene (TCNE) have been studied with MP2, coupled-cluster (CC), and density functional theory (DFT) procedures. The optimized geometries are in agreement with the available experimental data, although significant deviations for the CN bond distance have been obtained at the MP2 level. The adiabatic electron affinity of TCNE calculated with the B3LYP method is overestimated by 0.32 eV. In the light of the CC results, the source of such an overestimation is suggested to lie on the theoretical approach, rather than on a too low experimental value.

Electron densityGeneral Physics and AstronomyTetracyanoethyleneMolecular physicsBond lengthchemistry.chemical_compoundMolecular geometrychemistryComputational chemistryAb initio quantum chemistry methodsElectron affinityPhysics::Atomic and Molecular ClustersMoleculeDensity functional theoryPhysics::Chemical PhysicsPhysical and Theoretical ChemistryChemical Physics Letters
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Relationship between Electron Affinity and Half-Wave Reduction Potential: A Theoretical Study on Cyclic Electron-Acceptor Compounds.

2016

A high-level ab initio protocol to compute accurate electron affinities and half-wave reduction potentials is presented and applied for a series of electron-acceptor compounds with potential interest in organic electronics and redox flow batteries. The comprehensive comparison between the theoretical and experimental electron affinities not only proves the reliability of the theoretical G3(MP2) approach employed but also calls into question certain experimental measurements, which need to be revised. By using the thermodynamic cycle for the one-electron attachment reaction A+e- →A- , theoretical estimates for the first half-wave reduction potential have been computed along the series of ele…

chemistry.chemical_classification010304 chemical physicsChemistryAb initioSolvationElectronElectron acceptor010402 general chemistry01 natural sciencesRedoxAtomic and Molecular Physics and Optics0104 chemical sciencesReduction (complexity)Ab initio quantum chemistry methodsComputational chemistryChemical physicsElectron affinity0103 physical sciencesPhysical and Theoretical ChemistryChemphyschem : a European journal of chemical physics and physical chemistry
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On the electron affinity of TCNQ

2004

The electron affinity of 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) has been studied with density functional theory and coupled cluster (CC) procedures. The adiabatic electron affinity of TCNQ calculated with the B3LYP method is about 1 eV higher than the available experimental value. At the CCSD(T) level, the theoretical result is overestimated by more than 0.4 eV. The electron affinity computed for TCNQ is larger than that obtained for tetracyanoethylene at all levels of calculation, exactly the opposite of what is observed experimentally. Accordingly, a call for an additional empirical measurement of such a property is made.

chemistry.chemical_compoundCoupled clusterElectron affinity (data page)ChemistryGeneral Physics and AstronomyDensity functional theoryPhysical and Theoretical ChemistryAtomic physicsTetracyanoethyleneAdiabatic processChemical Physics Letters
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Theoretical description of the Raman spectrum of a vinylene-bridged quaterthiophene oligomer

2003

The Raman spectrum of a quaterthiophene oligomer incorporating a central vinylene spacer has been investigated using density functional theory B3LYP/6-31G** calculations. The spectrum has been fully assigned with the aid of the calculations and in comparison with unsubstituted quaterthiophene. The spectrum preserves most of the vibrational features of linear oligothiophenes. The vibrations of the vinylene spacer are clearly differentiated from those of the rest of the chain. The vinylene spacer increases the conjugation length of the molecule and induces a frequency downshift of < 20 cm 21 for the normal modes associated with the nas(CyC) and ns(CyC) vibrations of the thiophene rings. The m…

Organic ChemistryOligomerAnalytical ChemistryInorganic Chemistrychemistry.chemical_compoundsymbols.namesakeCrystallographychemistryComputational chemistryNormal modesymbolsThiopheneMoleculeDensity functional theoryRaman spectroscopySpectroscopyJournal of Molecular Structure
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Acene-type donors bearing one 1,3-dithiole ring

1999

Abstract A series of acene-type donors bearing only one 1,3-dithiole ring have been synthesized by following a Wittig-Horner reaction from 7 H -benz[ d,e ]anthracen-7-one and several phosphonate esters. The excellent donor properties have been studied using both experimental techniques and quantum-chemical calculations and reveal that the extraction of the first electron in the oxidation process occurs from the dithiole ring (0.42 e) and the acene unit (0.58 e).

Bearing (mechanical)StereochemistryChemistryMechanical EngineeringMetals and AlloysElectron donorCondensed Matter PhysicsRing (chemistry)Chemical synthesisPhosphonateMedicinal chemistryElectronic Optical and Magnetic Materialslaw.inventionchemistry.chemical_compoundMechanics of MaterialslawMaterials ChemistryMoleculeAceneUnit (ring theory)Synthetic Metals
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A new series of π-extended tetrathiafulvalene derivatives incorporating fused furanodithiino and thienodithiino units: a joint experimental and theor…

