Luminescent assemblies of pyrene-containing bent-core mesogens: liquid crystals, π-gels and nanotubes

Ros, M. Blanca; Martínez‐Abadía, Marta; Varghese, Shinto; Gierschner, Johannes; Giménez, Raquel

doi:10.1039/d2tc02546a

Cited by 8 publications

(4 citation statements)

References 109 publications

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“…However, despite considerable experimental effort, the biaxial N phase has remained elusive, with no undisputable evidence reported until now for low-molecular-weight calamitic LCs [ 3 , 4 ]. Over the last two decades, bent-core mesogens (BCMs), a class of compounds featuring a kinked aromatic core between two terminal aliphatic tails, have attracted considerable interest for the formation of a variety of exotic mesophases and self-assembled supramolecular structures [ 5 , 6 , 7 , 8 ], as well as for the exhibition of a possibly biaxial N phase [ 5 , 9 , 10 , 11 ]. Although the occurrence of spontaneous macroscopic biaxiality in nematic BCMs has been questioned, strong experimental evidence suggests the presence of local biaxial (and possibly polar) order within nanosized clusters of stratified molecules (known as cybotactic groups) which permeate the N phase.…”

Section: Introductionmentioning

confidence: 99%

Macroscopic Biaxial Order in Multilayer Films of Bent-Core Liquid Crystals Deposited by Combined Langmuir–Blodgett/Langmuir–Schaefer Technique

Vita,

Adamo,

Campana

et al. 2024

Nanomaterials

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Bent-core liquid crystals, a class of mesogenic compounds with non-linear molecular structures, are well known for their unconventional mesophases, characterized by complex molecular (and supramolecular) ordering and often featuring biaxial and polar properties. In the nematic phase, their unique behavior is manifested in the formation of nano-sized biaxial clusters of layered molecules (cybotactic groups). While this prompted their consideration in the quest for nematic biaxiality, experimental evidence indicates that the cybotactic order is only short-ranged and that the nematic phase is macroscopically uniaxial. By combining atomic force microscopy, neutron reflectivity and wide-angle grazing-incidence X-ray scattering, here, we demonstrate that multilayer films of a bent-core nematic, deposited on silicon by a combined Langmuir–Blodgett and Langmuir–Schaefer approach, exhibit macroscopic in-plane ordering, with the long molecular axis tilted with respect to the sample surface and the short molecular axis (i.e., the apex bisector) aligned along the film compression direction. We thus propose the use of Langmuir films as an effective way to study and control the complex anchoring properties of bent-core liquid crystals.

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Section: Introductionmentioning

confidence: 99%

Macroscopic Biaxial Order in Multilayer Films of Bent-Core Liquid Crystals Deposited by Combined Langmuir–Blodgett/Langmuir–Schaefer Technique

Vita,

Adamo,

Campana

et al. 2024

Nanomaterials

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“…At first, 1-functionalized pyrene was reported to produce dimeric liquid crystals, symmetrical and non-symmetrical, and to yield essentially nematic (also including the so-called twist–bend nematic) and smectic phases [ 22 , 23 , 24 , 25 ]. Pyrene was also inserted in cyclophanes (via 1,6-positions), i.e., pyrenophanes, also yielding a nematic phase [ 26 , 27 , 28 ], as well as in polycatenars [ 29 ] and, recently, in some bent-core mesogens [ 30 ], for which columnar mesophases were systematically induced. Dendrimers bearing apical mono- and disubstituted pyrene moiety [ 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ] have also been reported to self-organize into columnar and cubic mesophases.…”

Section: Introductionmentioning

confidence: 99%

Pyrene-Fused Poly-Aromatic Regioisomers: Synthesis, Columnar Mesomorphism, and Optical Properties

