Electronic and dynamical effects from the unusual features of the Raman spectra of oligo and polythiophenes

Agosti, E.; Rivola, M.; Hernández, Vı́ctor; Zoppo, M. Del; Zerbi, G.

doi:10.1016/s0379-6779(98)00167-2

Cited by 118 publications

(126 citation statements)

References 31 publications

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“…[46] Raman spectra of both oligoselenophenes and oligothiophenes appear simple, consisting of a few intense bands (Figure 2a). The calculated spectrum of 6 T shows a very similar pattern to that of the experimental spectrum.…”

Section: Energies Of Aromatic Versus Quinoid Structuresmentioning

confidence: 99%

Oligo‐ and Polyselenophenes: A Theoretical Study

Zade

Zamoshchik

Bendikov

2009

Chemistry A European J

138

122

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Recently, a family of conducting polyselenophenes was synthesized, and they were shown to have a number of interesting properties. Here we have studied oligoselenophenes, their cation radicals and dications up to the 50-mer (50 Se), as well as polyselenophene at the B3LYP/6-31G(d) level of theory, and compared them with the corresponding oligothiophenes. Although the calculations reveal many similarities between oligo- and polyselenophenes and their thiophene-based counterparts, they also show the important differences between those two types of conjugated systems. Oligo- and polyselenophenes have a more quinoid character, lower band gap, and importantly, they are more difficult to twist. The theoretical results suggest that the HOMO-LUMO gap (band gap), bond-length alternation (BLA), and charge distribution in oligo- and polyselenophenes are strongly dependent on inter-ring twisting, yet twisting costs little energy. The inter-ring distances in oligo- and polyselenophenes are shorter than the related distances in oligothiophenes, whereas the bond lengths within the selenophene rings are comparable to those of the corresponding oligothiophenes.

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Section: Energies Of Aromatic Versus Quinoid Structuresmentioning

confidence: 99%

Oligo‐ and Polyselenophenes: A Theoretical Study

Zade

Zamoshchik

Bendikov

2009

Chemistry A European J

138

122

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“…[lo51 we have reanalyzed the vibrational assignment based on a very large number of oligomers (-50) and on the basis of the concepts discussed in section 6.4 we concluded that the satellite line must be associated to ring vibrations of the endgroups whose 7r electrons are conjugated with the adjacent thiophene units (at one side) with a distance of interaction decreasing along the chain (in agreement with ref. 105,106) and extending with s = 2-3 thiophene units. While the R mode for thiophene units within the chain does not soften the II mode at either ends shifts because of dynamical and effects.…”

Section: Oligo-and Polythiophenesmentioning

confidence: 99%

Structure and Optical Properties of Conjugated Oligomers from their Vibrational Spectra

Zerbi¹,

Castiglioni²,

Zoppo³

1998

Electronic Materials: The Oligomer Approach

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Traditionally vibrational infrared and Raman spectra are used by synthetic chemists for the simple chemical characterization of materials. Most chemists just give a quick look at the spectrum to judge the success of their synthesis or the chemical purity of the sample. A smaller scientific community has focussed on the more detailed vibrational assignments based on symmetry arguments and/or on isotopic rules for the determination of the molecular shapes and sometimes for the actual measurement of the molecular geometrical parameters. An even smaller community has accounted for the vibrational spectra in terms of molecular dynamics supported by theoretical arguments and by numerical computations.A more modern approach to the understanding of the molecular vibrational spectra is the use of numerical simulations based on 'molecular mechanics' or semiempirical or ab initio quantum mechanical calculations. These calculations have reached a level of automation which we feel is seriously damaging to science when used in an uncritical way.We hope to show that the vibrational spectra of conjugated oligomers and polymers are a very rich source of data which are lost by quick and superficial analysis based on molecular correlations; are a unique source of specific information on the structure and properties of these materials if an attempt is made to go beyond simple diagnosis based on chemical correlations; and are a prototype for the simultaneous use of vibrational frequencies and intensities which carry the understanding of molecular properties to extreme limits.In the past vibrational spectra of conjugated materials have been dealt with both by 'problem oriented' material scientists and by 'technique oriented' molecular spectroscopists. The two approaches are different and the information derived differs in depth and detail. Our aim is to provide material scientists with the technical tools developed by specialized spectroscopists in order to derive unique and specific information on the molecular properties of such technologically relevant materials.First we briefly sketch the physics and the derived vibrational frequency and intensity spectroscopy of chain molecules considered first as ideal infinite and periodic systems and then reduced to realistic finite and possibly disordered molecular systems. The purpose is to provide the reader with the techniques used in spectroscopy for the study of chain molecules and the derived conclusions of general validity. Then we offer an overview of the electronic and optical properties of conjugated oligomers and polymers and present a detailed list of the particular

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“…33 The band around 1400 -1500 cm Ϫ1 is a common feature of Raman spectra of aromatic and heteroaromatic systems; it is always strong and dominates the entire Raman spectrum. [33][34][35][36][37][38][39][40][41] As can be seen in Figure 5(a), the most intense band was located at approximately 1453 cm Ϫ1 and was assigned to the totally symmetric in-phase (CAC) vibration of the bulk thiophene rings spreading over the whole polymer chain. The band at approximately 1490 cm Ϫ1 originated from the antisymmetric stretching modes mostly localized at either end of the polymer chain.…”

mentioning

confidence: 99%

Poly(3‐chlorothiophene) films prepared by the direct electrochemical oxidation of 3‐chlorothiophene in mixed electrolytes of boron trifluoride diethyl etherate and sulfuric acid

Shi

Chen

et al. 2002

J of Applied Polymer Sci

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3-Chlorothiophene (CT) was electrochemically polymerized in mixed electrolytes of a boron trifluoride diethyl etherate solution containing 0 -20% (by volume) sulfuric acid. The oxidation potentials of the monomer in these media were measured to be only 1.06 -1.31 V (vs Ag/AgCl). These values were much lower than that of CT in acetonitrile and 0.1 mol/L (Bu) 4 NBF 4 (1.92 V vs Ag/AgCl). Poly(3-chlorothiophene) (PCT) films with conductivities of 0.1-2 S cm Ϫ1 were obtained. The structure, morphology, and electrochemical behavior of the PCT films also were investigated.

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Electronic and dynamical effects from the unusual features of the Raman spectra of oligo and polythiophenes

Cited by 118 publications

References 31 publications

Oligo‐ and Polyselenophenes: A Theoretical Study

Oligo‐ and Polyselenophenes: A Theoretical Study

Structure and Optical Properties of Conjugated Oligomers from their Vibrational Spectra

Poly(3‐chlorothiophene) films prepared by the direct electrochemical oxidation of 3‐chlorothiophene in mixed electrolytes of boron trifluoride diethyl etherate and sulfuric acid

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