Vibrational circular dichroism and single crystal X-Ray diffraction analyses of [Ir(bzq)<sub>2</sub>(phen)]<sup>+</sup> (bzq = benzo[h]quinoline; phen = 1,10-phenanthroline): absolute configuration and role of CH–π interaction in molecular packing

Takimoto, Kazuyoshi; Watanabe, Yutaka; Mori, Shigeki; Sato, Hisako

doi:10.1039/c7dt00606c

Cited by 19 publications

(6 citation statements)

References 53 publications

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“…To assign the Δ, Λ isomers unambiguously, vibrational circular dichroism (VCD) spectra were further recorded and compared with those of Ru-acac . VCD spectral analysis has been effective in determining chirality, including Δ, Λ isomerism. − The VCD spectra of Ru-Br 1 trop , Ru-Br 2 trop , and Ru-Br 3 trop (Figures S17–S20) are consistent with those of Δ, Λ- Ru-acac , , confirming the assignments of Δ, Λ chirality based on the ECD spectra. Finally, we verified the absolute configuration of the strongly retained fraction of Ru-Br 1 trop (Λ isomer) by single-crystal X-ray diffraction study.…”

Section: Resultssupporting

confidence: 56%

Comprehensive Understanding of Host- and Guest-Dependent Helix Inversion in Chiral Nematic Liquid Crystals: Experimental and Molecular Dynamics Simulation Study

Yoshida¹,

Tamura²,

Hoshino³

et al. 2018

J. Phys. Chem. B

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Nematic liquid crystals (LCs) are known to transform into chiral nematic LCs with helical structures upon doping with enantiomeric compounds (called chiral dopants or guests). Here, we investigated the mechanism of host LC- and guest-dependent helix inversion by using octahedral metal complexes as guests. The helical twisting powers (HTPs/μm–1) of eight metal complexes with Δ, Λ chirality were examined in five nematic LC hosts. For example, Δ-[Ru(acac)2(trop)] (Ru-trop, Hacac = 2,4-pentanedione, Htrop = tropolone) induces a left-handed (M) helix upon doping with N-(4-methoxybenzylidene)-4-butylaniline (MBBA), whereas it induces an opposite right-handed (P) helix in 4-cyano-4′-pentylbiphenyl (5CB). The monobrominated complex of Ru-trop, Δ-[Ru(acac)2(Brtrop)] (Ru-Br 1 trop, HBr1trop = 5-bromotropolone), induces P helices in both MBBA and 5CB, whereas the dibrominated complex, Δ-[Ru(acac)2(Br2trop)] (Ru-Br 2 trop, HBr2trop = 3,7-dibromotroplone) induces M helices in both the media. The molecular dynamics simulation performed in parallel confirmed the drastic effect of the bromo groups on the microscopic ordering direction of guests in nematics. Further, HTPs of all Δ isomers of metal complexes investigated were found to shift in the positive direction as the dielectric constant anisotropy (Δε) of the host LCs increases (and vice versa for Λ isomers). These experimental and calculated results highlight the interplay of steric (excluded volume effect) and electrostatic (dipole–dielectric body) interactions between the host LCs and guest metal complexes.

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Section: Resultssupporting

confidence: 56%

Comprehensive Understanding of Host- and Guest-Dependent Helix Inversion in Chiral Nematic Liquid Crystals: Experimental and Molecular Dynamics Simulation Study

Yoshida¹,

Tamura²,

Hoshino³

et al. 2018

J. Phys. Chem. B

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“…[19,86] Nevertheless, there are a number of successful theoretical studies based on molecular clusters being reported. [19,[87][88][89][90][91][92][93][94][95][96][97][98][99][100] Especially for the simpler achiral space groups this approach seems feasible. P2 1 , for instance, contains only two molecules per unit cell, which is straightforwardly translated into a cluster by adding a few more molecules to mitigate the boundary effects.…”

Section: Methodsmentioning

confidence: 99%

“…It is also the finite size effects, the distortion of cluster geometry upon structure optimisation and the introduction of unsaturated non‐covalent interactions that result in biased absorption frequencies and wrong VCD signs [19, 86] . Nevertheless, there are a number of successful theoretical studies based on molecular clusters being reported [19, 87–100] . Especially for the simpler achiral space groups this approach seems feasible.…”

Section: Vibrational Circular Dichroism (Vcd) Theorymentioning

confidence: 99%

Vibrational Circular Dichroism Spectroscopy of Chiral Molecular Crystals: Insights from Theory

