DFT studies of all fluorothiophenes and their radical cations as candidate monomers for conductive polymers (original) (raw)
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Chemistry Central Journal, 2011
In this paper, electrical and structural properties of mono-, di-, tri-and tetrachlorothiophenes and their radical cations have been studied using the density functional theory and B3LYP method with 6-311++G** basis set. The effects of the number and position of the substituent of chlorine atoms on the properties of the thiophene ring for all chlorothiophenes and their radical cations have been studied. Vibrational frequencies, nuclear chemical shielding constants, spin-density distribution, size and direction of dipole moment vector, ionization potential, electric polarizabilities and NICS values of these compounds have been calculated as well. The analysis of these data showed that double bonds in 3-chlorothiophene are more delocalized and it is the best possible candidate monomer among all chlorothiophenes for the synthesis of corresponding conducting polymers with modified characteristics.
Chemistry of Materials, 2007
Optoelectronic and charge-transport related properties of a series of 3,6-diphenyl-s-tetrazine derivatives, including F, Cl, Br, and CN substituents, have been analyzed. The molecular structure and electronic properties of the new fluorine-containing derivative, bis(3,6-difluorophenyl)-s-tetrazine, were explored by spectroscopic, electrochemical, and theoretical methods. The effects of the substituent on the pristine compound have been assessed from a theoretical perspective, showing that the fluorinated and brominated derivatives have the highest predicted electron mobilities, whereas the cyano derivative is foreseen to undergo the most efficient electron injection process.
Synthetic Metals, 2005
We report the results of a series of ab initio and DFT quantum mechanical calculations on the structure and on the electronic spectral of 2,3-ethylenedioxythiophene-, thiophene-and 2,3-ethylenedithiafurane-containing oligomers. Calculations were performed on oligomers formed by n repeating units, where n ranges from 1 to 8. The bond-length alternation patterns in the -system, the importance of long-range interactions in the stabilization of oligomer chains, the energies of the HOMO and LUMO orbitals and the values of the lowest transition energy have been examined allowing a systematic comparison among the three families of conducting polymers.
Theoretical Treatment of 3-Phenylsubstituted Thiophenes and Their Intrinsically Conducting Polymers
ECS Transactions, 2007
A series of 3-(p-X-phenyl) thiophene monomers (X= -H, -CH3, - OCH3, -COOC2H5, -COCH3,-NO2) was electrochemically polym-erized to furnish polymer films that could be reversibly reduced and oxidized (n- and p-doped). The oxidation potentials of the monomers and formal potentials of the n- and p-doping processes of polymers were correlated with resonance and inductive effects of the substituents on the phenyl ring as well as the semiempirically calculated heats of formation of the monomer radical cations. Moreover, the oxidation potentials of the monomers were correlated with the ionization potentials of the monomers calculated using density functional theory. The reactivity for coupling reactions and the major regioselective products of the polymerization reaction of mono- and oligo-3- phenylthiophenes are inferred from the calculated lone electron spin densities of the respective radical cations. The ionization potentials, which correspond to the energies for generating radical catio...
Macromolecules
The synthesis, electrochemical and spectroscopic properties of a series of thiophene-substituted 1,3-dithiole-2-ones is described. The derivatives Th-3,3, Th-2,2, Th-2,3, Th-3,3(2,2′-Me), and Th3,3-(2,5,2′,5′-Me), have been successfully polymerized by cyclic voltammetry. From the UV−visible spectra of the neutral films, it was determined that PTh-3,3, PTh-2,2 and PTh-2,3 have a bandgap of 2.04, 2.30, and 2.18 eV, respectively. The voltammetric response of Th-3,3(2,2′-Me) was noticeably different from the other polymers. The SNIFTIRS data suggested that Th-3,3(2,2′-Me) was formed by bonding via the β-positions of the thiophene ring, resulting in a poorly conductive polymer. The in situ solid-state modification of PTh-3,3 to produce a new TTF-derivatized polythiophene was carried out. The cyclic voltammetry of the modified polymer confirmed the inclusion of TTF into the backbone of the film.
