Majority Rules in the Copolymerization of Mirror Image Isomers

Green, Mark M.; Garetz, Bruce A.; Munoz, B. C.; Chang, He Ping; Hoke, Steven H.; Cooks, R. Graham

doi:10.1021/ja00119a039

Cited by 371 publications

(336 citation statements)

References 2 publications

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“…Therefore, the minority enantiomers are in part forced into a less-favored situation by the majority. Hence, this scenario fits rather the ''majority rule'' scenario reported for helical polymers [157].…”

Section: Diastereomers and Diastereomeric Recognitionsupporting

confidence: 84%

“…With chiral bias, on the other hand, some of these processes will have a defined enantiospecific outcome. This has been shown by Green et al [156,157] for helical polyisocyanate polymers with short aliphatic side chains. These show an equal probability for left-and right-handed helicity, giving them overall a zero optical activity.…”

Section: Diastereomers and Diastereomeric Recognitionsupporting

confidence: 60%

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Molecular chirality at surfaces

Ernst

2012

Physica Status Solidi (b)

221

264

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With the adsorption of larger molecules being increasingly tackled by surface scientists, the aspect of chirality often plays a role. This paper gives a topical review of molecular chirality at surfaces and gives a phenomenological overview of different aspects of adsorption and self‐assembly of chiral and prochiral molecules and the principles of mirror‐symmetry breaking at a surface. After a brief introduction into the history of molecular chirality and the important role it played for understanding the spatial structure of molecules, definitions of chirality are presented. Topics treated here are principle ways to create single chiral adsorbates, chiral ensembles, and monolayers by achiral molecules, adsorption of intrinsically chiral molecules at achiral and chiral surfaces, long‐range symmetry breaking in two‐dimensional (2D) crystals due to additional chiral bias, chiral restructuring of solid surfaces under the influence of chiral molecules, switching the handedness of adsorbates, and chirality at the liquid/air interface. An outlook onto further potential research directions and recommendations for further reading, including nonsurface‐related sources of chiral topics completes this paper.

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Section: Diastereomers and Diastereomeric Recognitionsupporting

confidence: 84%

Section: Diastereomers and Diastereomeric Recognitionsupporting

confidence: 60%

Molecular chirality at surfaces

Ernst

2012

Physica Status Solidi (b)

221

264

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“…The majority-rule principle has been studied extensively for covalently bonded helical polymers both from experimental and theoretical viewpoints (34)(35)(36). However, to our knowledge, examples of chirality amplification governed by the majority rule have never been reported for noncovalent, supramolecular polymers and assemblies (37,38).…”

Section: Resultsmentioning

confidence: 99%

Self-assembled graphitic nanotubes with one-handed helical arrays of a chiral amphiphilic molecular graphene

Jin

Fukushima²,

Niki³

et al. 2005

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

262

177

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Self-assembly of a Gemini-shaped, chiral amphiphilic hexa-perihexabenzocoronene having two chiral oxyalkylene side chains, along with two lipophilic side chains, yields graphitic nanotubes with one-handed helical chirality. The nanotubes are characterized by an extremely high aspect ratio of >1,000 and have a uniform diameter of 20 nm and a wall thickness of 3 nm. The nanotubes with right-and left-handed helical senses were obtained from the (S)-and (R)-enantiomers of the amphiphile, respectively, due to an efficient translation of point chirality into supramolecular helical chirality. The (S)-and (R)-enantiomers coassemble at varying mole ratios to give nanotubes, whose circular dichroism profiles are almost unchanged over a wide range of the enantiomeric excess of the amphiphile (100 -20%). The high level of chirality amplification thus observed indicates a long-range cooperativity in the selfassembling process. In sharp contrast, a hexabenzocoronene amphiphile with chiral lipophilic side chains did not form nanotubular assemblies. The present work demonstrates the majority rule in noncovalent systems and also may provide a synthetic strategy toward realization of molecular solenoids. chirality ͉ self-assembly H elicity is one of the most essential structural elements for certain biomolecules such as peptides and DNA. The prominent functions of these biological components have motivated chemists to design artificial helical architectures (1-8), which can be used for a variety of applications such as chiral separation (9, 10) and sensing (11-15), asymmetric synthesis (16), liquid crystals (17-19), nonlinear optics (20, 21), and so forth. Recently, a hot issue of chirality has emerged in relation to the helicity of the hexagonal carbon lattice in carbon nanotubes, because it determines the conductive properties of carbon nanotubes (22-24). Conductive polymers with helical architectures (25) also have attracted attention in view of the concept of molecular solenoids (26,27), although this concept has yet been a dream of scientists, because there are no molecular objects that fulfill certain requisites for conductivity and helicity. Here, we report an example of conductive tubular objects consisting of one-handed helical arrays of a -stacked chiral molecular graphene. Self-assembly of hexa-peri-hexabenzocoronene (HBC) derivatives to form discotic liquid crystals and nanofibers has been studied extensively by Müllen and coworkers (28,29). We recently found that an amphiphilic HBC derivative (1) (Fig. 1) self-assembles in polar organic solvents such as tetrahydrofuran (THF) to give graphitic nanotubes, whose wall consists of a bilayer tape formed from bilaterally coupled columns of -stacked HBC units (30). In the course of this work, we have noticed that the self-assembly of 1, although achiral, gives a mixture of coiled and tubular assemblies under certain conditions, suggesting that the tubular objects also bear a helical structural element. This observation prompted us to design chiral HBC amphiphiles 2 and 3 (Fi...