2004

A new family of tetrathiafulvalenes has been prepared. The materials exhibit complex redox behaviour related to the electronic influence of the 1,4-dithiin moieties embedded within the framework of the molecules. The X-ray crystal structure of compound 4 reveals an unusual non-planar conformation of the heterocyclic compound, with the TTF fragment adopting a boat conformation. Theoretical calculations, performed at the DFT level (B3P86/6-31G*), confirm the boatlike structure (C2v symmetry) as the most stable conformation for this family of tetrathiafulvalenes. Upon oxidation, electrons are extracted from the whole molecule and the radical cations and dications remain highly distorted from p…

Valence (chemistry)ChemistryStereochemistryCyclohexane conformationSupramolecular chemistryAromaticityGeneral ChemistryCrystal structurePlanarity testingCrystallographychemistry.chemical_compoundMaterials ChemistryMoleculeTetrathiafulvaleneJ. Mater. Chem.
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π conjugation across the tetrathiafulvalene core: Synthesis of extended tetrathiafulvalene derivatives and theoretical analysis of their unusual elec…

2000

A series of extended tetrathiafulvalene (TTF) derivatives bearing one or two 1,4-dithiafulven-6-yl substitutents has been prepared. The new compounds present remarkable electrochemical singularities compared with other TTF derivatives, which are strongly affected by the nature of the substitution on the lateral heterocycle(s). This unusual electrochemical behaviour follows a square-scheme sequence and is attributed to structural changes upon oxidation of the pi-donating molecules. Digital simulations of the electrochemical data have been used to reach the values of the kinetic and thermodynamic constants involved in the square scheme. Theoretical calculations establish an important contribu…

Pi systemOrganic ChemistryInorganic chemistryNonlinear opticsGeneral ChemistryConjugated systemElectrochemistryCatalysischemistry.chemical_compoundCrystallographychemistryAb initio quantum chemistry methodsMoleculeCyclic voltammetryTetrathiafulvalene
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Controlled Self-Assembly of Electron Donor Nanotubes

2009

We employ a combination of urea-urea hydrogen bonds and pi-pi stacking interactions to obtain soluble self-assembled nanotubes decorated with electron-donor TTF derivatives on the periphery. We have investigated the structure and stability of the nanotubes with a combination of experiments and high-level DFT calculations. We also demonstrate that the association process can be controlled by changes in the hydrogen-bonding ability of the solvent and electrochemically.

Solventchemistry.chemical_compoundchemistryTtf derivativesChemical engineeringHydrogen bondOrganic ChemistryStackingNanotechnologyElectron donorSelf-assemblyPhysical and Theoretical ChemistryBiochemistryOrganic Letters
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Concave Tetrathiafulvalene-Type Donors as Supramolecular Partners for Fullerenes

2007

The cap fits! A new class of concave π-extended tetrathiafulvalene (TTF) derivatives, truxene-TTFs, were prepared and characterized, and their self-assembly with fullerenes was investigated (see picture). Truxene-TTFs represent the first example of TTF-related electron donors that serve, without chemical modification, as monotopic receptors for fullerenes in solution. (Chemical Equation Presented). © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.

chemistry.chemical_compoundCrystallographyFullerenechemistryStereochemistrySupramolecular chemistryChemical modificationGeneral ChemistrySelf-assemblyGeneral MedicineChemical equationCatalysisTetrathiafulvaleneAngewandte Chemie
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Weighting non-covalent forces in the molecular recognition of C60. Relevance of concave–convex complementarity

2008

The relative contributions of several weak intermolecular forces to the overall stability of the complexes formed between structurally related receptors and [60]fullerene are compared, revealing a discernible contribution from concave–convex complementarity. Viruela Martin, Pedro Manuel, Pedro.M.Viruela@uv.es ; Viruela Martin, Rafael, Rafael.Viruela@uv.es ; Orti Guillen, Enrique, Enrique.Orti@uv.es

FULLERENESUNESCO::QUÍMICANon covalentBUILDING-BLOCK12-TETRACYANO-9:QUÍMICA [UNESCO]CatalysisMolecular recognitionCHEMISTRYSYSTEMSMaterials ChemistryUNESCO::QUÍMICA::Química orgánicaCARBON NANORINGSChemistryCARBON NANORINGS; BUILDING-BLOCK; FULLERENES; 11111212-TETRACYANO-910-ANTHRAQUINODIMETHANE; COMPLEXATION; DERIVATIVES; RECEPTORS; CHEMISTRY; SYSTEMSCOMPLEXATIONDERIVATIVESIntermolecular force:QUÍMICA::Química orgánica [UNESCO]Metals and AlloysRegular polygonMolecular recognition ; Concave-convex ; Stability ; C60 ; Intermolecular forcesGeneral ChemistrySettore CHIM/06 - Chimica Organica11Intermolecular forcesSurfaces Coatings and FilmsElectronic Optical and Magnetic MaterialsWeighting12Concave-convexbody regionsRECEPTORSC60CrystallographyChemical physicsComplementarity (molecular biology)10-ANTHRAQUINODIMETHANECeramics and CompositesMolecular recognitionStability
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Experimental and theoretical studies into the structural perturbations between neutral, oxidised and reduced forms of 1,4-dithiinoquinoxaline derivat…