The Journal of Physical Chemistry C, 2010
Conducting polymers have widespread industrial applications owing to a unique combination of mechanical, optical, and electronic properties. Specifically, the family of poly(alkylenedioxythiophene) derivatives has received much attention due to its inherently high conductivity, environmental stability, and tunability. However, although the electron-donating characteristics of the alkoxy moieties are well-known, the source of the differences among these substitutions has been limited to speculative arguments based on bulk properties. To address these issues, a combined electrochemical and density functional theory (DFT) study was undertaken that reveals the significant electronic and geometric characteristics responsible for the comparative properties of these materials. It was found that the geometry of the alkylenedioxy backbone substitution modulates the π-donating character of the oxygen and that this directly influences the onset of p-doped conductivity. These studies also indicate that this framework equally applies to several other heterocyclic polymer systems. An improved theory for these materials is expected to provide the insight and knowledge base for new conducting polymers with enhanced stability and optoelectronic properties.
Electronic structure of the alkyl, benzyl and methoxy derivatives of polythiophene
Synthetic Metals, 1987
We present a theoretical investigation of the geometric and electronic structures of some derivatives of polythiophene, namely poly-3-methylthiophene, poly-3-ethylthiophene, poly-3-propylthiophene, poly-3-isopropylthiophene, poly-3-benzylthiophene and poly-3-methoxythiophene. The poly-3-alkyland 3-methoxythiophenes have recently attracted a great deal of interest, due to their high conductivities and/or excellent solubility properties. The geometries are optimized with the MNDO semi-empirical method. The MNDO geometries are then used as input for band-structure calculations performed with the VEH (Valence Effective Hamiltonian) technique. We mainly discuss electronic properties such as ionization potentials, bandwidths, band gaps and electron affinities, which are important with regard to the conductivities that could be reached upon doping the polymer.
Theoretical study of perfluorinated oligothiophenes: electronic and structural properties
Polymer, 2004
A quantum-chemical study at the Hartree–Fock, (HF), second order Møeller–Plesset perturbation theory, (MP2), and density functional theory, (DFT), levels was performed on perfluorinated oligothiophenes with the aim to predict the potential utility of these materials in the development of electronic devices based on organic n-type semiconductors. The electronic properties analyzed, such as ionization potential, HOMO–LUMO energy difference and electron affinities suggest that perfluorinated oligothiophenes are more difficult to oxidize, and have a larger band gap in comparison with their non-substituted parent compounds. Structural changes on bond lengths and bond angles between perfluorinated and non-substituted oligothiophenes were also observed. Thus, the incorporation of fluorine atoms into oligomers structure could be an effective way to design materials with n-type conductivity.
Electron spin resonance study of electrochemically generated polythiophene and derivatives
The Journal of Physical Chemistry, 1984
Electrochemically generated poly(3-methylthiophene) and poly(3,4-dimethylthiophene), doped with S03CF< ions, are studied by ESR. It is shown that these compounds exhibit a quasi-metallic behavior. The analysis of the g factor suggests that the electron transport occurs along the carbon skeleton of the polymeric chain for poly(3-methylthiophene); the low-temperature behavior suggests the possibility of a phase transition occurring about 200 K. Organic conducting polymers represent a new class of compounds that have aroused increasing interest, particularly because it is possible to switch them from a semiconducting state (u-10-~ n-' cm-') to a conducting state (u-10-*-103 Q-' cm-') by ~~ ~ ~
Electrochimica Acta, 2002
The electrochemical behavior of a-tetrathiophene (a-TTF) on Pt has been studied from concentrated monomer solutions in acetonitrile or mixtures of acetonitrile/nitrobenzene/DMF with 0.1 M LiClO 4 . For a 1.0 mM a-TTF solution in 50:30:20 acetonitrile/nitrobenzene/DMF, three consecutive oxidation peaks are detected by cyclic voltammetry (CV). In this medium, uniform, insoluble, adherent and black polymeric films are obtained by chronopotentiometry (CP) until 0.5 mA cm − 2 and by chronoamperometry (CA) from 0.900 to 1.200 V versus Ag AgCl, corresponding to the first oxidation stage. Control voltammograms of films synthesized from 1.000 to 1.100 V show a redox pair related to electroactive polarons formed during poly(a-TTF) generation, followed by a reduction peak associated with bipolaronic states. Elemental analysis of polymers allows to determine that their monomeric units always support approximately 0.31 positive charges, balanced with ClO 4 − counterions, and contain a number of ionic couples of Li + ClO 4 − ranging between 0.01 and. 0.06. These results, along with the low productivity and high number of electrons required to incorporate one molecule of a-TTF into the polymer, points to the formation of crosslinked chains. This is consistent with the predominance of b -b linkages into the polymer, as confirmed by IR spectroscopy. Poly(a-TTF) doped with ClO 4 − ions has a very low conductivity, which is ascribed to the low number of polarons present in its monomeric units.