Rotamerism in 2,2′-binaphthyl. A study based on fluorescence analysis and CS-INDO/CI calculations

Baraldi, Ivan; Bruni, Maria C.; Caselli, Monica; Ponterini, Glauco

doi:10.1039/f29898500065

Cited by 26 publications

(30 citation statements)

References 2 publications

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“…Chirality has become one of the most important and complex topics of liquid crystal research today [ 1,2]. The existence of many mesophases is due to chirality; examples include cholesteric or twisted nematic mesophases, blue phases [3,4] and twist grain boundary (TGB) phases [S, 61.…”

Section: Introductionmentioning

confidence: 99%

New 6,6′-disubstituted-binaphthol derivatives as chiral dopants: Synthesis and temperature dependence of molecular conformations

et al. 1996

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A number of new chiral binaphthol (BN) derivatives with different substituents R,R in the 6,6'-positions in open (BN-diethylethers) and bridged forms (BN-acetals) have been synthesized. The syntheses of the chiral 6,6-disubstituted-2,2'-diethoxy-l,l'-binaphthyls (R,R = -CH=CHCHO, -CH =CH-( p-BrPh), -CH=CH-(p-CHOPh)) and the chiral 9,14-disubstituted-dinaphtho[2,1-d : 1',2'-f][ 1,3] dioxepins with R,R' = -CH=CH-( p-BrPh), -CH=CH-( p-CHOPh) are reported for the first time. The possible liquid crystalline properties and molar twisting powers (pM) in three different nematic liquid crystals (LCs) of the BN derivatives were investigated. Derivatives with spatially extended substituents in the 6,6'-positions (e.g. styryl or vinyl) show unusually high molar twisting power (up to 1245 pm-').A direct correlation between the magnitude of pM and the length of the substituents was found. Bridged forms, in which the dihedral angle 0 between the naphthyl moieties is x54, show higher twisting power than the corresponding open forms, where 0 is allowed to vary around 90" resulting in an equilibrium between transoid and cisoid forms. From the different temperature dependencies of PM of the open and bridged BNs, a molecular model was developed relating the molecular conformation and twisting power. Although no mesophase was found in any of the compounds synthesized, they can be considered as important precursors for the synthesis of potential chiral BN-containing LCs.

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Section: Introductionmentioning

confidence: 99%

New 6,6′-disubstituted-binaphthol derivatives as chiral dopants: Synthesis and temperature dependence of molecular conformations

et al. 1996

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“…Besides CD, fluorescence spectroscopy can provide valuable information about the nature of the excited state of biaryl compounds. − (S a )-binol, (R a )-PL1, and (R a )-PL2 in Cx (Figure c) exhibit a broad fluorescence spectrum with a Stokes shift higher than 2700 cm –1 . Such a behavior, which was also reported for the achiral 1,1′-binaphthyl, has been attributed to the significant change of θ upon excitation .…”

mentioning

confidence: 99%

Unveiling Excited-State Chirality of Binaphthols by Femtosecond Circular Dichroism and Quantum Chemical Calculations

Schmid

Martínez‐Fernández

Markovitsi

et al. 2019

J. Phys. Chem. Lett.

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Time-resolved circular dichroism (TR-CD) is a powerful tool for probing conformational dynamics of biomolecules over large time scales that are crucial for establishing their structure−function relationship. However, such experiments, notably in the femtosecond regime, remain challenging due to their extremely weak signals, prone to polarization artifacts. By using binol and two bridged derivatives (PL1 and PL2) as chiral prototypes, we present here the first comprehensive study of this type in the middle UV, combining femtosecond TR-CD and quantum mechanical calculations (TD-DFT). We show that excitation of the three compounds induces large variations of their transient CD signals, in sharp contrast to those of their achiral transient absorption. We demonstrate that these variations arise from both the alteration of the electronic distribution and the dihedral angle in the excited state. These results highlight the great sensitivity of TR-CD detection to signals hardly accessible to achiral transient absorption.

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“…57 Compared with 1,1 0 -BN, past research on 2,2 0 -BN is even rarer. 28,45 As for ab initio and DFT calculations, Zhang et al have used Hartree-Fock and B3LYP for the equilibrium geometries of the ground states, and configuration interaction with singles (CIS) and time-dependent DFT for those of the excited states of 1,1 0 -BN and 2,2 0 -BN. 46 However, due to the large size of BNs, Zhang et al have employed only a relatively small basis set as 3-21G.…”

Section: A Ab Initio and Dft Calculations Of The Torsional Potential ...mentioning

confidence: 99%

“…Due to the different linkage positions, the steric hindrance for the torsion is much higher in 1,1 0 -BN than in 2,2 0 -BN. 44,45 We attempted to see how the difference in degree of steric hindrance affected the IVR rate by taking dispersed fluorescence spectra at different excess energies. We also calculated the torsional potential energy curve for both molecules in the ground state by ab initio and density functional theory (DFT) methods with medium-sized basis sets to extend the previous work done with small basis sets 46 and to compare the relative magnitudes of their steric hindrances.…”

Section: Introductionmentioning

confidence: 99%

Effect of ring torsion on intramolecular vibrational redistribution dynamics of 1,1′-binaphthyl and 2,2′-binaphthyl

Lee

Park²,

Yoon

et al. 2012

Phys. Chem. Chem. Phys.

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The role of ring torsion in the enhancement of intramolecular vibrational energy redistribution (IVR) in aromatic molecules was investigated by conducting excitation and dispersed fluorescence spectroscopy of 1,1'-binaphthyl (1,1'-BN) and 2,2'-BN. The dispersed fluorescence spectra of 1,1'-BN in the origin region of S(1)-S(0) were well resolved, which presented 25-27 cm(-1) gaps of torsional mode in the ground state. The overall profile of the dispersed spectra of 1,1'-BN is similar to that of naphthalene. In contrast, the spectra of 2,2'-BN were not resolved due to the multitude of the active torsional modes. In both cases, dissipative IVR was observed to take place with a relatively small excess vibrational energy: 237.5 cm(-1) for 1,1'-BN and 658 cm(-1) for 2,2'-BN, which clearly shows that ring torsion efficiently enhances the IVR rate. Ab initio and density functional theory calculations with medium-sized basis sets showed that the torsional potential of 1,1'-BN has a very flat minimum over the range of torsional angles from ca. 60° to 120°, whereas that of 2,2'-BN showed two well-defined potential minima at ca. 40° and 140°, in resemblance to the case of biphenyl. In this work, we propose that aromatic molecules be classified into "strong" and "weak" torsional hindrance cases: molecules with strong hindrance case show shorter torsional progressions and more effective IVR dynamics than do those with weak hindrance.

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Rotamerism in 2,2′-binaphthyl. A study based on fluorescence analysis and CS-INDO/CI calculations

Cited by 26 publications

References 2 publications

New 6,6′-disubstituted-binaphthol derivatives as chiral dopants: Synthesis and temperature dependence of molecular conformations

New 6,6′-disubstituted-binaphthol derivatives as chiral dopants: Synthesis and temperature dependence of molecular conformations

Unveiling Excited-State Chirality of Binaphthols by Femtosecond Circular Dichroism and Quantum Chemical Calculations

Effect of ring torsion on intramolecular vibrational redistribution dynamics of 1,1′-binaphthyl and 2,2′-binaphthyl

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