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Ožegović A, Knežević A, Novak J, Šegota S, Davidson P, Lesac A. The Interplay of Spacer Chirality and Parity in Mesogenic Dimers. Chemphyschem 2024; 25:e202400065. [PMID: 38406969 DOI: 10.1002/cphc.202400065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 02/23/2024] [Accepted: 02/23/2024] [Indexed: 02/27/2024]
Abstract
Introducing chirality into soft materials, including liquid crystals (LCs), profoundly impacts their self-organization and physical properties. In this study, we synthesized a novel series of LC dimers with a chiral center as part of their flexible spacer. The dimers were prepared in racemic and enantiomerically pure forms. Their spacer length and parity were varied to investigate the effect of spacer chirality and parity on mesomorphic behavior and on chiral induction in the nematic phase of achiral mesogens. Our results show that the even-membered chiral dimers only have chiral nematic phases. In contrast, the odd-membered dimers display rich mesomorphism, including the intriguing blue phase (BP) and chiral form of the twist-bend nematic phase (N*TB). The observed significant difference in the 3D surface morphology between the racemic and chiral forms of the N*TB phase suggests that the chiral moiety in the spacer promotes a chiral hierarchy. Furthermore, the chiral dimers show a prominent odd-even effect in the helical twisting power in nematic hosts. These findings highlight the importance of the position of the chiral group within the dimeric molecule and provide new insights into how intrinsic chirality in the spacer affects the overall structural chirality.
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Affiliation(s)
| | | | - Jurica Novak
- University of Rijeka, Center for Artificial Intelligence and Cyber Security, Radmile Matejčić 2, 51000, Rijeka, Croatia
| | - Suzana Šegota
- Ruđer Bošković Institute, Bijenička 54, 10000, Zagreb, Croatia
| | - Patrick Davidson
- Laboratoire de Physique des Solides, Université Paris-Saclay, CNRS, 91405, Orsay, France
| | - Andreja Lesac
- Ruđer Bošković Institute, Bijenička 54, 10000, Zagreb, Croatia
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Walker R, Pociecha D, Salamonczyk M, Storey JMD, Gorecka E, Imrie CT. Intrinsically Chiral Twist-Bend Nematogens: Interplay of Molecular and Structural Chirality in the N TB Phase. Chemphyschem 2023; 24:e202200807. [PMID: 36422888 DOI: 10.1002/cphc.202200807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 11/24/2022] [Accepted: 11/24/2022] [Indexed: 11/27/2022]
Abstract
Non-symmetric lactate-based chiral liquid crystal dimers containing an odd-membered spacer are shown to exhibit a chiral twist-bend nematic phase which is stable on cooling to room temperature. A comparison of racemic and optically pure materials reveals that the pitch length in the N*TB phase is not influenced by molecular chirality, whereas the nematic-twist-bend nematic transition temperature is increased.
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Affiliation(s)
- Rebecca Walker
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Meston Building, AB24 3UE, Aberdeen, UK
| | - Damian Pociecha
- Faculty of Chemistry, University of Warsaw, ul. Zwirki i Wigury 101, 02-089, Warsaw, Poland
| | - Miroslaw Salamonczyk
- Faculty of Chemistry, University of Warsaw, ul. Zwirki i Wigury 101, 02-089, Warsaw, Poland
| | - John M D Storey
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Meston Building, AB24 3UE, Aberdeen, UK
| | - Ewa Gorecka
- Faculty of Chemistry, University of Warsaw, ul. Zwirki i Wigury 101, 02-089, Warsaw, Poland
| | - Corrie T Imrie
- Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Meston Building, AB24 3UE, Aberdeen, UK
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Dokli I, Ožegović A, Šimanović A, Hromin M, Knežević A, Višnjevac A, Lesac A. Enantioselective Synthesis of 3-Aryl-3-hydroxypropanoic Esters as Subunits for Chiral Liquid Crystals. J Org Chem 2022; 87:14045-14057. [PMID: 36221167 DOI: 10.1021/acs.joc.2c01662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Chiral liquid crystals (LCs) with their unique optical and mechanical properties are perspective functional soft materials for fundamental science and advanced technological applications. Herein, we introduce the chiral 3-aryl-3-hydroxypropanoic ester moiety as a versatile building block for the preparation of LC compounds. Three chiral subunits differing in the aromatic part were obtained through asymmetric transfer hydrogenation using Ru(II) complexes with ee from 98% to >99%. Chiral LC compounds of diverse topologies were further prepared without deterioration of the ee during the synthesis. The mesomorphic behavior of rod-shaped, bent-shaped flexible dimeric, and polycatenar LCs is consistent with their topology─chiral nematic and smectic phases were identified as well as the rarely observed twist grain boundary A and blue phases. The utilization of synthetic chiral building blocks offers the possibility of fine tuning the intermolecular interactions by subtle changes in the molecular structure as well as the preparation of the corresponding racemic forms. This paves the way for the study of self-organization and the structure-property relationship in chiral soft materials.