2000

The syntheses and electrochemistry of thieno[3',4'r5,6][1,4]dithiino[2,3-b]quinoxaline (9), 2,3-bis(methylsulfanyl)[1,4]dithiino[2,3-b]quinoxaline (16) and 2,3-ethylenedisulfanyl[1,4]dithiino[2,3-b]quinoxaline (17) are reported, together with the X-ray crystal structures of 9, 16 and the charge-transfer complex 9.TCNQ. In the thieno derivative 9, the molecular structure undergoes a significant change from a boat conformer to a planar system, upon oxidation with TCNQ. Theoretical calculations show that oxidation leads to planarisation of the molecular structure due to the aromatisation of the dithiine moiety. The study of the oxidised/reduced species helps to rationalise the electrochemical …

NitrileChemistryStereochemistryGeneral ChemistryCrystal structureCharge-transfer complexElectrochemistrychemistry.chemical_compoundCrystallographyQuinoxalineMaterials ChemistryMoietyMoleculeConformational isomerismJournal of Materials Chemistry
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Donor-π-Acceptor Species Derived from Functionalised 1,3-Dithiol-2-ylidene Anthracene Donor Units Exhibiting Photoinduced Electron Transfer Propertie…

1998

Steric interactions between the anthraquinoid core and the 1,3-dithiole and dicyanomethylene groups play a key role in determining the physical properties of system 1. The intramolecular charge transfer properties of this donor–π-acceptor species have been explored and cyclic voltammetric data, X-ray crystal structures and ab initio calculations are also reported.

Steric effectsOrganic ChemistryDithiolGeneral ChemistryCrystal structurePhotochemistryAcceptorCatalysisPhotoinduced electron transferchemistry.chemical_compoundCrystallographyElectron transferchemistryAb initio quantum chemistry methodsIntramolecular forceChemistry - A European Journal
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The Role of Planarity versus Nonplanarity in the Electronic Communication of TCAQ-Based Push–Pull Chromophores

2018

Donor-acceptor-substituted alkynes, endowed with 11,11,12,12-tetracyano-9,10-anthraquinodimethane (TCAQ) and N,N-dimethylaniline (DMA) units, have been further functionalized by a [2+2] cycloaddition with tetracyanoethylene (TCNE) followed by a subsequent retro-electrocyclization to form distorted nonplanar structures with bridging 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) units. Comprehensive spectroscopic, electrochemical, and computational studies have been carried out to compare the electronic communication in planar (alkyne bridges) and nonplanar (TCBD bridges) TCAQ-based push-pull chromophores. Cyclic voltammetry and UV/Vis absorption measurements confirm the electronic communication be…

chemistry.chemical_classificationMaterials science010405 organic chemistryAlkyneGeneral ChemistryTetracyanoethyleneChromophore010402 general chemistry01 natural sciencesPlanarity testingCycloaddition3. Good health0104 chemical scienceschemistry.chemical_compoundCrystallographychemistryElectronic communicationDensity functional theoryCyclic voltammetry
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Bowl-shape electron donors with absorptions in the visible range of the solar spectrum and their supramolecular assemblies with C 60

2012

We describe the synthesis, electronic, optical and photophysical properties of a family of three electron-donor bowl-shaped organic molecules that absorb light in the whole range of the visible spectrum (up to 800 nm in one case), and associate C60 in solution with binding constants in the range of 104–102 M−1 as measured from both UV-vis and fluorescence titrations in several solvents. These molecules are π-extended derivatives of tetrathiafulvalene, based on a truxene core to which two or three units of dithiole are covalently attached. The inclusion of the bulky dithiole groups is responsible for their bowl-shape geometry, which allows them to associate with C60, and their electron-donor…

010405 organic chemistrySupramolecular chemistryGeneral Chemistry010402 general chemistryPhotochemistry01 natural sciences0104 chemical sciencesPhotoexcitationchemistry.chemical_compoundchemistryIntramolecular forceUltrafast laser spectroscopyDensity functional theoryAbsorption (chemistry)TetrathiafulvaleneVisible spectrum
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Electronic spectra of tetrathiafulvalene and its radical cation: analysis of the performance of the time-dependent DFT approach

2002

Abstract The electronic spectra of tetrathiafulvalene and its radical cation have been studied within the framework of the time-dependent density functional theory by using a conventional hybrid functional. The behaviour of the method has been analyzed through the computed vertical excitation energies for the low-lying electronic excited states. Although the procedure provides a correct description of many of the features of the spectra, deviations in the range 0.4–0.7 eV have been obtained for several transitions, from which one can conclude misleading assignments.

