Carbo[<i>n</i>]helicenes Restricted to Enantiomerize: An Insight into the Design Process of Configurationally Stable Functional Chiral PAHs

Ravat, Prince

doi:10.1002/chem.202004488

Cited by 91 publications

(125 citation statements)

References 67 publications

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“… [43] The coalescence temperature T c for the observed process is 303 K and the rotational barrier Δ G ≠ of 64.7 kJ mol −1 is comparable to values obtained for the rotation of different imide substituents in PBIs around the terminal C−N single bond, indicating the feasibility of this rotation at room temperature. [44] DFT calculations (Figure S4) provide a reasonable approximation for the rotational barrier and insights into the distortions required for the rotation of the aryl groups and the energetically more demanding enantiomerization that resembles the related processes in carbohelicenes [45] and in tetramethoxy perylene bisimides. [46] …”

Section: Resultsmentioning

confidence: 99%

Chiral Perylene Bisimide Dyes by Interlocked Arene Substituents in the Bay Area

Renner

Mahlmeister²,

Anhalt³

et al. 2021

Chemistry A European J

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A series of perylene bisimide (PBI) dyes bearing various aryl substituents in 1,6,7,12 bay positions has been synthesized by Suzuki cross‐coupling reaction. These molecules exhibit an exceptionally large and conformationally fixed twist angle of the PBI π‐core due to the high steric congestion imparted by the aryl substituents in bay positions. Single crystal X‐ray analyses of phenyl‐, naphthyl‐ and pyrenyl‐functionalized PBIs reveal interlocked π‐π‐stacking motifs, leading to conformational chirality and the possibility for the isolation of enantiopure atropoisomers by semipreparative HPLC. The interlocked arrangement endows these molecules with substantial racemization barriers of about 120 kJ mol−1 for the tetraphenyl‐ and tetra‐2‐naphthyl‐substituted derivatives, which is among the highest racemization barriers for axially chiral PBIs. Variable temperature NMR studies reveal the presence of a multitude of up to fourteen conformational isomers in solution that are interconverted via smaller activation barriers of about 65 kJ mol−1. The redox and optical properties of these core‐twisted PBIs have been characterized by cyclic voltammetry, UV/Vis/NIR and fluorescence spectroscopy and their respective atropo‐enantiomers were further characterized by circular dichroism (CD) and circular polarized luminescence (CPL) spectroscopy.

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Section: Resultsmentioning

confidence: 99%

Chiral Perylene Bisimide Dyes by Interlocked Arene Substituents in the Bay Area

Renner

Mahlmeister²,

Anhalt³

et al. 2021

Chemistry A European J

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“…There are cases where the enantiomerization is undesirable; for example, many drugs are related to chirality, and frequently, only one of the enantiomers shows the desired effect, while the other shows undesirable effects. Chiral molecules with a high charge-carrier mobility and fluorescence quantum yield need high-energy barriers for enantiomerization [ 147 ].…”

Section: Resultsmentioning

confidence: 99%

Theoretical Prediction of Structures, Vibrational Circular Dichroism, and Infrared Spectra of Chiral Be4B8 Cluster at Different Temperatures

et al. 2021

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Lowest-energy structures, the distribution of isomers, and their molecular properties depend significantly on geometry and temperature. Total energy computations using DFT methodology are typically carried out at a temperature of zero K; thereby, entropic contributions to the total energy are neglected, even though functional materials work at finite temperatures. In the present study, the probability of the occurrence of one particular Be4B8 isomer at temperature T is estimated by employing Gibbs free energy computed within the framework of quantum statistical mechanics and nanothermodynamics. To identify a list of all possible low-energy chiral and achiral structures, an exhaustive and efficient exploration of the potential/free energy surfaces is carried out using a multi-level multistep global genetic algorithm search coupled with DFT. In addition, we discuss the energetic ordering of structures computed at the DFT level against single-point energy calculations at the CCSD(T) level of theory. The total VCD/IR spectra as a function of temperature are computed using each isomer’s probability of occurrence in a Boltzmann-weighted superposition of each isomer’s spectrum. Additionally, we present chemical bonding analysis using the adaptive natural density partitioning method in the chiral putative global minimum. The transition state structures and the enantiomer–enantiomer and enantiomer–achiral activation energies as a function of temperature evidence that a change from an endergonic to an exergonic type of reaction occurs at a temperature of 739 K.

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“…Optically‐active ( P 5 , M 4 )‐ and ( M 5 , P 4 )‐TH‐ 2 b with optical purities of >98% ee were obtained by chiral HPLC under modified chromatographic conditions affording better resolution of ( P 5 , P 4Ph , M 4 )‐ and ( M 5 , M 4Ph , P 4 )‐isomers (Figure S17; for racemization kinetics and thermodynamics for ( P 5 , M 4 )‐TH‐ 2 b , see Figure S18). QH‐ 2 b could not be resolved by chiral HPLC under any of the conditions investigated, most likely because of four [4]helicene subunits with a low helicity inversion barrier [14b,16] …”

Section: Resultsmentioning

confidence: 99%

One‐Step Simultaneous Synthesis of Circularly Polarized Luminescent Multiple Helicenes Using a Chrysene Framework

Ikai

Yamakawa

Suzuki

et al. 2021

Chemistry An Asian Journal

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A series of multiple helicenes was simultaneously synthesized in one step by intramolecular cyclization of a single chrysene derivative containing two 2-[(4-alkoxyphenyl)ethynyl]phenyl units accompanied by rearrangements of the aryl pendants. The electrophile-induced double cyclization with or without aryl migrations proceeded efficiently under acidic conditions to afford annulative p-extension of the chrysene units and produced quadruple (QH-2), triple (TH-2), and double (DH-2) helicenes containing [4]-and/or [5]helicene frameworks with dynamic and/or static helicene chirality in one step. Three multiple helicenes' structures were determined by X-ray crystallography and/or density functional theory calculations. The multiple TH-2 and DH-2 helicenes were separated into enantiomers because of the stable one and two [5]helicene moieties, respectively, and showed intense circular dichroism and circularly polarized luminescence. Although QH-2, which comprises four [4]helicene subunits, was not resolved into enantiomers, the TH-2 enantiomers were further separated into a pair of diastereomers at low temperature resulting from their substituted [4]helicene chirality. File list (2) download file view on ChemRxiv Ikai_ChemRxiv.pdf (1.17 MiB) download file view on ChemRxiv IkaiSI_ChemRxiv.pdf (23.71 MiB)

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Carbo[n]helicenes Restricted to Enantiomerize: An Insight into the Design Process of Configurationally Stable Functional Chiral PAHs

Cited by 91 publications

References 67 publications

Chiral Perylene Bisimide Dyes by Interlocked Arene Substituents in the Bay Area

Chiral Perylene Bisimide Dyes by Interlocked Arene Substituents in the Bay Area

Theoretical Prediction of Structures, Vibrational Circular Dichroism, and Infrared Spectra of Chiral Be4B8 Cluster at Different Temperatures

One‐Step Simultaneous Synthesis of Circularly Polarized Luminescent Multiple Helicenes Using a Chrysene Framework

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