Electronic absorption and Raman studies of BF4−-doped polythiophene based on the spectra of the radical cation and dication of α-sexithiophene

Yokonuma, Nami; Furukawa, Yukio; Tasumi, Mitsuo; Kuroda, Masami; Nakayama, Juzo

doi:10.1016/0009-2614(96)00383-1

Cited by 93 publications

(128 citation statements)

References 23 publications

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“…These spectra were identical to those measured by Yokonuma et al in dichloromethane using iron chloride. 28 The Raman spectrum of 6T ·+ has the same pattern as the styryl sexithiophene radical cations, with the most intense band located at 1440 cm −1 . The thiophene CH bending modes at 1067 and 1055 cm −1 are downshifted from that of the styryl sexithiophenes' ͑1085 cm −1 ͒.…”

Section: Solution State Oxidized Speciesmentioning

confidence: 95%

The effect of oxidation on the structure of styryl-substituted sexithiophenes: A resonance Raman spectroscopy and density functional theory study

Clarke

Gordon

Officer

et al. 2006

The Journal of Chemical Physics

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The structures and vibrational properties of a series of styryl-substituted sexithiophenes and their charged species have been examined using resonance Raman spectroscopy in conjunction with density functional theory calculations. The calculated geometries of the radical cations and dications indicate that the quinoidal charged defects are more strongly localized in the center of the thiophene backbone than is observed in other sexithiophenes. This defect confinement, induced by the positions of the styryl substituents, is particularly evident in the dication species. However, the defect confinement weakens when alkoxy groups are added onto the phenyl rings by causing the extension of the charged defect into the styryl groups. The Raman spectra of the neutral styryl sexithiophenes are dominated by intense thiophene symmetrical stretching modes in both the measured and predicted spectra. Oxidation generates radical cations and dications, both of which can be observed in the solution state resonance Raman spectra. Unlike other sexithiophenes, which generally show a downshift of the intense thiophene stretching mode from the radical cation to the dication, a small upshift is observed for the styryl-substituted sexithiophenes. The theoretical spectra predict an insignificant change during this transition and the eigenvector for this mode reveals that it is localized over the same area occupied by the confined defect. In contrast, the solid state resonance Raman spectra of electrochemically oxidized films reveal evidence of solely radical cations and there is an appreciable downshift of the intense thiophene stretching mode compared with the corresponding mode in the solution spectra. This implies that the increase in the effective conjugation length from the solution to the solid state is greater for the radical cations than for the neutral species. It therefore appears that the radical cations form pi stacks in the solid film and the resulting intermolecular interactions effectively allow a further extension of the electron delocalization.

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Section: Solution State Oxidized Speciesmentioning

confidence: 95%

The effect of oxidation on the structure of styryl-substituted sexithiophenes: A resonance Raman spectroscopy and density functional theory study

Clarke

Gordon

Officer

et al. 2006

The Journal of Chemical Physics

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“…13,14 The usefulness of Raman spectroscopy in the characterization of conjugational defects in -conjugated materials has been largely demonstrated by Furukawa et al in the past few years. [15][16][17][18][19] The power and selectivity of the Raman characterization of doped conjugated polymers is enhanced by using exciting laser lines in resonance with the optical bands appearing in the NIR region. These authors have developed a so-called ''oligomeric approach'' to rationalize the Raman spectra of doped polymers, which is based on the synthesis of charged oligomers, that were regarded as models for localized excitations.…”

Section: Introductionmentioning

confidence: 99%

Vibrational spectra of charged defects in a series of α,α′-dimethyl end-capped oligothiophenes induced by chemical doping with iodine

Casado

Hernández

Hotta

et al. 1998

The Journal of Chemical Physics

112

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We present the results of a detailed study carried out on a few α,α′-dimethyl end-capped oligothiophenes which have been in situ doped with dry iodine vapors, at different concentrations. The doping process of these well sized oligomers (from dimer to hexamer) has been monitored by using Fourier transform infrared absorption and Fourier transform raman scattering spectroscopies. These data, when combined with the vibrational full assignment of the oligomers in the neutral state and the electronic absorption bands recorded for both neutral and doped compounds, provide a complete spectroscopic characterization of a full series of positive polaron-type model defects of doped polythiophene. We have also performed density functional theory quantum-chemical calculations in order to analyze the effects of ionization on the geometries and vibrational spectra of these systems.

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“…73,74 The similarities include numerous bands in the 1100-1550 cm -1 region that are significantly enhanced compared with ground-state oligothiophenes that have all aromatic rings. 48,[72][73][74] The dications for short oligomers are described by a bipolaron structure, which has a quinoidal region bordered on each side by positive charge centers. 46,52,75,76 Results from DFT calculations (Figure 3) show that the dication and the T 1 states of the hexamer share some structural features.…”

mentioning

confidence: 99%

Resonance Raman Spectroscopy of the T₁ Triplet Excited State of Oligothiophenes

Wang

Angelella

Doyle

et al. 2015

J. Phys. Chem. Lett.

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The characterization of triplet excited states is essential for research on organic photovoltaics and singlet fission. We report resonance Raman spectra of two triplet oligothiophenes with n-alkyl substituents, a tetramer and hexamer. The spectra of the triplets are more complex than the ground state, and we find that density functional theory calculations are a useful starting point for characterizing the bands. The spectra of triplet tetrathiophene and hexathiophene differ significantly from one another. This observation is consistent with a T1 excitation that is delocalized over at least five rings in long oligomers. Bands in the 500-800 cm(-1) region are greatly diminished for an aggregated sample of hexathiophene, likely caused by fast electronic dephasing. These experiments highlight the potential of resonance Raman spectroscopy to unequivocally detect and characterize triplets in thiophene materials. The vibrational spectra can also serve as rigorous standards for evaluating computational methods for excited-state molecules.

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Electronic absorption and Raman studies of BF4−-doped polythiophene based on the spectra of the radical cation and dication of α-sexithiophene

Cited by 93 publications

References 23 publications

The effect of oxidation on the structure of styryl-substituted sexithiophenes: A resonance Raman spectroscopy and density functional theory study

The effect of oxidation on the structure of styryl-substituted sexithiophenes: A resonance Raman spectroscopy and density functional theory study

Vibrational spectra of charged defects in a series of α,α′-dimethyl end-capped oligothiophenes induced by chemical doping with iodine

Resonance Raman Spectroscopy of the T₁ Triplet Excited State of Oligothiophenes

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Electronic absorption and Raman studies of BF4−-doped polythiophene based on the spectra of the radical cation and dication of α-sexithiophene

Cited by 93 publications

References 23 publications

The effect of oxidation on the structure of styryl-substituted sexithiophenes: A resonance Raman spectroscopy and density functional theory study

The effect of oxidation on the structure of styryl-substituted sexithiophenes: A resonance Raman spectroscopy and density functional theory study

Vibrational spectra of charged defects in a series of α,α′-dimethyl end-capped oligothiophenes induced by chemical doping with iodine

Resonance Raman Spectroscopy of the T1 Triplet Excited State of Oligothiophenes

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Resonance Raman Spectroscopy of the T₁ Triplet Excited State of Oligothiophenes