Range (particle radiation)General Physics and AstronomyMolecular physicsSpectral lineHybrid functionalchemistry.chemical_compoundRadical ionchemistryComputational chemistryExcited stateDensity functional theoryPhysical and Theoretical ChemistryTetrathiafulvaleneExcitationChemical Physics Letters
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A theoretical study of neutral and reduced tetracyano-p-quinodimethane (TCNQ)

2004

Abstract The molecular structure of neutral, anionic, and dianionic tetracyano- p -quinodimethane (TCNQ), as well as the electron affinity of TCNQ, have been studied with HF, MP2, and different density functional theory (DFT) procedures. The optimized geometries compare well with the available experimental data, although the C N bond distance is not correctly described at the MP2 level. The calculated parameters are rather insensitive to the basis set employed, and the addition of diffuse functions does not yield significant changes. When the extra electrons are added, the central ring of TCNQ progressively becomes more aromatic. Compared with the CCSD(T) estimate, the value of the adiabati…

chemistry.chemical_classificationElectron acceptorCondensed Matter PhysicsBiochemistryBond lengthMolecular geometrychemistryComputational chemistryYield (chemistry)Electron affinityMoleculePhysical chemistryDensity functional theoryPhysical and Theoretical ChemistryBasis setJournal of Molecular Structure: THEOCHEM
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Valence bands of poly(methylmethacrylate) and photoion emission in vacuum ultraviolet region

1992

Photoion and photoelectron yields were measured for poly(methylmethacrylate) in the photon energy region of 8–40 eV using synchrotron radiation. Further, the valence‐band structure was investigated with ultraviolet photoelectron spectra and valence effective Hamiltonian calculations. A significant difference was observed between the photon energy dependencies of photoion and photoelectron yields. The threshold energy for photoion emission was found to be 10.5 eV, while that for photoelectron emission was 8.5 eV, indicating holes created near the valence‐band top do not contribute to the ion emission. At the higher‐energy region, the ion emission efficiency was found to be enhanced in the ph…

PmmaValence BandsAstrophysics::High Energy Astrophysical PhenomenaGeneral Physics and AstronomySynchrotron radiationPhotoelectron photoion coincidence spectroscopyAstrophysics::Cosmology and Extragalactic AstrophysicsPhoton energymedicine.disease_causeSpectral lineX-ray photoelectron spectroscopyEv Range 10−100:FÍSICA [UNESCO]medicinePmma ; Ion Emission ; Electron Emission ; Photoelectron Spectroscopy ; Ev Range 10−100 ; Valence Bands ; Band StructurePhysics::Atomic and Molecular ClustersIon EmissionPhysics::Atomic PhysicsElectron EmissionBand StructureAstrophysics::Galaxy AstrophysicsValence (chemistry)ChemistryPhotoelectron SpectroscopyUNESCO::FÍSICAThreshold energyAtomic physicsUltraviolet
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Aminopyrimidine-Based Donor–Acceptor Chromophores: Push–Pull versus Aromatic Behaviour

2008

Novel 2-aminopyrimidines substituted with two electron-donor dialkylamino groups and either one dicyanovinyl (4a–d) or one tricyanovinyl (7a–d) electron-acceptor group have been synthesized, and the balance between their push–pull character and their aromatic behaviour has been studied by experimental (spectroscopic, electrochemical and X-ray analysis) and theoretical (DFT/B3LYP/6-31G**) methods. Calculations reveal that the push–pull character is energetically favoured with respect to the preservation of the aromaticity of the pyrimidine ring. X-ray analysis of 7a confirms the theoretical predictions and reveals a strong distortion from planarity due to the steric interaction between the t…

Steric effectsCrystallographyChemistryComputational chemistryIntramolecular forceOrganic ChemistryMoleculeAromaticityPhysical and Theoretical ChemistryChromophoreRing (chemistry)HOMO/LUMOAcceptorEuropean Journal of Organic Chemistry
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Highly Conjugatedp-Quinonoidπ-Extended Tetrathiafulvalene Derivatives: A Class of Highly Distorted Electron Donors

2004

A new class of pi-extended TTF-type electron donors (11 a-c) has been synthesized by Wittig-Horner olefination of bianthrone (9) with 1,3-dithiole phosphonate esters (10 a-c). In cyclic voltammetry experiments, donors 11 a-c reveal a single, electrochemically irreversible oxidation-yielding the corresponding dicationic products-at relatively low oxidation potentials (approximately 0.7-0.8 V). Theoretical calculations, performed at the DFT level (B3 P86/6-31 G*), predict a highly-folded C(2h) structure for 11 a. In the ground state, the molecule adopts a double saddle-like conformation to compensate the steric hindrance. The calculations suggest that the intramolecular charge transfer associ…

Steric effectsChemistryOrganic ChemistryGeneral ChemistryConjugated systemPhotochemistryCatalysisDicationchemistry.chemical_compoundRadical ionIntramolecular forceMoleculeHOMO/LUMOTetrathiafulvaleneChemistry - A European Journal
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A bis(triazole)benzamide receptor for the complexation of halide anions and neutral carboxylic acid guests. Guest-controlled topicity and self-assemb…

2012

Bis(triazole)benzamide 1 has been readily synthesized by means of Cu-catalyzed 1,3-dipolar cycloaddition and its ability to bind halide anions and neutral gallic acid derivative 12GA has been theoretically and experimentally investigated. The cavity defined by the N-H amide group and the vicinal aromatic hydrogens is suitable to form H-bonding arrays with halide guests. The stability of complexes 1·Cl- and 1·Br- is very similar, as DFT calculations predict and 1H NMR titration experiments confirm. The zigzag "anti" conformation of the molecule generates two regions with complementary positive and negative potentials that favor the statistical complexation of two molecules of the neutral car…

