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Conjugated Oligomers
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Conjugated Oligomers

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (31 January 2010) | Viewed by 84837

Special Issue Editor

Prof. Dr. Herbert Meier

E-Mail Website
Guest Editor
Institut für Organische Chemie, Duesbergweg 10-14 Johannes Gutenberg-Universität, 55099 Mainz, Germany
Interests: conjugated oligomers and polymers and their application in photoconductivity and nonlinear optics; synthesis of stilbenoid dendrimers; squaraines with extended conjugation; optical switching with liquid crystals; areno-condensed annulenes and their application as liquid crystals and photoconductors; new syntheses in heterocyclic chemistry

Special Issue Information

Dear Colleagues,

Monodisperse, conjugated oligomers attract increasing attention in chemistry and materials science because of their interesting electrical, optical, and optoelectronic properties. These compounds can serve as materials in their own right but also as model compounds for the corresponding conjugated polymers.

The idea to extrapolate a certain property P(n) for increasing numbers n of repeat units to a limiting value P∞ (n → ∞) is fascinating. The convergence, however, is not always simple. The effective conjugation length nECL shall give an answer to the question from which n on a further extension of the chain does not any longer affect a certain property P─ for example the HOMO-LUMO gap/ band gap in the solid state DE(n), the fluorescence quantum yield ФF(n), etc.

The structural homogeneity of monodisperse, conjugated oligomers with a well defined chain length and selected end groups facilitates the study of these compounds (nanoparticles) and gives rise to an excellent reproducibility of a certain behavior.

The present special issue of this journal shall give an impression of some modern aspects and recent developments in the chemistry of conjugated oligomers and their applications.

Prof. Dr. Herbert Meier
Guest Editor

Keywords

  • Electrical conductance of conjugated oligomers
  • Photoluminescence and electroluminescence
  • Nonlinear optics
  • Generation and mobility of charge carriers
  • Energy and/or electron transfer
  • Oligo(ethynediylporphyrindiylethynediyl)s

Published Papers (7 papers)

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Research

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496 KiB  
Article
Synthesis and Properties of Octithiophene Dication Sterically Segregated by Annelation with Bicyclo[2.2.2]octene Units
by Tohru Nishinaga, Daisuke Yamazaki, Masaki Tateno, Masahiko Iyoda and Koichi Komatsu
Materials 2010, 3(3), 2037-2052; https://doi.org/10.3390/ma3032037 - 19 Mar 2010
Cited by 17 | Viewed by 9450
Abstract
Octithiophene sterically segregated by annelation with bicyclo[2.2.2]octene (BCO) units was synthesized to study the unimolecular properties of longer oligothiophene dications. For the preparation of such longer oligomers, a new route for the synthesis of the monomer annelated with BCO unit at the 3,4-positions [...] Read more.
Octithiophene sterically segregated by annelation with bicyclo[2.2.2]octene (BCO) units was synthesized to study the unimolecular properties of longer oligothiophene dications. For the preparation of such longer oligomers, a new route for the synthesis of the monomer annelated with BCO unit at the 3,4-positions of thiophene ring was developed. Attempted synthesis of octithiophene 1(8T) fully annelated with BCO units was hampered by low solubility of the product, and octithiophene 2(8T) having octyl groups instead of the BCO units at the second rings from the both ends of 1(8T) was synthesized to solve the solubility problem. Neutral 2(8T) has a lower planarity due to the steric repulsion between the octyl substituents and the neighboring thiophene units. However, dication 2(8T)2+, which was obtained as a stable salt by chemical two-electron oxidation with NO+SbF6-, has a planar quinoid structure, as judged from a linear correlation between the inverse chain length and the absorption energy for 1(nT)2+ (n = 3,4,6) and 2(8T)2+. Based on the comparison with the calculated absorption spectra and the result of ESR inactive properties, 2(8T)2+ appears to have a singlet ground state with open-shell biradical character rather than a closed-shell singlet structure. Full article
(This article belongs to the Special Issue Conjugated Oligomers)
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306 KiB  
Communication
Charge-Transfer Controlled Crystallization of a Model Oligomer for Donor-Acceptor-Polythiophenes
by Ralph Rieger, Volker Enkelmann and Klaus Müllen
Materials 2010, 3(3), 1904-1912; https://doi.org/10.3390/ma3031904 - 17 Mar 2010
Cited by 7 | Viewed by 8909
Abstract
A model donor-acceptor oligomer consisting of benzodithiophene-diketone and thiophene has been investigated with regard to its molecular packing and opto-electronic properties. The crystal structure suggests that the packing is dominated by charge-transfer interactions between the electron-rich part of the molecule and the electron-poor [...] Read more.
A model donor-acceptor oligomer consisting of benzodithiophene-diketone and thiophene has been investigated with regard to its molecular packing and opto-electronic properties. The crystal structure suggests that the packing is dominated by charge-transfer interactions between the electron-rich part of the molecule and the electron-poor part. A series of observations corroborate this assumption, among them are a charge-transfer band in the film absorption spectra and exceptionally low π-π distances. A detailed analysis of the energetic levels of the present system reveals that only the HOMO level of the acceptor is shifted by conjugation to the donor. The results can contribute to the development of improved materials for organic electronics. Full article
(This article belongs to the Special Issue Conjugated Oligomers)
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Review