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Affiliation(s)
- Irena Dokli
- Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia
| | | | | | - Matija Hromin
- Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia
| | | | | | - Andreja Lesac
- Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia
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Arakawa Y, Ishida Y, Komatsu K, Arai Y, Tsuji H. Thioether-linked benzylideneaniline-based twist-bend nematic liquid crystal dimers: Insights into spacer lengths, mesogenic arm structures, and linkage types. Tetrahedron 2021. [DOI: 10.1016/j.tet.2021.132351] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Pocock EE, Mandle RJ, Goodby JW. Experimental and Computational Study of a Liquid Crystalline Dimesogen Exhibiting Nematic, Twist-Bend Nematic, Intercalated Smectic, and Soft Crystalline Mesophases. Molecules 2021; 26:532. [PMID: 33498518 PMCID: PMC7864162 DOI: 10.3390/molecules26030532] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 01/18/2021] [Accepted: 01/19/2021] [Indexed: 11/16/2022] Open
Abstract
Liquid crystalline dimers and dimesogens have attracted significant attention due to their tendency to exhibit twist-bend modulated nematic (NTB) phases. While the features that give rise to NTB phase formation are now somewhat understood, a comparable structure-property relationship governing the formation of layered (smectic) phases from the NTB phase is absent. In this present work, we find that by selecting mesogenic units with differing polarities and aspect ratios and selecting an appropriately bent central spacer we obtain a material that exhibits both NTB and intercalated smectic phases. The higher temperature smectic phase is assigned as SmCA based on its optical textures and X-ray scattering patterns. A detailed study of the lower temperature smectic ''X'' phase by optical microscopy and SAXS/WAXS demonstrates this phase to be smectic, with an in-plane orthorhombic or monoclinic packing and long (>100 nm) out of plane correlation lengths. This phase, which has been observed in a handful of materials to date, is a soft-crystal phase with an anticlinic layer organisation. We suggest that mismatching the polarities, conjugation and aspect ratios of mesogenic units is a useful method for generating smectic forming dimesogens.
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Affiliation(s)
- Emily E. Pocock
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK;
| | - Richard J. Mandle
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK;
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
| | - John W. Goodby
- Department of Chemistry, University of York, Heslington, York YO10 5DD, UK;
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Arakawa Y, Ishida Y, Tsuji H. Ether- and Thioether-Linked Naphthalene-Based Liquid-Crystal Dimers: Influence of Chalcogen Linkage and Mesogenic-Arm Symmetry on the Incidence and Stability of the Twist-Bend Nematic Phase. Chemistry 2020; 26:3767-3775. [PMID: 31825562 DOI: 10.1002/chem.201905208] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 12/05/2019] [Indexed: 11/11/2022]
Abstract
The twist-bend nematic (NTB ) phase with a heliconical nanostructure of the local director generating symmetry breaking by achiral bent-shaped molecules is a hot topic of current liquid-crystal science. As opposed to the most common methylene-linked dimers, this study demonstrates chalcogen ether- and/or thioether-linked 6-(4-cyanophenyl)-2-naphthyl-based liquid-crystal dimers with symmetric and asymmetric π-conjugated mesogenic-arm structures that exhibit the NTB phase. Although the symmetric bis(ether)-linked dimer exhibits only the conventional nematic (N) phase, the asymmetric bis(ether)-linked dimer can form the NTB phase. All thioether-linked dimers form the NTB phase, wherein the dimers with asymmetric arms vitrify in the NTB phase on cooling to room temperature. The phase transitions are discussed in terms of the chalcogen linkage combination, mesogenic-arm symmetry, and spacer length. It is revealed that thioether-linked dimers based on asymmetric π-conjugated mesogenic arms with terminal cyano groups are highly beneficial for the realization of materials that form a wide range of NTB phases and glassy NTB states at room temperature.
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Affiliation(s)
- Yuki Arakawa
- Department of Applied Chemistry and Life Science, Graduate School of Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, 441-8580, Japan
| | - Yuko Ishida
- Department of Applied Chemistry and Life Science, Graduate School of Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, 441-8580, Japan
| | - Hideto Tsuji
- Department of Applied Chemistry and Life Science, Graduate School of Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi, 441-8580, Japan
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Mandle RJ, Goodby JW. Molecular Flexibility and Bend in Semi-Rigid Liquid Crystals: Implications for the Heliconical Nematic Ground State. Chemistry 2019; 25:14454-14459. [PMID: 31483073 PMCID: PMC6899767 DOI: 10.1002/chem.201903677] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 09/03/2019] [Indexed: 11/12/2022]
Abstract
The NTB phase phases possess a local helical structure with a pitch length of a few nanometers and is typically exhibited by materials consisting of two rigid mesogenic units linked by a flexible oligomethylene spacer of odd parity, giving a bent shape. We report the synthesis and characterisation of two novel dimeric liquid crystals, and perform a computational study on 10 cyanobiphenyl dimers with varying linking groups, generating a large library of conformers for each compound; this allows us to present molecular bend angles as probability weighted averages of many conformers, rather than use a single conformer. We validate conformer libraries by comparison of interproton distances with those obtained from solution-based 1D 1 H NOESY NMR, finding good agreement between experiment and computational work. Conversely, we find that using any single conformer fails to reproduce experimental interproton distances. We find the use of a single conformer significantly overestimates the molecular bend angle while also ignoring flexibility; in addition, we show that the average bend angle and flexibility are both linked to the relative stability of the NTB phase.
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Mandle RJ, Goodby JW. A novel nematic-like mesophase induced in dimers, trimers and tetramers doped with a high helical twisting power additive. SOFT MATTER 2018; 14:8846-8852. [PMID: 30357232 DOI: 10.1039/c8sm01389f] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
From the observation of a previously undiscovered nematic-like mesophase (NX) by Archbold et al., we report on several new binary liquid-crystalline mixtures between the high helical twisting power dopant RM1041 and a selection of dimers with varying average bend angles and conformational landscapes. We also report on mixtures between RM1041 and oligomeric LC materials. We find that dimers and oligomers exhibit not only chiral nematic and twist-bend modulated phases, but also the same NX phase reported by Archbold, indicating that this state of matter (the structure of which is yet to be definitively characterised) is exhibited by a wide range of materials. Mixtures of the dimer CB9CB with a selection of different chiral dopants suggest that it is the helical twisting power of the chiral additive that is responsible incidence of the NX phase.
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