Understanding the remarkable difference in liquid crystal behaviour between secondary and tertiary amides: the synthesis and characterisation of new benzanilide-based liquid crystal dimers

Strachan, Grant J.; Harrison, William T. A.; Storey, John M. D.; Imrie, Corrie T.

doi:10.1039/d1cp01125a

Cited by 15 publications

(13 citation statements)

References 63 publications

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“…The 1 H chemical shifts of the 2°benzanilide-based dimers are consistent with these materials being present entirely in the Z conformation in solution, as has been reported for similar compounds. [5] However, the 1 H NMR spectra of the ortho substituted 3°benzanilides indicates the presence of two diastereotopic conformers, identified as the E and Z amide conformations (Figure 3). The ratio of the conformers was dependent on the number and position of methyl substituents (Table 1).…”

Section: Amide Conformationmentioning

confidence: 99%

“…) and these values are in good agreement with the single rotational barrier reported previously. [5] Although the amide rotational barrier can be affected by the solvent, no significant difference could be seen in this measurement. Reported rotational barriers for ortho substituted amides in CDCl 3 and DMSO-d 6 have been reported to differ by less than 1.5 kJ mol À 1 when the ortho substituent is not capable of hydrogen bonding interactions.…”

Section: Chemphyschemmentioning

confidence: 99%

“…The higher melting point of 2 a compared to 1 a [A] This compound has been reported previously. [5] [B] Denotes values taken from POM. [C] Step change in baseline seen in DSC cooling trace.…”

Section: Phase Behaviour Of Secondary Benzanilides 1 A-5 Amentioning

confidence: 99%

“…While a decrease in the transition temperatures would be expected on going to from 2°t o 3°benzanilides, due to the loss of hydrogen bonding, comparisons between analogous amide and ester-linked liquid [A] This compound has been reported previously. [5] [B] Denotes values taken from DSC cooling trace. ChemPhysChem crystals suggests that this would correspond to a decrease of 30-40 °C.…”

Section: Phase Behaviour Of 3°benzanilides With An N-methyl Group 1 B...mentioning

confidence: 99%

“…[4] It was assumed that this reflected the disruption of hydrogen bonding in these systems, but we have shown recently that the 3°benzanilides adopt the highly non-linear E conformation and this accounts for the absence of liquid crystalline behaviour. [5] Judicious molecular design, however, allowed us to overcome this issue and we reported liquid crystalline 3°benzanilides.…”

Section: Introductionmentioning

confidence: 99%

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Using Lateral Substitution to Control Conformational Preference and Phase Behaviour of Benzanilide‐based Liquid Crystal Dimers

et al. 2022

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The inclusion of secondary and tertiary benzanilide-based mesogenic groups into liquid crystal dimers is reported as a means to develop new materials. Furthermore, substitution at the nitrogen atom is shown to introduce an additional synthetic 'handle' to modify the molecular structure of the tertiary materials. The design of these materials has proved challenging due to the strong preferences of 3°benzanilides for the E amide conformation. In this work, lateral substitution is used to modify the conformational preferences of the amide linkage and promote liquid crystallinity for a series of N-methyl benzanilide dimers. As the proportion of the E conformer decreases, the nematic-isotropic transition temperatures increase, and enantiotropic nematic behaviour is observed. We also report the synthesis and characterisation of the analogous 2°benzanilidebased materials, which show nematic and twist-bend nematic behaviour. This approach highlights the effects that seemingly small structural modifications, such as the inclusion and position of a methyl group, can have on molecular shape and hence, liquid crystalline behaviour.

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Section: Amide Conformationmentioning

confidence: 99%

Section: Chemphyschemmentioning

confidence: 99%

Section: Phase Behaviour Of Secondary Benzanilides 1 A-5 Amentioning

confidence: 99%

Section: Phase Behaviour Of 3°benzanilides With An N-methyl Group 1 B...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Using Lateral Substitution to Control Conformational Preference and Phase Behaviour of Benzanilide‐based Liquid Crystal Dimers

et al. 2022

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Supramolecular liquid crystals from the dimer of L‐shaped molecules with tertiary amide end groups

Sawatari,

Shimomura,

Takeuchi

et al. 2024

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Supramolecular liquid crystals (SLCs) are attractive materials for fabricating devices with new optoelectronic functions. Conventional SLCs are made from hydrogen‐bonded mesogens. However, these mesogens suffer from high melting points, and the types of formable aggregates are limited owing to the directionality of the hydrogen bonding. Therefore, to fabricate non‐hydrogen‐bonded SLCs, we hypothesized that the introduction of tertiary amide groups into calamitic molecules would be advantageous because they have an L‐shaped structure with N‐ or C‐alkyl side chains not aligned along the long axis and the flexibility to undergo cis–trans isomerization. In this study, we developed a novel non‐hydrogen‐bonded SLC by assembling an L‐shaped dimer composed of calamitic molecules (phenyltolanes) with tertiary amides at their ends. These molecules exhibited a smectic B phase. The phase transition temperature of the SLCs from crystal to liquid crystal phase was low despite the long π‐conjugated core. Wide‐angle X‐ray diffraction and variable‐temperature Fourier‐transform infrared measurements revealed dimer formation by weak intermolecular interactions, that is, the molecular recognition of L‐shaped molecules, and mobility of the alkyl groups attached to amide driven by cis–trans isomerization in the liquid crystal phase. Thus, cis–trans isomerization of tertiary amides contributed enormously to the formation and lower clearing points of this SLC. The developed method can be used not only to develop non‐hydrogen‐bonded SLCs but also to develop novel soft matter with controlled properties by incorporating the SLCs, as the aggregates can be controlled to impart desired functionalities.

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The Emergence of a Polar Nematic Phase: A Chemist's Insight into the Ferroelectric Nematic Phase

Cruickshank

2024

ChemPlusChem

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The discovery of a new polar nematic phase; the ferroelectric nematic, has generated a great deal of excitement in the field of liquid crystals. To date there have been around 150 materials exhibiting the ferroelectric nematic phase, in general following three key archetypal structures with these compounds known as RM734, DIO and UUQU‐4N. In this review, the relationship between the molecular structure and the stability of the ferroelectric nematic, NF, phase will be described from a chemist’s perspective. This will look to highlight the wide variety of functionalities which have been incorporated into these archetypal structures and how these changes influence the transition temperatures of the mesophases present. The NF phase appears to be stabilised particularly by reducing the length of terminal alkyl chains present and adding fluorines laterally along the length of the molecular backbone. This review will look to introduce the background of the ferroelectric nematic phase before then showing the molecular structures of a range of materials which exhibit the phase, describing their structure‐property relationships and therefore giving an up‐to‐date account of the literature for this fascinating new mesophase.

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Understanding the remarkable difference in liquid crystal behaviour between secondary and tertiary amides: the synthesis and characterisation of new benzanilide-based liquid crystal dimers

Abstract: A number of liquid crystal dimers have been synthesised and characterised containing secondary or tertiary (N-methyl) benzanilide-based mesogenic groups. The secondary amides all form nematic phases, and we present the...

Cited by 15 publications

References 63 publications

Using Lateral Substitution to Control Conformational Preference and Phase Behaviour of Benzanilide‐based Liquid Crystal Dimers

Using Lateral Substitution to Control Conformational Preference and Phase Behaviour of Benzanilide‐based Liquid Crystal Dimers

Supramolecular liquid crystals from the dimer of L‐shaped molecules with tertiary amide end groups

The Emergence of a Polar Nematic Phase: A Chemist's Insight into the Ferroelectric Nematic Phase

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