Photo racemization of 2,2′‐dihydroxy‐1,1′‐binaphthyl derivatives

Wang, Qingyu; Pietropaolo, Adriana; Fortino, Mariagrazia; Song, Zhiyi; Bando, Masayoshi; Naga, Naofumi

doi:10.1002/chir.23400

Cited by 8 publications

(4 citation statements)

References 39 publications

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“…This may be reasonable because axial chirality around single bonds connecting aromatic groups has been reported to be significantly affected on photoexcitation. A twisted aromatic–aromatic junction in the ground state can be transformed to a coplanar conformation in excited states (twisted–coplanar transition, TCT). − TCT may not simply cause racemization but may change the conformation of an entire chain for the polymers studied in this work, which have various aromatic–aromatic junctions.…”

Section: Discussionmentioning

confidence: 99%

Optically Active Poly(benzene-1,4-diyl)s with Random and Alternating Copolymer Sequences Composed of Chiral and Achiral, Bulky Monomeric Units: A Systematic Study on Side-Chain Bulkiness Effects on Ground-State and Excited-State Chiroptical Properties and Chiral Recognition Ability

et al. 2022

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Random copolymers comprising chiral and achiral benzene-14,-diyl units were prepared by Ni-mediated copolymerization of optically active 1,4-dibromo-2,5-bis((S)-2-methylbutoxy)benzene with bulky, achiral monomers, i.e., 1,4-dibromo-2,5diphenylbenzene, 1,4-dibromo-2,5-bis(3,5-dimethylphenyl)benzene, 1,4-dibromo-2,5-bis(3,5-bis(trifluoromethyl)phenyl)benzene, and 1,4-dibromo-2,5-bis(3,5-diphenylphenyl)-benzene, and the corresponding alternating copolymers were synthesized by Pd-catalyzed Suzuki−Miyaura cross-coupling of optically active 1,4-bis-(dihydroxyboranyl)-2,5-bis((S)-2-methyl-butoxy)benzene with bulky, achiral monomers. Poly(benzene-1,4-diyl)s with achiral 3,5-disubstituted or unsubstituted phenyl groups and chiral (S)-2-methylbutoxy groups in the side chain were thus obtained. The copolymers showed circular dichroism (CD) spectra whose shapes and intensities largely varied depending on the state of the sample (solution or suspension or film) and the chemical structure. In suspensions and films, both the random and alternating polymers with side-chain 3,5-disubstituted phenyl groups showed intense CD spectra suggestive of a chiral conformation such as preferred-handed helices, while they indicated only moderate CD intensities in solution. Both the random and alternating copolymers with side-chain 3,5disubstituted phenyl groups led to higher anisotropy (g CD ) values than those with side-chain phenyl groups, indicating that sidechain bulkiness plays a role in creating a bias on the population of one enantiomeric structure in the solid state. Among the three 3,5disubstituted phenyl groups, the 3,5-dimethylphenyl group, which is not seemingly the bulkiest one, tended to result in the greatest g CD values. On the other hand, the side-chain 3,5-bis(trifluoromethyl)phenyl group and unsubstituted phenyl groups led to the greatest anisotropy (g lum ) values in circularly polarized light (CPL) emission properties in films for the random and alternating copolymers, indicating that the significance of bulkiness of side-chain groups varies between the ground state and excited states. The alternating copolymer with the side-chain 3,5-bis(trifluoromethyl)phenyl group showed a g lum of +0.012, which arises from the strong electron-withdrawing effects of the −CF 3 group. CPL emission was more significant for the random copolymers than for the alternating copolymers. Some of the polymers exhibited chiral recognition abilities toward trans-stilbene oxide, Troger's base, and flavanone, where resolution performance varied depending on the solvent and polymer structure, and the order of separation factors was not particularly in agreement with the order of g CD values in CD spectra in spite of the fact that CD is often generally used to quantify the chirality of materials.

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Section: Discussionmentioning

confidence: 99%

Optically Active Poly(benzene-1,4-diyl)s with Random and Alternating Copolymer Sequences Composed of Chiral and Achiral, Bulky Monomeric Units: A Systematic Study on Side-Chain Bulkiness Effects on Ground-State and Excited-State Chiroptical Properties and Chiral Recognition Ability

et al. 2022

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“…In this sense, molecular modeling using quantum-chemistry computations as well as enhanced sampling simulations is receiving a lot of interest for the study of photo-physical features and to adequately sample the configurational space of the chiral systems. The development of ab initio methods based on density functional theory (DFT) and its time-dependent extension (TD-DFT) has become fundamental to obtain accurate results for the study of photo-physical properties of medium-large systems [21][22][23][24][25] and can be exploited for accurate theoretical investigations of the chiroptical properties of chiral material models. Specifically, ab initio methods based on DFT and TD-DFT can be used to accurately simulate CD and CPL signals.…”