Jähnigen

2023

Angew Chem Int Ed

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Chirality is a curious phenomenon that appears in various forms. While the concept of molecular (RS‐)chirality is ubiquitous in chemistry, there are also more intricate forms of structural chirality. One of them is the enantiomorphism of crystals, especially molecular crystals, that describes the lack of mirror symmetry in the unit cell. Its relation to molecular chirality is not obvious, but still an open question, which can be addressed with chiroptical tools. Vibrational circular dichroism (VCD) denotes chiral infrared (IR) spectroscopy that is susceptible to both, the molecular as well as the intermolecular space by means of vibrational transitions. When carried out in the solid state, VCD delivers a very rich set of non‐local contributions that are determined by crystal packing and collective motion. Since its discovery in the 1970s, VCD has become the method of choice for the determination of absolute configurations, but its applicability reaches beyond towards the study of different crystal forms and polymorphism. This brief review summarises the theoretical concepts of crystal chirality and how computations of solid‐state VCD can shed light into the intimate connection of chiral structure and vibrational optical activity.

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“…Using tridentate ligands, Soloshonok et al prepared binuclear nickel(II) complexes like 95 with a ridge-tile-like chiral topology and characterized the bended structure using VCD . Studies on luminescent transition metal complexes such as 96 − or 97 benefited from the additional structural insights obtained from VCD spectroscopy as well. Chiral rhenium complexes such as 98 , have been of interest in studies on parity violations.…”

Section: Demonstrating the Diversity Of Ac Determinations Carried Out...mentioning

confidence: 99%

Absolute Configurations of Synthetic Molecular Scaffolds from Vibrational CD Spectroscopy

2019

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Vibrational circular dichroism (VCD) spectroscopy is one of the most powerful techniques for the determination of absolute configurations (AC), as it does not require any specific UV/vis chromophores, no chemical derivatization, and no growth of suitable crystals. In the past decade, it has become increasingly recognized by chemists from various fields of synthetic chemistry such as total synthesis and drug discovery as well as from developers of asymmetric catalysts. This perspective article gives an overview about the most important experimental aspects of a VCD-based AC determination and explains the theoretical analysis. The comparison of experimental and computational spectra that leads to the final conclusion about the AC of the target molecules is described. In addition, the review summarizes unique VCD studies carried out in the period 2008−2018 that focus on the determination of unknown ACs of new compounds, which were obtained in its enantiopure form either through direct asymmetric synthesis or chiral chromatography.

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Vibrational circular dichroism and single crystal X-Ray diffraction analyses of [Ir(bzq)₂(phen)]⁺ (bzq = benzo[h]quinoline; phen = 1,10-phenanthroline): absolute configuration and role of CH–π interaction in molecular packing

Cited by 19 publications

References 53 publications

Comprehensive Understanding of Host- and Guest-Dependent Helix Inversion in Chiral Nematic Liquid Crystals: Experimental and Molecular Dynamics Simulation Study

Comprehensive Understanding of Host- and Guest-Dependent Helix Inversion in Chiral Nematic Liquid Crystals: Experimental and Molecular Dynamics Simulation Study

Vibrational Circular Dichroism Spectroscopy of Chiral Molecular Crystals: Insights from Theory

Absolute Configurations of Synthetic Molecular Scaffolds from Vibrational CD Spectroscopy

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Vibrational circular dichroism and single crystal X-Ray diffraction analyses of [Ir(bzq)2(phen)]+ (bzq = benzo[h]quinoline; phen = 1,10-phenanthroline): absolute configuration and role of CH–π interaction in molecular packing

Cited by 19 publications

References 53 publications

Comprehensive Understanding of Host- and Guest-Dependent Helix Inversion in Chiral Nematic Liquid Crystals: Experimental and Molecular Dynamics Simulation Study

Comprehensive Understanding of Host- and Guest-Dependent Helix Inversion in Chiral Nematic Liquid Crystals: Experimental and Molecular Dynamics Simulation Study

Vibrational Circular Dichroism Spectroscopy of Chiral Molecular Crystals: Insights from Theory

Absolute Configurations of Synthetic Molecular Scaffolds from Vibrational CD Spectroscopy

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Vibrational circular dichroism and single crystal X-Ray diffraction analyses of [Ir(bzq)₂(phen)]⁺ (bzq = benzo[h]quinoline; phen = 1,10-phenanthroline): absolute configuration and role of CH–π interaction in molecular packing