AnionsModels Molecularchemistry.chemical_classificationStereochemistryCarboxylic acidOrganic ChemistryCarboxylic AcidsTriazoleTopicityHalideTriazolesBromineBiochemistryCycloadditionchemistry.chemical_compoundchemistryAmideBenzamidesPolymer chemistryMoleculeChlorinePhysical and Theoretical ChemistryDerivative (chemistry)Org. Biomol. Chem.
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Geometric Structure and Torsional Potential of Biisothianaphthene. A Comparative DFT and ab Initio Study

1997

We present a study of the torsional potential of biisothianaphthene and compare it to that of bithiophene. The calculations are performed at the ab initio and semiempirical Hartree−Fock (HF), ab initio post-Hartree−Fock, and density functional theory (DFT) levels. Our study has two major aims:  (i) on the physico-chemical side, to asses the optimal conformation of biisothianaphthene and evaluate the rotational barriers toward coplanar structures and (ii) on the methodological side, to asses the usefulness of DFT approaches. In contrast to previous estimates, the torsional potential of biisothianaphthene is found to differ markedly from that of bithiophene. For biisothianaphthene, strongly r…

ChemistryAb initioStructure (category theory)General ChemistryBiochemistryMolecular physicsCatalysisCrystalColloid and Surface ChemistryComputational chemistryPhysics::Atomic and Molecular ClustersDensity functional theoryTorsional potentialConformational isomerismJournal of the American Chemical Society
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Benzoannulated quinone-type electron acceptors: evolution of the molecular and electronic structures upon reduction

1998

Abstract The molecular and electronic structures of DCNQI and its π-extended derivatives benzo-DCNQI and DCAQI have been investigated using ab initio 6-31G ∗ calculations. The steric hindrance introduced by lateral benzoannulation determines the loss of planarity of the DCNQI moiety for DCAQI. The most stable conformation of DCAQI corresponds to a butterfly-type structure, in which the DCNQI ring adopts a boat conformation and the lateral benzene rings remain planar. This structure lies 2.75 kcal mol −1 below the fully planar conformation. MP2/6-31G ∗ calculations including full geometry optimization confirm the greater stability of the butterfly structure. The geometries of the anions and …

Steric effectschemistry.chemical_classificationChemistryCyclohexane conformationAb initioElectron acceptorCondensed Matter PhysicsRing (chemistry)BiochemistryPlanarity testingCrystallographyAb initio quantum chemistry methodsComputational chemistryMoietyPhysical and Theoretical ChemistryJournal of Molecular Structure: THEOCHEM
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Difficulties of density functional theory in predicting the torsional potential of 2,2?-bithiophene

1998

The internal rotation of 2,2′-bithiophene was investigated within the density functional theory (DFT) approach. Fully optimized DFT torsional potentials are compared with Moller–Plesset (MP2) results which predict a fourfold potential with s-cis- and s-trans-gauche minima. DFT calculations fail in describing the energetics of the internal rotation because they favor planar vs. perpendicular conformers. Gradient-corrected functionals provide torsional potentials where the gauche minima have almost vanished and the s-ciss-trans interconversion barriers are twice as high as the barriers obtained at the MP2 level. The use of local functionals augments the shortcomings of the DFT approach. The g…

Quantitative Biology::BiomoleculesChemistryInternal rotationCondensed Matter PhysicsMolecular physicsAtomic and Molecular Physics and OpticsMaxima and minimasymbols.namesakePlanarFourier transformComputational chemistryPhysics::Atomic and Molecular ClustersPerpendicularsymbolsDensity functional theoryPhysics::Chemical PhysicsPhysical and Theoretical ChemistryTorsional potentialConformational isomerismInternational Journal of Quantum Chemistry
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La movilidad geográfica de búlgaros y rumanos durante la Gran Recesión en España

2021

El objetivo de este artículo es analizar las pautas de movilidad de los inmigrantes procedentes de Bulgaria y Rumania durante la grave crisis económico-laboral que afecta a España. La información utilizada procede de entrevistas en profundidad a migrantes búlgaros y rumanos, que se completa con datos del Instituto Nacional de Estadística y del Ministerio de Empleo y Seguridad Social. Los resultados muestran el fuerte incremento de la movilidad interprovincial de trabajadores, sobre todo en los primeros años y con un destacado protagonismo de los varones, y el progresivo aumento de la migración internacional, que adopta diversas formas: retorno, migración circular entre el lugar de origen y …

Mobilité géographiqueMobilitat geogràficaEspagneEconomic crisisGeographic mobilityGeography Planning and DevelopmentEspañaImmigrés bulgares et roumainsInmigrantes búlgaros y rumanosImmigrants búlgars i romanesosMovilidad geográficaSpainRomanian and bulgarian immigrationEspanyaCrise économiqueEarth-Surface ProcessesCrisis económicaCrisi econòmica
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Synthesis and radical coupling of pyridine-bridged π-extended tetrathiafulvalene (TTF)-type donors and push–pull analogues

