Does the donor–acceptor concept work for designing synthetic metals?

Salzner, Ulrike; Karalti, Ozan; Durdaği, Serdar

doi:10.1007/s00894-005-0046-2

Cited by 53 publications

(38 citation statements)

References 47 publications

(53 reference statements)

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“…This basis set has been tested extensively and has been shown to yield reliable results for geometries and excited states of neutral polyenes as well as other conjugated oligomers. 43,[51][52][53][54] As cations and excited states of cations have compact electron densities, 15 this basis set is sufficient for all properties of interest in the present investigation.…”

Section: Methodsmentioning

confidence: 99%

Theoretical Investigation of Excited States of Large Polyene Cations as Model Systems for Lightly Doped Polyacetylene

Salzner

2006

J. Chem. Theory Comput.

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Electronic excitations of polyene cations with chain lengths of up to 101 CH units were investigated as model systems for lightly doped polyacetylene (PA). Since high level ab initio calculations such as complete active space perturbation theory (CASPT2) are limited to systems with about 14 CH units, the performances of time-dependent Hartree-Fock (TDHF) and time-dependent density functional theory (TDDFT) were evaluated. It turned out that TDDFT excitations energies are much more accurate for polyene cations than for neutral polyenes. The difference between TDHF and TDDFT excitation energies for the first allowed excited state of C 49 H 51 + is only 0.30 eV with pure DFT and 0.21 eV with a hybrid functional. For open-shell systems, pure DFT is found to be superior to DFT-hybrid functionals because it does not suffer from spin-contamination. Pure TDDFT excitation energies and oscillator strengths for small openshell polyene cations compare well with high level ab initio results. Excitation energies are found to be almost independent of the geometry, i.e., the size of the defect. Localization of the defect, however, shifts oscillator strengths from the HOMO-LUMO transition to higher lying excited states of the same symmetry. Lightly doped PA is predicted to exhibit several strong absorptions below 1 eV.

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Section: Methodsmentioning

confidence: 99%

Theoretical Investigation of Excited States of Large Polyene Cations as Model Systems for Lightly Doped Polyacetylene

Salzner

2006

J. Chem. Theory Comput.

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“…Both studies confirm the saturation of the lowest transition energies for very long oligomers, in accordance with previous investigations (see Section 2.2); they also stress the different conditions for the calculations (single chains in the gas phase) and for the experiments (solid-state phase). While Salzner et al [118] estimate the geometry relaxation, solvent, and solidstate effects, Zade and Bendikov [119] do not address their impact, thus claiming too fast an accurate prediction of the experimental optical gap; in addition, their B3LYP/6-31G* calculations yield a much too low value of 2.0 eV. The calculated transition energy obtained by Salzner et al [118] for the polymer using the B3P86-30% functional (E vert = 2.5 eV) is in much better agreement with experiment; however, this is a result of the fact that their calculated values for short oligomers are far too large.…”

Section: Note Added In Proofmentioning

confidence: 97%

“…While Salzner et al [118] estimate the geometry relaxation, solvent, and solidstate effects, Zade and Bendikov [119] do not address their impact, thus claiming too fast an accurate prediction of the experimental optical gap; in addition, their B3LYP/6-31G* calculations yield a much too low value of 2.0 eV. The calculated transition energy obtained by Salzner et al [118] for the polymer using the B3P86-30% functional (E vert = 2.5 eV) is in much better agreement with experiment; however, this is a result of the fact that their calculated values for short oligomers are far too large. Thus, the strong overestimation of the slope in the 1/N representation with standard DFT methods, as stated in Section 4.2, also applies for these recent calculations.…”

Section: Note Added In Proofmentioning

confidence: 97%

“…[118,119] In both papers, TD-DFT calculations on long oligothiophenes with up to 40 units were performed. Both studies confirm the saturation of the lowest transition energies for very long oligomers, in accordance with previous investigations (see Section 2.2); they also stress the different conditions for the calculations (single chains in the gas phase) and for the experiments (solid-state phase).…”

Section: Note Added In Proofmentioning

confidence: 99%

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Optical Bandgaps of π‐Conjugated Organic Materials at the Polymer Limit: Experiment and Theory

2007

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In this Review, the extreme care that must be taken when predicting the optical properties of conjugated polymers via the oligomer approach, and when comparing theoretical and experimental data, is illustrated. In the first part, conceptual strategies for the correct determination of optical transitions from experimental spectra and relevant extrapolation procedures at the polymer limit are introduced. The impact of conformational, substitution, solvent, and solid‐state effects on the optical properties is discussed in light of experimental data reported for molecular backbones based on phenylene, phenylenevinylene, and thiophene repeat units. A comparison is then made between experimental results and those provided by standard quantum‐chemical methods, to assess their reliability.

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“…[25][26][27] It has frequently been considered as a reasonable approach throughout the literature looking to provide an origin for the relatively unconventionnal dual-band optical spectra. 4,6,7 Extending the Concept to the Synthesis of Broadly Absorbing Chromophores By "Filling" the Dual-Band Polymer Absorption with a Complementary Spectrum.…”

Section: Spectral Engineering In π-Conjugated Polymersmentioning

confidence: 99%

Spectral Engineering in π-Conjugated Polymers with Intramolecular Donor−Acceptor Interactions

2010

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With the development of light-harvesting organic materials for solar cell applications and molecular systems with fine-tuned colors for nonemissive electrochromic devices (e.g., smart windows, e-papers), a number of technical challenges remain to be overcome. Over the years, the concept of "spectral engineering" (tailoring the complex interplay between molecular physics and the various optical phenomena occurring across the electromagnetic spectrum) has become increasingly relevant in the field of π-conjugated organic polymers. Within the spectral engineering toolbox, the "donor-acceptor" approach uses alternating electron-rich and electron-deficient moieties along a π-conjugated backbone. This approach has proved especially valuable in the synthesis of dual-band and broadly absorbing chromophores with useful photovoltaic and electrochromic properties. In this Account, we highlight and provide insight into a present controversy surrounding the origin of the dual band of absorption sometimes encountered in semiconducting polymers structured using the "donor-acceptor" approach. Based on empirical evidence, we provide some schematic representations to describe the possible mechanisms governing the evolution of the two-band spectral absorption observed on varying the relative composition of electron-rich and electron-deficient substituents along the π-conjugated backbone. In parallel, we draw attention to the choice of the method employed to estimate and compare the absorption coefficients of polymer chromophores exhibiting distinct repeat unit lengths, and containing various extents of solubilizing side-chains along their backbone. Finally, we discuss the common assumption that "donor-acceptor" systems should have systematically lower absorption coefficients than their "all-donor" counterparts. The proposed models point toward important theoretical parameters which could be further explored at the macromolecular level to help researchers take full advantage of the complex interactions taking place in π-conjugated polymers with intramolecular "donor-acceptor" characteristics.

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Does the donor–acceptor concept work for designing synthetic metals?

Cited by 53 publications

References 47 publications

Theoretical Investigation of Excited States of Large Polyene Cations as Model Systems for Lightly Doped Polyacetylene

Theoretical Investigation of Excited States of Large Polyene Cations as Model Systems for Lightly Doped Polyacetylene

Optical Bandgaps of π‐Conjugated Organic Materials at the Polymer Limit: Experiment and Theory

Spectral Engineering in π-Conjugated Polymers with Intramolecular Donor−Acceptor Interactions

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