Synthesis and Properties of Cationic π-Conjugated Systems Stabilized by Bicyclo[2.2.2]octene Units

Komatsu, Kôichi; Nishinaga, Tohru

doi:10.1055/s-2004-837217

Cited by 31 publications

(17 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Studies to reveal the properties of non‐aggregated oligothiophene cations have been conducted by introducing bulky groups at the β‐positions of thiophene rings to inhibit intermolecular interactions 23. We are also interested in cationic oligothiophenes,24, 25 and in our previous study, we achieved the first systematic X‐ray analysis of single crystals of cationic oligothiophenes25b,e annelated with bicyclo[2.2.2]octene (BCO) groups 25c. Among them, the fully BCO‐annelated oligothiophene 1 ( n T) radical cations and dications showed segregated structures in the solid state 25b.…”

Section: Introductionmentioning

confidence: 99%

Steric Control in the π‐Dimerization of Oligothiophene Radical Cations Annelated with Bicyclo[2.2.2]octene Units

Tateno

Takase

Iyoda

et al. 2013

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

A Two series of oligothiophenes 2(nT) (n=4,5), annelated with bicyclo[2.2.2]octene (BCO) units at both ends, and quaterthiophenes 3 a-c, annelated with various numbers of BCO units at different positions, were newly synthesized to investigate the driving forces of π-dimerization and the structure-property relationships of the π-dimers of oligothiophene radical cations. Their radical-cation salts were prepared through chemical one-electron oxidation by using nitrosonium hexafluoroantimonate. From variable-temperature electron spin resonance and electronic absorption measurements, the π-dimerization capability was found to vary among the members of the 2(nT)(+)(·)SbF6(-) series and 3(+)(·)SbF6(-) series of compounds. To examine these results, density functional theory (DFT) calculations at the M06-2X/6-31G(d) level were conducted for the π-dimers. This level of theory was found to successfully reproduce the previously reported X-ray structure of (2(3T))2(2+) having a bent π-dimer structure with cis-cis conformations. The absorption bands obtained by time-dependent DFT calculations for the π-dimers were in reasonable agreement with the experimental spectra. The attractive and repulsive forces for the π-dimerization were divided into four factors: 1) SOMO-SOMO interactions, 2) van der Waals forces, 3) solvation, and 4) Coulomb repulsion, and the effects of each factor on the structural differences and chain-length dependence are discussed in detail.

show abstract

Section: Introductionmentioning

confidence: 99%

Steric Control in the π‐Dimerization of Oligothiophene Radical Cations Annelated with Bicyclo[2.2.2]octene Units

Tateno

Takase

Iyoda

et al. 2013

Chemistry A European J

Self Cite

View full text Add to dashboard Cite

show abstract

“…This structural modification was expected to not only inhibit the possible intermolecular interaction [18], which would make the interpretation of observed spectra complex, but also to be quite effective for stabilization of the cationic π-systems [19]. Thus, we succeeded in the first systematic X-ray structural analysis of cationic oligothiophenes, i.e., radical cation and dication salts of 1 (nT) (n = 2, 3, 4, 6) [17].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Properties of Octithiophene Dication Sterically Segregated by Annelation with Bicyclo[2.2.2]octene Units

et al. 2010

Self Cite

View full text Add to dashboard Cite

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.

show abstract

“…Such effects, However, are regarded to be rather weak to become a major factor for cation stabilization, except in such a special case as cyclopropyl conjugation, which is highly effective owing to a large p-character in the strained C-C single bonds. In this article, we wish to show that such σ-π conjugation effect exerted by strain-free C-C bonds typically of bicyclo [2.2.2]octene can become significant in cation stabilization when the effects are accumulated in properly constructed molecular structures (1,2,3). This effect together with the steric protection by the bicyclic frameworks is, in fact, quite advantageous, allowing the formation of a wide range of novel cyclic π-conjugated systems bearing positive charge, which could not have been realized by other means.…”

Section: Introductionmentioning

confidence: 99%

“…The observed lengths (A) ofCl-S andCl-C2 in 2rSbF 6~ are 1.72(1) and 1.31(2) to be compared with 1.324(3) and 1.760(2) determined for neutral 21, respectively. Also shown is the thianthrene radical cation 23' + .…”

mentioning

confidence: 99%

Super-Stabilization of π-Conjugated Cations by Annelation to Bicyclic Frameworks

Komatsu

2007

ACS Symposium Series

Self Cite

View full text Add to dashboard Cite

As exemplified by the synthesis of the extraordinarily stable tropylium ion, the annelation of cyclic π-conjugated cations with rigid σ-framework, bicyclo[2.2.2]octene, has been found to be an effective method for creation of unusually stable cationic π-conjugated systems. By using this method, detailed X-ray crystallographic studies have been conducted for the monomeric radical-cation salts of hydrocarbons such as cyclooctatetraene and a series of benzenoid condensed aromatics and of sulfur containing compounds such as thiophene, dithiins, and oligothiophenes. Some of these species can be further oxidized to dications, and also undergo intriguing rearrangements to cationic species with novel structures. The results are well interpreted by the use of theoretical calculations. 32

show abstract

Synthesis and Properties of Cationic π-Conjugated Systems Stabilized by Bicyclo[2.2.2]octene Units

Cited by 31 publications

References 35 publications

Steric Control in the π‐Dimerization of Oligothiophene Radical Cations Annelated with Bicyclo[2.2.2]octene Units

Steric Control in the π‐Dimerization of Oligothiophene Radical Cations Annelated with Bicyclo[2.2.2]octene Units

Synthesis and Properties of Octithiophene Dication Sterically Segregated by Annelation with Bicyclo[2.2.2]octene Units

Super-Stabilization of π-Conjugated Cations by Annelation to Bicyclic Frameworks

Contact Info

Product

Resources

About