2007

A new family of pi-extended TTF analogues (3a-c) and D-pi-A chromophores (5a-c), in which the electroactive units (1,3-dithiole rings and 2,2-dicyanovinyl groups) are connected through a pyridine bridge with a meta substitution pattern, is reported. The redox behavior of these compounds has been investigated by cyclic voltammetry and theoretical calculations performed at the B3P86/6-31G** level. Unlike many pi-extended TTF derivatives, the 1,3-dithiole rings in compounds 3a-c do not behave independently and two oxidation processes are observed with an anodic separation ranging from 50 to 150 mV. Calculations show that electrons are equally extracted from both dithiole rings. A biradical str…

Organic ChemistryChromophoreRing (chemistry)PhotochemistryBiochemistryAcceptorDicationchemistry.chemical_compoundCrystallographyRadical ionchemistryPyridineMoietyPhysical and Theoretical ChemistryTetrathiafulvaleneOrg. Biomol. Chem.
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Raman and theoretical study of the solvent effects on the sizable intramolecular charge transfer in the push-pull 5-(dimethylamino)-5'-nitro-2,2'-bit…

2006

In this paper, we analyze the degree of intramolecular charge transfer in a push-pull π-conjugated system, 5-(dimethylamino)-5'-nitro-2,2'-bithiophene, from changes in frequencies and relative intensities of its strongestRaman scatterings in a bunch of solvents with different polarities. Density functional theory (DFT) was used as a support of the experimental study. Solvent effects on the molecular and electronic structures and on the vibrational properties were estimated by performing B3LYP/6-31G** calculations within the framework of the polarized continuum model (PCM) developed by Tomasi. Calculations reveal that the molecule is highly polarized in the ground state and behaves as a very…

ChemistryPhotochemistryMolecular physicsSolventsymbols.namesakeIntramolecular forcesymbolsMoleculeDensity functional theoryPhysics::Chemical PhysicsPhysical and Theoretical ChemistrySolvent effectsRaman spectroscopyGround stateRaman scatteringThe journal of physical chemistry. A
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A Fully Conjugated TTF-π-TCAQ System: Synthesis, Structure, and Electronic Properties

2011

The synthesis of the first fully conjugated tetrathiafulvalene-tetracyano-p-quinodimethane ((TTF)-TCNQ)-type system has been carried out by means of a Julia-Kocienski olefination reaction. In particular, a tetracyanoanthraquinodimethane (TCAQ) formyl derivative and two new sulfonylmethyl-exTTFs (exTTF = 2-[9-(1,3-dithiol-2-ylidene)anthracen-10(9H)-ylidene]-1,3-dithiole)--prepared as new building blocks--were linked. A variety of experimental conditions reveal that the use of sodium hexamethyldisilazane (NaHMDS) as base in THF afforded the E olefins with excellent stereoselectivity. Theoretical calculations at the B3LYP/6-31G** level point to highly distorted exTTF and TCAQ that form an almo…

010405 organic chemistryChemistryOrganic ChemistryGeneral ChemistryConjugated system010402 general chemistryPhotochemistry01 natural sciencesAcceptorCatalysis0104 chemical sciencesIonchemistry.chemical_compoundRadical ionExcited stateGround stateDerivative (chemistry)TetrathiafulvaleneChemistry - A European Journal
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A Study by Spectroelectrochemical FTIR and Density Functional Theory Calculations of the Reversible Complexing Ability of an Electroactive Tetrathiaf…

2006

We report on the study of the electrochemically targeted complexation/expulsion of a metal cation (Ba2+) by a crown ether tetra(thiomethyl)tetrathiafulvalene derivative (crown-TTM-TTF). Real time, in situ FTIR spectroelectrochemistry was used to obtain spectroscopic evidence of this electrochemically triggered phenomenon. Density functional theory calculations allowed the spectral information collected to be assigned. Both experimental and theoretical results clearly show that neutral crown-TTM-TTF complexes well Ba2+. Complexation is evidenced by a significant downshift of the frequency corresponding to the asymmetric stretching of the C-O-C ether groups. Concerning the cation crown-TTM-TT…

chemistry.chemical_classificationInorganic chemistryEther02 engineering and technology010402 general chemistry021001 nanoscience & nanotechnologyElectrochemistry01 natural sciences0104 chemical sciencesDicationchemistry.chemical_compoundchemistryPhysical chemistryDensity functional theoryPhysical and Theoretical ChemistryFourier transform infrared spectroscopy0210 nano-technologyDerivative (chemistry)Crown etherTetrathiafulvaleneThe Journal of Physical Chemistry A
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Diskrete supramolekulare Donor-Akzeptor-Komplexe

2009

ChemistryGeneral MedicineAngewandte Chemie
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A bis-exTTF macrocyclic receptor that associates C60 with micromolar affinity

