Optical activity in the biaryl series

Mason, S. F.; Seal, Richard H.; Roberts, David

doi:10.1016/s0040-4020(01)90689-1

Cited by 227 publications

(169 citation statements)

References 37 publications

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“…That alterations in this dihedral angle can impact the CD and optical rotation behaviors of smaller chiral binaphthylene derivatives has been widely demonstrated in a number of earlier reports. [23][24][25] An inspection of the twin plots shown in Figure 3 clearly reveals that the measured rotation magnitudes for polymers 1(R) through 6 dissolved in DMAC are linearly related to the loading of the (R)-binaphthylene groups positioned along the polymer backbone. This trend in the chiroptical data holds both before and after near-UV light exposure.…”

Section: Stimuli-responsive Chiroptical Behaviormentioning

confidence: 95%

Stimuli-Responsive Polymers VI. Azobenzene Modified Copolyaramides with Chiral Helical Geometries: Influence of Rigid, Helix-Disrupting Segments on Physiochemical and Chiroptical Behavior

Jaycox

2002

Polym J

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ABSTRACT:Polymers comprised of alternating trans-4,4 -azobenzene and helix directing (R)-2,2 -binaphthylene backbone linkages adopt single handed helical conformations in solution that are reversibly distorted by light and heat regulated trans ↔ cis isomerization processes. The replacement of (R)-binaphthylene backbone groups with helixdisrupting 4,4 -diphenylfluorene segments affords permanent changes in some of the properties exhibited by this family of optically active materials. Polymer solubilities in organic solvents like THF and acetone are significantly diminished while thermal stabilities and photophysical behavior remain largely unchanged. Optical rotation magnitudes measured at the sodium D-line drop in a linear manner with the loss of the atropisomeric binaphthylene linkages. However, all of the polymer variants exhibit stimuli-responsive chiroptical behavior when evaluated in DMAC or THF solution environments. Specific rotation magnitudes are reversibly diminished by the near-UV light induced trans → cis isomerization reaction. Optical rotatory power is restored by reverse cis → trans isomerization processes triggered by heat or by visible light illumination. That stimuli-responsive chiroptical properties are exhibited by all polymer variants regardless of their monomer compositions indicates that global helical order along the polymer backbone is not necessarily required for this effect. Rather, isomerization induced perturbations to the local dihedral angles residing in the atropisomeric binaphthylene main chain segments likely serve as the genesis for photo-and thermo-regulated behavior in these materials.KEY WORDS Stimuli-Responsive Chiroptical Behavior / trans-cis Azobenzene Isomerization / Helical Polymers / Circular Dichroism / Optical Rotation / Exciton Coupling / Cardo Polymers / Macromolecules endowed with single-handed helical geometries can be prepared by a variety of synthetic methods. Monomers based on chiral 1,1 -binaphthylenes, 1,1 -biphenylenes and other axially dissymmetric ring systems provide convenient access to condensation polymers with chiral helical motifs. The polycondensation of (R)-(+)-1,1 -binaphthyl-2,2 -diamine with terephthaloyl chloride was first reported by Schulz and Jung over thirty years ago. 1 The resulting polyaramide exhibited significant optical rotatory power that was attributed to the presence of a single helical screw sense along the polymer's conformationally restricted backbone. In the decades that have followed, a variety of other optically active macromolecules have been assembled from atropisomeric, helix-directing monomers using this same generalized approach. 2 Earlier, this laboratory reported the preparation of a number of helical trans-azobenzene modified polyaramides from both (R)-and (S )-1,1 -binaphthyl-2,2 -diamine. 3, 4 Some of these materials were specifically designed to undergo reversible helix order ↔ disorder transitions in response to multiple trans ↔ cis azobenzene isomerization reactions triggered within the polymer's main chain. [5]...

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Section: Stimuli-responsive Chiroptical Behaviormentioning

confidence: 95%

Stimuli-Responsive Polymers VI. Azobenzene Modified Copolyaramides with Chiral Helical Geometries: Influence of Rigid, Helix-Disrupting Segments on Physiochemical and Chiroptical Behavior

Jaycox

2002

Polym J

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“…As the CD behaviour of a biaryl compound does not only depend on its formal absolute configuration, but also strongly on the conformation at the biaryl axis [16], several structures with different biaryl dihedral angles have to be taken into account. These were generated by varying the biaryl dihedral angle 9-5-5'-9' of the energetic minimum structures (here for 2a and 2b) in steps of several degrees, then fixing this angle and again optimizing all other internal coordinates.…”

Section: Methodsmentioning

confidence: 99%

The Absolute Configuration of Isoancistrocladine and 'Isohamatine' by Quantumchemical CD-Calculations

Fleischhauer

Koslowski

Repges

et al. 1998

Zeitschrift Für Naturforschung A

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The absolute configuration of the naphthylisoquinolines isoancistrocladine and isohamatine at the biaryl axis was determined by comparing the measured and the calculated CD spectra.In order to calculate these spectra we used the CNDO/S method in combination with a Boltzmann weighting of conformers with different dihedral angles at the biaryl axis. The Boltzmann factors were obtained with the AM 1 method.

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“…The CD spectra of 1,1'-biphenyls contain similar changes in sign to low energy of the main bands, although the reasons for this have not been examined in any depth. [23] The most plausible explanation for this is that the flexibility of the binaphthyl substituents results in a wide range of different conformations in solution. As revealed by single crystal analysis, the naphthalene ring moieties exhibit obvious deviation from planarity due to the wide range of different values for α (α＝65.8°± 6.8°) and θ (θ＝59.8°±4.1°), also in combination with the flexibility of the binaphthyl substituents.…”

Section: Electronic Absorption Magnetic Circular Dichroism and Circmentioning

confidence: 99%

Chiral Phthalocyanine with Unambiguous Absolute Molecular Structures for Both Enantiomers

Wang¹,

Wang²,

Mack³

et al. 2012

Acta Chim. Sinica

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Optical activity in the biaryl series

Cited by 227 publications

References 37 publications

Stimuli-Responsive Polymers VI. Azobenzene Modified Copolyaramides with Chiral Helical Geometries: Influence of Rigid, Helix-Disrupting Segments on Physiochemical and Chiroptical Behavior

Stimuli-Responsive Polymers VI. Azobenzene Modified Copolyaramides with Chiral Helical Geometries: Influence of Rigid, Helix-Disrupting Segments on Physiochemical and Chiroptical Behavior

The Absolute Configuration of Isoancistrocladine and 'Isohamatine' by Quantumchemical CD-Calculations

Chiral Phthalocyanine with Unambiguous Absolute Molecular Structures for Both Enantiomers

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