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1151 KiB  
Review
Prediction of Excitation Energies for Conjugated Oligomers and Polymers from Time-Dependent Density Functional Theory
by Jianmin Tao, Sergei Tretiak and Jian-Xin Zhu
Materials 2010, 3(5), 3430-3467; https://doi.org/10.3390/ma3053430 - 24 May 2010
Cited by 5 | Viewed by 10280
Abstract
With technological advances, light-emitting conjugated oligomers and polymers have become competitive candidates in the commercial market of light-emitting diodes for display and other technologies, due to the ultralow cost, light weight, and flexibility. Prediction of excitation energies of these systems plays a crucial [...] Read more.
With technological advances, light-emitting conjugated oligomers and polymers have become competitive candidates in the commercial market of light-emitting diodes for display and other technologies, due to the ultralow cost, light weight, and flexibility. Prediction of excitation energies of these systems plays a crucial role in the understanding of their optical properties and device design. In this review article, we discuss the calculation of excitation energies with time-dependent density functional theory, which is one of the most successful methods in the investigation of the dynamical response of molecular systems to external perturbation, owing to its high computational efficiency. Full article
(This article belongs to the Special Issue Conjugated Oligomers)
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1218 KiB  
Review
Star-Shaped Conjugated Systems
by Heiner Detert, Matthias Lehmann and Herbert Meier
Materials 2010, 3(5), 3218-3330; https://doi.org/10.3390/ma3053218 - 19 May 2010
Cited by 100 | Viewed by 17089
Abstract
The present review deals with the preparation and the properties of star-shaped conjugated compounds. Three, four or six conjugated arms are attached to cross-conjugated cores, which consist of single atoms (B, C+, N), benzene or azine rings or polycyclic ring systems, [...] Read more.
The present review deals with the preparation and the properties of star-shaped conjugated compounds. Three, four or six conjugated arms are attached to cross-conjugated cores, which consist of single atoms (B, C+, N), benzene or azine rings or polycyclic ring systems, as for example triphenylene or tristriazolotriazine. Many of these shape-persistent [n]star compounds tend to π-stacking and self-organization, and exhibit interesting properties in materials science: Linear and non-linear optics, electrical conductivity, electroluminescence, formation of liquid crystalline phases, etc. Full article
(This article belongs to the Special Issue Conjugated Oligomers)
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368 KiB  
Review
A Brief Review of Chelators for Radiolabeling Oligomers
by Yuxia Liu, Guozheng Liu and Donald J. Hnatowich
Materials 2010, 3(5), 3204-3217; https://doi.org/10.3390/ma3053204 - 14 May 2010
Cited by 28 | Viewed by 9781
Abstract
The chemical modification of oligomers such as DNA, PNA, MORF, LNA to attach radionuclides for nuclear imaging and radiotherapy applications has become a field rich in innovation as older methods are improved and new methods are introduced. This review intends to provide a [...] Read more.
The chemical modification of oligomers such as DNA, PNA, MORF, LNA to attach radionuclides for nuclear imaging and radiotherapy applications has become a field rich in innovation as older methods are improved and new methods are introduced. This review intends to provide a brief overview of several chelators currently in use for the labeling of oligomers with metallic radionuclides such as 99mTc, 111In and 188Re. While DNA and its analogs have been radiolabeled with important radionuclides of nonmetals such as 32P, 35S, 14C, 18F and 125I, the labeling methods for these isotopes involve covalent chemistry that is quite distinct from the coordinate-covalent chelation chemistry described herein. In this review, we provide a summary of the several chelators that have been covalently conjugated to oligomers for the purpose of radiolabeling with metallic radionuclides by chelation and including details on the conjugation, the choice of radionuclides and labeling methods. Full article
(This article belongs to the Special Issue Conjugated Oligomers)
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1114 KiB  
Review
Oligomers and Polymers Based on Pentacene Building Blocks
by Dan Lehnherr and Rik R. Tykwinski
Materials 2010, 3(4), 2772-2800; https://doi.org/10.3390/ma3042772 - 14 Apr 2010
Cited by 25 | Viewed by 13624
Abstract
Functionalized pentacene derivatives continue to provide unique materials for organic semiconductor applications. Although oligomers and polymers based on pentacene building blocks remain quite rare, recent synthetic achievements have provided a number of examples with varied structural motifs. This review highlights recent work in [...] Read more.
Functionalized pentacene derivatives continue to provide unique materials for organic semiconductor applications. Although oligomers and polymers based on pentacene building blocks remain quite rare, recent synthetic achievements have provided a number of examples with varied structural motifs. This review highlights recent work in this area and, when possible, contrasts the properties of defined-length pentacene oligomers to those of mono- and polymeric systems. Full article
(This article belongs to the Special Issue Conjugated Oligomers)
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609 KiB  
Review
Non-Traditional Aromatic Topologies and Biomimetic Assembly Motifs as Components of Functional Pi-Conjugated Oligomers
by John D. Tovar, Stephen R. Diegelmann and Patricia A. Peart
Materials 2010, 3(2), 1269-1280; https://doi.org/10.3390/ma3021269 - 23 Feb 2010
Cited by 3 | Viewed by 14630
Abstract
This article will highlight our recent work using conjugated oligomers as precursors to electroactive polymer films and self-assembling nanomaterials. One area of investigation has focused on nonbenzenoid aromaticity in the context of charge delocalization in conjugated polymers. In these studies, polymerizable pi-conjugated units [...] Read more.
This article will highlight our recent work using conjugated oligomers as precursors to electroactive polymer films and self-assembling nanomaterials. One area of investigation has focused on nonbenzenoid aromaticity in the context of charge delocalization in conjugated polymers. In these studies, polymerizable pi-conjugated units were coupled onto unusual aromatic cores such as methano[10]annulene. This article will also show how biologically-inspired assembly of molecularly well-defined oligopeptides that flank pi-conjugated oligomers has resulted in the aqueous construction of 1-dimensional nanomaterials that encourage electronic delocalization among the pi-electron systems. Full article
(This article belongs to the Special Issue Conjugated Oligomers)
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