Synthesis and Characterization of Novel Chiral Conjugated Materials

Rajca, Andrzej; Miyasaka, Makoto

doi:10.1002/9783527610266.ch15

Cited by 31 publications

(36 citation statements)

References 143 publications

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“…This research area has developed rapidly, and has been reviewed in book chapters by Rajca and coworkers [33] as well as by Sato and Arai [34]. Whereas azahelicenes and their azonia counterparts (review [35]) have racemization barriers comparable to those of the corresponding helicenes, introduction of 5-membered rings as in the oxa-, thia-, and azathiahelicenes lowers these barriers; oxahelicenes have considerable lower barriers than thiahelicenes with the same number of rings [36].…”

mentioning

confidence: 99%

Heliphenes and Related Structures

Balaban

Vollhardt

2011

TOOCJ

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This review discusses from a qualitative viewpoint three-dimensional structures (hydrocarbons and carbon allotropes) that can be obtained from the 4,6,12-archimedean tiling of the Euclidean plane (graphenylene net) or that are related to subgraphs derived from the graphenylene net, insisting on helical structures called [n]heliphenes with alternating 4-and 6-membered conjugated rings. Analogies with benzenoid [n]helicenes allow proposals for non-planar heliphenerelated structures that have yet to be explored.

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mentioning

confidence: 99%

Heliphenes and Related Structures

Balaban

Vollhardt

2011

TOOCJ

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“…In fact, the central ring in [11]helicene 28 is annulated in a meta fashion and 28 can thus be viewed as a 2,3-disubstituted [6]helicene, hence exhibiting a comparable flexibility. The computational treatment of the barrier revealed that this is a complex conformational process (Fig.…”

Section: Methodsmentioning

confidence: 99%

“…Giving up material monodispersity, Katz et al explored the ways of polymerizing bifunctional helicene units. They succeeded in preparing both optically active [7]helicene-derived cobaltocenium oligomers (15) and the nickel salen [6]helicene-derived conjugated ladder polymer (16). An effort by Katz et al to elongate the helicene backbone stepwise employing a helicene aryne intermediate failed since the unwanted intramolecular Diels-Alder addition prevailed over the intermolecular one (17).…”

Section: An Organometallic Route To Long Helicenesmentioning

confidence: 99%

An organometallic route to long helicenes

Sehnal

Stará̈

Šaman

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

130

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Along with the recent progress in the development of advanced synthetic methods, the chemical community has witnessed an increasing interest in promising carbon-rich materials. Among them, helicenes are unique 3D aromatic systems that are inherently chiral and attractive for asymmetric catalysis, chiral recognition and material science. However, there have been only limited attempts at synthesizing long helicenes, which represent challenging targets. Here, we report on an organometallic approach to the derivatives of undecacyclic helicene, which is based on intramolecular [2 + 2 + 2] cycloisomerization of aromatic hexaynes under metal catalysis closing 6 new cycles of a helicene backbone in a single operation. The preparation of nonracemic compounds relied on racemate resolution or diastereoselective synthesis supported by quantum chemical (density functional theory) calculations. The fully aromatic [11]helicene was studied in detail including the measurement and theoretical calculation of its racemization barrier and its organization on the InSb (001) surface by STM. This research provides a strategy for the synthesis of long helical aromatics that inherently comprise 2 possible channels for charge transport: Along a π-conjugated pathway and across an intramolecularly π-π stacked aromatic scaffold.

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“…Helicenes as unique, inherently chiral 3-D aromatics have been attracting continuous attention for decades [1,2]. In contrast, azahelicenes as their heterocyclic counterparts have remained rather unexplored [3].…”

Section: Introductionmentioning

confidence: 99%

Determination of acid–base dissociation constants of azahelicenes by capillary zone electrophoresis

Ehala

Míšek

Stará̈

et al. 2008

J of Separation Science

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CZE was employed to determine acid-base dissociation constants (pK(a)) of ionogenic groups of azahelicenes in methanol (MeOH). Azahelicenes are unique 3-D aromatic systems, which consist of ortho-fused benzene/pyridine units and exhibit helical chirality. The pK(a) values of pyridinium groups of the studied azahelicenes were determined from the dependence of their effective electrophoretic mobility on pH by a nonlinear regression analysis. The effective mobilities of azahelicenes were determined by CZE at pH range between 2.1 and 10.5. Thermodynamic pK(a) values of monobasic 1-aza[6]helicene and 2-aza[6]helicene in MeOH were determined to be 4.94 +/- 0.05 and 5.68 +/- 0.05, respectively, and pK(a) values of dibasic 1,14-diaza[5]helicene were found to be equal to 7.56 +/- 0.38 and 8.85 +/- 0.26. From these values, the aqueous pK(a) of these compounds was estimated.

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Synthesis and Characterization of Novel Chiral Conjugated Materials

Cited by 31 publications

References 143 publications

Heliphenes and Related Structures

Heliphenes and Related Structures

An organometallic route to long helicenes

Determination of acid–base dissociation constants of azahelicenes by capillary zone electrophoresis

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