2010

An exTTF-based macrocyclic receptor that associates C(60) with a binding constant10(6) M(-1) in chlorobenzene at room temperature is described. This represents an improvement of 3 orders of magnitude with respect to the previous examples of exTTF-based receptors and one of the highest binding constants toward C(60) reported to date.

chemistry.chemical_compoundColloid and Surface ChemistryStereochemistryChemistryChlorobenzeneGeneral ChemistryReceptorBiochemistryBinding constantCatalysisOrders of magnitude (mass)
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Synthesis, properties and charge transfer complexes of covalently attached [60]fullerene-tetrathiafulvalenes

1997

Abstract The synthesis of several fulleropyrrolidines bearing differently substitued tetrathiafulvalenes is reported. The synthetic approach used allows the introduction of ethylene spacers between the TTF and the C 60 core. Charge transfer complexes obtained from these [60]fullerene-TTF systems by reaction with tetrafluoro-tetracyano-p-quinodimethane (TCNQF 4 ) show a semiconducting behaviour; theoretical calculations predict an intramolecular CT band from the TTF moiety to the C 60 core.

Materials scienceEthyleneFullereneStereochemistryCharge (physics)General ChemistryCondensed Matter PhysicsCrystallographychemistry.chemical_compoundchemistryCovalent bondIntramolecular forceMoietyGeneral Materials Science
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Effects of Carbon-sp3 Bridging on the Electronic Properties of Oligothiophenes

1999

Abstract The electronic properties of rigidified, carbon sp 3 -bridged bithiophenes and terthiophenes have been investigated using density functional theory calculations, sp 3 Bridging has no effect on the bandgap other than that associated to the planarization of the system. Rigidification significantly improves the ability of oligothiophenes as electron donors but diminishes their electron accepting capacity. Grafting of substituents at the sp 3 bridging carbon slightly modifies the electronic properties.

Bridging (networking)Materials scienceBand gapMechanical EngineeringMetals and AlloysElectronic structureElectronCondensed Matter PhysicsPhotochemistryElectronic Optical and Magnetic MaterialsMechanics of MaterialsComputational chemistryChemical-mechanical planarizationMaterials ChemistryDensity functional theoryElectronic propertiesSynthetic Metals
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Donor-π-acceptors containing the 10-(1,3-dithiol-2-ylidene)anthracene unit for dye-sensitized solar cells

2012

Two donor-acceptor molecular tweezers incorporating the 10-(1,3-dithiol-2-ylidene)anthracene unit as donor group and two cyanoacrylic units as accepting/anchoring groups are reported as metal-free sensitizers for dye-sensitized solar cells. By changing the phenyl spacer with 3,4-ethylenedioxythiophene (EDOT) units, the absorption spectrum of the sensitizer is red-shifted with a corresponding increase in the molar absorptivity. Density functional calculations confirmed the intramolecular charge-transfer nature of the lowest-energy absorption bands. The new dyes are highly distorted from planarity and are bound to the TiO(2) surface through the two anchoring groups in a unidentate binding for…

optical propertiesAbsorption spectroscopypigments010402 general chemistryPhotochemistrydyes01 natural sciences7. Clean energyCatalysischemistry.chemical_compound[CHIM]Chemical SciencesComputingMilieux_MISCELLANEOUSAnthracene010405 organic chemistryOrganic ChemistryDithiolGeneral ChemistryMolar absorptivity0104 chemical sciencesDye-sensitized solar cellchemistryIntramolecular forcesensitizerssolar cellsAbsorption (chemistry)absorptionMolecular tweezers
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Flexibility of TTF. a theoretical study

1999

Abstract The folding of tetrathiafulvalene along the S···S axes has been investigated using highly-accurate quantum-chemical calculations. A very flat, two-fold potential is found for neutral TTF where minima correspond to boat conformations (θ ≈ 15–20 °). The flatness of the folding potential indicates that TTF is conformationally more flexible than usually thought.

Flexibility (anatomy)ChemistryMechanical EngineeringFlatness (systems theory)Metals and AlloysCondensed Matter PhysicsElectronic Optical and Magnetic MaterialsFolding (chemistry)Maxima and minimachemistry.chemical_compoundmedicine.anatomical_structureMechanics of MaterialsChemical physicsAb initio quantum chemistry methodsComputational chemistryMaterials ChemistrymedicineMoleculeTetrathiafulvaleneSynthetic Metals
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A new type of pi-electron donors with one dithiole unit: Substituted 7-(1,3-dithiol-2-ylidene)-7-hydrobenz[d,e]anthracenes

1999

New electron donors 11a–c bearing only one 1,3-dithiole ring conjugated with an acene backbone have been synthesized by Wittig–Horner reactions from 7H-benz[d,e]anthracen-7-one (10) and differently substituted phosphonate esters 9a–c. The donor properties of 11 have been characterized by means of both experimental techniques and quantum chemical calculations. Cyclic voltammetry measurements on the novel compounds predict donor abilities comparable to those of TTF and BEDT-TTF. The voltammograms show a multi-stage redox behaviour with oxidation up to the trication, where the first two oxidation processes take place at very close potentials. These processes have been assigned to a simultaneou…

chemistry.chemical_compoundChemistryIntramolecular forceOrganic ChemistryDithiolAromaticityPhysical and Theoretical ChemistryConjugated systemRing (chemistry)PhotochemistryAceneRedoxDication
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The First sulfur-containing twin-DCNQI-type acceptor