Section: Introductionmentioning

confidence: 99%

“…Specifically, ab initio methods based on DFT and TD-DFT can be used to accurately simulate CD and CPL signals. It is worth highlighting that, although DFT and its time-dependent extension TD-DFT are among the methods mainly used for the study of the excited states (ESs), [21][22][23][24][25] other valuable level of theories can be also exploited. Indeed, the using of methods such as single excitation configuration interaction methods (CIS) or semi-empirical methods could be adequate alternatives, especially for very large systems allowing to reach a good balance between accuracy and computational cost.…”

Section: Introductionmentioning

confidence: 99%

Simulation workflows to predict the circular dichroism and circularly polarized luminescence of chiral materials

2023

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Chiral materials are attracting considerable interest in various fields in view of their unique properties and optical activity. Indeed, the peculiar features of chiral materials to absorb and emit circularly polarized light enable their use in an extensive range of applications. Motivated by the interest in boosting the development of chiral materials characterized by enhanced chiroptical properties such as circular dichroism (CD) and circular polarized luminescence (CPL), we herein illustrate in this tutorial how theoretical simulations can be used for the predictions and interpretations of chiroptical data and for the identification of chiral geometries. We are focusing on computational frameworks that can be used to investigate the theoretical aspects of chiral materials' photophysical and conformational characteristics. We will then illustrate ab initio methods based on density functional theory (DFT) and its time‐dependent extension (TD‐DFT) to simulate CD and CPL signals, and we will exemplify a variety of enhanced sampling techniques useful for an adequate sampling of the configurational space for chiral systems.

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“…In this study, we applied a modification of our already published balanced detection EC-QCL VCD instrument to follow the changes in the EE of mixtures of R/S-1,1 ′ -bi-2-naphthol, a commonly used motif for chiral catalysis. 24 We demonstrate the ability of QCL-VCD for monitoring a chiral reaction: in a continuous flow cell experiment starting at an enantiopure solution of S-(-)-1,1 ′ -bi-2-naphthol (S-BINOL), aliquots of a solution containing the second enantiomer in the same concentration were added to simulate racemization. The sample solution was continuously circulated between the measurement cell and the mixing vessel, to simulate the environment most probably present in an on-line monitoring scheme.…”

Section: Introductionmentioning

confidence: 99%

Chiral Monitoring Across Both Enantiomeric Excess and Concentration Space: Leveraging Quantum Cascade Lasers for Sensitive Vibrational Circular Dichroism Spectroscopy

Hermann,

Ramer,

Riedlsperger

et al. 2023

Appl Spectrosc

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Recently, high-throughput quantum cascade laser-based vibrational circular dichroism (QCL-VCD) technology has reduced the measurement time for high-quality vibrational circular dichroism spectra from hours to a few minutes. This study evaluates QCL-VCD for chiral monitoring using flow-through measurement of a changing sample in a circulating loop. A balanced detection QCL-VCD system was applied to the enantiomeric pair R/S-1,1′-bi-2-naphthol in solution. Different mixtures of the two components were used to simulate a racemization process, collecting spectral data at a time resolution of 6 min, and over three concentration levels. The goal of this experimental setup was to evaluate QCL-VCD in terms of both molar and enantiomeric excess (EE) sensitivity at a time resolution relevant to chiral monitoring in chemical processes. Subsequent chemometric evaluation by partial least squares regression revealed a cross-validated prediction accuracy of 2.8% EE with a robust prediction also for the test data set (error = 3.5% EE). In addition, the data set was also treated with the least absolute shrinkage and selection operator (LASSO), which also achieved a robust prediction. Due to the operating principle of LASSO, the obtained coefficients constituted a few discrete spectral frequencies, which represent the most variance. This information can be used in the future for dedicated QCL-based instrument design, gaining a higher time resolution without sacrificing predictive capabilities.

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Photo racemization of 2,2′‐dihydroxy‐1,1′‐binaphthyl derivatives

Cited by 8 publications

References 39 publications

Optically Active Poly(benzene-1,4-diyl)s with Random and Alternating Copolymer Sequences Composed of Chiral and Achiral, Bulky Monomeric Units: A Systematic Study on Side-Chain Bulkiness Effects on Ground-State and Excited-State Chiroptical Properties and Chiral Recognition Ability

Optically Active Poly(benzene-1,4-diyl)s with Random and Alternating Copolymer Sequences Composed of Chiral and Achiral, Bulky Monomeric Units: A Systematic Study on Side-Chain Bulkiness Effects on Ground-State and Excited-State Chiroptical Properties and Chiral Recognition Ability

Simulation workflows to predict the circular dichroism and circularly polarized luminescence of chiral materials

Chiral Monitoring Across Both Enantiomeric Excess and Concentration Space: Leveraging Quantum Cascade Lasers for Sensitive Vibrational Circular Dichroism Spectroscopy

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