et al. 2023

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π-Extended pyrene compounds possess remarkable luminescent and semiconducting properties and are being intensively investigated as electroluminescent materials for potential uses in organic light-emitting diodes, transistors, and solar cells. Here, the synthesis of two sets of pyrene-containing π-conjugated polyaromatic regioisomers, namely 2,3,10,11,14,15,20,21-octaalkyloxypentabenzo[a,c,m,o,rst]pentaphene (BBPn) and 2,3,6,7,13,14,17,18-octaalkyloxydibenzo[j,tuv]phenanthro [9,10-b]picene (DBPn), is reported. They were obtained using the Suzuki–Miyaura cross-coupling in tandem with Scholl oxidative cyclodehydrogenation reactions from the easily accessible precursors 1,8- and 1,6-dibromopyrene, respectively. Both sets of compounds, equipped with eight peripheral aliphatic chains, self-assemble into a single hexagonal columnar mesophase, with one short-chain BBPn homolog also exhibiting another columnar mesophase at a lower temperature, with a rectangular symmetry; BBPn isomers also possess wider mesophase ranges and higher mesophases’ stability than their DBPn homologs. These polycyclic aromatic hydrocarbons all show a strong tendency of face-on orientation on the substrate and could be controlled to edge-on alignment through mechanical shearing of interest for their implementation in photoelectronic devices. In addition, both series BBPn and DBPn display green-yellow luminescence, with high fluorescence quantum yields, around 30%. In particular, BBPn exhibit a blue shift phenomenon in both absorption and emission with respect to their DBPn isomers. DFT results were in good agreement with the optical properties and with the stability ranges of the mesophases by confirming the higher divergence from the flatness of DBPn compared with BBPn. Based on these interesting properties, these isomers could be potentially applied not only in the field of fluorescent dyes but also in the field of organic photoelectric semiconductor materials as electron transport materials.

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“…[22][23][24] As a kind of excellent supramolecular self-assembly, chiral luminous liquid crystal (LC) is the optimal medium to produce chiral amplification due to the long-range ordered structure. [25][26][27] In this self-assembly process, LC can enhance the chirality, even transfer this chirality to the nonchiral fluorophore, which induces circular dichroism (CD) and CPL features. [28][29][30] If the external environment changes, CPL materials not only show high g lum but also present different colors for wavelength adjustment, which can further greatly enrich their applications.…”

Section: Introductionmentioning

confidence: 99%

“…Especially, AIE‐active molecule is employed for supramolecular self‐assembly, which can dramatically increase the luminescence asymmetry factor (g lum ) of the CPL materials [22–24] . As a kind of excellent supramolecular self‐assembly, chiral luminous liquid crystal (LC) is the optimal medium to produce chiral amplification due to the long‐range ordered structure [25–27] . In this self‐assembly process, LC can enhance the chirality, even transfer this chirality to the nonchiral fluorophore, which induces circular dichroism (CD) and CPL features [28–30] …”

Section: Introductionmentioning

confidence: 99%

Highly Efficient Wavelength‐Tunable Circularly Polarized Luminescence Film Constructed by Responsive Chiral Aggregation‐induced Emission Luminophore

Luo

Huang

Deng

et al. 2023

Chemistry A European J

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Key Lab of Environment‐friendly Chemistry and Circularly polarized luminescent (CPL) materials with multitudinous inherent advantages shows extensive application. In this work, we prepare a kind of highly efficient wavelength‐tunable CPL free‐standing films by responsive chiral aggregation‐induced emission mesogen. Firstly, the pyridine‐functionalized tetraphenylethene monomer (MPy) is designed and synthesized. Then, the different ration of the monomer MPy mixed with the liquid crystal (LC) reactive monomer (LC242) to fabricate a free‐standing film by photopolymerization. The obtained film presents efficient CPL with a constant luminescence asymmetry factor (glum) of +0.75, as well as sensitive wavelength tunability. Finally, this wavelength‐tunable CPL film with both fluorescence and CPL modes is successfully applied in anti‐counterfeiting and information encryption. This work provides a simple way to construct CPL apparatus with adjustable luminescence wavelength and high glum.

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Luminescent assemblies of pyrene-containing bent-core mesogens: liquid crystals, π-gels and nanotubes

Abstract: Bent-shaped molecules incorporating terminal pyrene moieties were designed and synthesized aiming at promoting a variety of luminescent self-assembled materials. The novel compounds are fluorescent both in solution and in condensed...

Cited by 8 publications

References 109 publications

Macroscopic Biaxial Order in Multilayer Films of Bent-Core Liquid Crystals Deposited by Combined Langmuir–Blodgett/Langmuir–Schaefer Technique

Macroscopic Biaxial Order in Multilayer Films of Bent-Core Liquid Crystals Deposited by Combined Langmuir–Blodgett/Langmuir–Schaefer Technique

Pyrene-Fused Poly-Aromatic Regioisomers: Synthesis, Columnar Mesomorphism, and Optical Properties

Highly Efficient Wavelength‐Tunable Circularly Polarized Luminescence Film Constructed by Responsive Chiral Aggregation‐induced Emission Luminophore

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