1994

chemistry.chemical_classificationMechanics of MaterialsChemistryMechanical EngineeringPolymer chemistryOrganic chemistryGeneral Materials ScienceElectronic structureElectron acceptorSulfur containingAcceptorChemical synthesisAdvanced Materials
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Electronic Interactions in a New π-Extended Tetrathiafulvalene Dimer

2006

The first pi-extended tetrathiafulvalene (exTTF) dimer in which the two exTTF units are covalently connected by 1,3-dithiole rings has been obtained in a multistep synthetic procedure involving the Ullmann cross-coupling reaction by using copper(I) thiophene-2-carboxylate (CuTC). The electronic spectrum reveals a significant electronic interaction between the exTTF units. The electrochemical study carried out by cyclic voltammetry in solution and in thin-layer conditions, and the electrochemical simulation and spectroelectrochemical (SEC) measurements confirm the electronic communication and show that the oxidation of dimer 14 occurs as two consecutive 2 e(-) processes D(0)-D(0)-->D(2+)-D(0…

AnthracenesAnthraceneDimerOrganic Chemistrychemistry.chemical_elementStereoisomerism[CHIM.MATE]Chemical Sciences/Material chemistryGeneral ChemistryPhotochemistryElectrochemistryCopperCatalysisDelocalized electronchemistry.chemical_compoundCrystallographyModels ChemicalchemistryHeterocyclic CompoundsCovalent bondElectrochemistryElectronicsCyclic voltammetryDimerizationOxidation-ReductionTetrathiafulvaleneChemistry - A European Journal
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The Interplay of Inverted Redox Potentials and Aromaticity in the Oxidized States of New π-Electron Donors: 9-(1,3-Dithiol-2-ylidene)fluorene and 9-(…

2006

Derivatives of 9-(1,3-dithiol-2-ylidene)fluorene (9) and 9-(1,3-dithiol-2-ylidene)thioxanthene (10) have been synthesised using Horner-Wadsworth-Emmons reactions of (1,3-dithiol-2-yl)phosphonate reagents with fluorenone and thioxanthen-9-one. X-ray crystallography, solution electrochemistry, optical spectroscopy, spectroelectrochemistry and simultaneous electrochemistry and electron paramagnetic resonance (SEEPR), combined with theoretical calculations performed at the B3P86/6-31G** level, elucidate the interplay of the electronic and structural properties in these molecules. These compounds are strong two-electron donors, and the oxidation potentials depend on the electronic structure of t…

Organic ChemistryThioxantheneDithiolAromaticitySulfoxideGeneral ChemistryFluorenePhotochemistryCatalysisDicationchemistry.chemical_compoundchemistryFluorenoneRadical ionChemistry - A European Journal
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First signals of electrochemically oxidized species of TTF and TMT-TTF : a study by in situ spectroelectrochemical FTIR and DFT calculations

2003

A first study by in situ FTIR spectroelectrochemistry of TTF and TTM-TTF has been undertaken. The oxidation, in this case, is caused only by electrochemistry, which constitutes a clear advantage over chemical oxidation since no side products are present in the solution. In this context, we obtained the signals of neutral, radical cation, and dication species of TTF and TTM-TTF. The experimental conditions were chosen in order to avoid the possible formation of π-dimer species and to obtain a satisfactory signal-to-noise ratio. A weak signal was detected for TTF and a stronger one for TTM-TTF. The changes induced by the oxidation process in the IR spectra of TTF and TTM-TTF have been analyze…

Analytical chemistryGeneral Physics and AstronomyInfrared spectroscopyContext (language use)02 engineering and technology010402 general chemistry021001 nanoscience & nanotechnologyElectrochemistry01 natural sciencesFourier transform spectroscopy0104 chemical sciencesDicationchemistry.chemical_compoundRadical ionchemistryPhysical chemistryDensity functional theoryPhysical and Theoretical Chemistry0210 nano-technologyTetrathiafulvalene
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Discrete supramolecular donor-acceptor complexes

2009

The renewed interest in noncovalently associating electroactive molecules arises in part from the quest for new organic materials that convert solar energy into electrical/ chemical equivalents. In this context, the formation of charge-separated states is a key prerequisite. Charge-transfer events triggered by light have been studied in supramolecular donor–acceptor systems based on hydrogen bonds and coordinative metal bonds. Although many of the most widely utilized electroactive fragments feature large pconjugated surfaces, to date the use of p–p aromatic interactions has mainly been limited to the construction of semi-infinite ensembles of chromophores either to achieve charge transport…

chemistry.chemical_compoundChemistryHydrogen bondComputational chemistryTweezersSupramolecular chemistryMoleculePi interactionContext (language use)General ChemistryChromophoreCatalysisTetrathiafulvalene
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