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“…As a consequence, they consist of interconvertible right-and lefthanded helical segments separated by rarely occurring helical reversals, as demonstrated by Green et al, 6,20,21 so that a preferred-handed helical conformation can be induced in the presence of a small amount of chiral residues at the pendant 6 or terminal ends 22,23 or a noncovalently interacting stimulant, 24 with their helical senses being determined under thermodynamic control. Either static or dynamic helical polymers with an excess one-handedness, such as poly(quinoxaline-2,3-diyl)s (4), 25,26 polyguanidines (5), 27,28 poly(phenyl isocyanide)s (6) 29,30 and polyacetylenes (7), [8][9][10][11][12][31][32][33][34] have also been prepared by the polymerization of analogous monomers bearing different chiral or achiral substituents, that is, the boundary between static and dynamic helical conformations is totally dependent on the helix inversion barrier.…”

mentioning

confidence: 99%

Synthesis and structure determination of helical polymers

Yashima

2010

Polym J

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During the last decade, remarkable progress in developing synthetic helical polymers with a controlled helical sense has been achieved. However, the exact helical structures of most of the already prepared synthetic helical polymers remain unsolved. In this review, the recent progress in the synthesis of helical polymers and their structural determination, including helical pitch and handedness based on X-ray diffraction and spectroscopic measurements, together with high-resolution atomic force microscopy, is described. Polymer Journal (2010) 42, 3-16; doi:10.1038/pj.2009 Keywords: atomic force microscopy; circular dichroism; helical polymer; helical structure; X-ray diffractionThe helix is a unique structure as observed in nature from microscopic to macroscopic levels and is inherently chiral. Inspired by biological helices, such as DNA and proteins, chemists have been challenged to synthesize helical polymers with a controlled helical sense that aims not only to mimic biological helical structures but also to develop chiral materials for the separation of enantiomers and asymmetric catalysis. [1][2][3][4][5][6][7][8][9][10][11][12] The history of synthetic helical polymers with optical activity extends back to the 1960s when Pino and Lorenzi 13 investigated the structural and chiroptical properties of isotactic vinyl polymers prepared by the polymerization of a-olefins bearing optically active substituents. Although helical polyolefins are totally dynamic in nature and consist of short helical segments separated by frequently occurring helical reversals among disordered, random coil conformations, 14 this study was significant in the field of synthetic helical polymers, from which a number of helical polymers have been synthesized.On the basis of the pioneering studies by Nolte et al., 15 Okamoto et al. 16 and Green et al., 17 the existing synthetic helical polymers that exhibit an optical activity solely because of their macromolecular helicity can be classified into two categories with respect to their helix inversion barriers, that is, static and dynamic helical polymers (Figure 1). 9,12 Optically active helical polymers, such as poly(triphenylmethyl methacrylate) (1), 16 poly(t-butyl isocyanide) (2) 15 and polychloral (3), 18 have a sufficiently high helix inversion barrier and belong to the family of static helical polymers. Therefore, these helical polymers with either a right-or left-handed helix can be prepared by the helix-sense-selective polymerization of the corresponding achiral monomers using chiral catalysts or initiators under kinetic control. On the other hand, dynamic helical polymers, such as polyisocyanates (8) 17 and polysilanes (9), 19 possess a very low helix inversion barrier.As a consequence, they consist of interconvertible right-and lefthanded helical segments separated by rarely occurring helical reversals, as demonstrated by Green et al.,6,20,21 so that a preferred-handed helical conformation can be induced in the presence of a small amount of chiral residues at the pendant 6 or ter...

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Majority Rules in the Copolymerization of Mirror Image Isomers

Cited by 371 publications

References 2 publications

Molecular chirality at surfaces

Molecular chirality at surfaces

Self-assembled graphitic nanotubes with one-handed helical arrays of a chiral amphiphilic molecular graphene

Synthesis and structure determination of helical polymers

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