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Accepted manuscript / Clean copy; International audience; Inspired by the supramolecular architecture of cornflower blue we developed luminescent flavylium salts with lipophilic alkoxy or thioether side chains which self-assemble into liquid crystalline phases. The current account highlights some fundamental aspects of our biological 'role model' anthocyanine, the origin of the natural pigment cornflower blue, and our recent developments on novel liquid crystalline emissive dyes. Starting with the general synthesis of flavylium salts, other topics address variations of flavylium ILCs, including specific tuning of their mesomorphic and photophysical behaviour.

Aminocyclopropenium ions have raised much attention as organocatalysts and redox active polymers. However, the self‐assembly of amphiphilic aminocyclopropenium ions remains challenging. The first deltic ionic liquid crystals based on aminocyclopropenium ions have been developed. Differential scanning calorimetry, polarizing optical microscopy and X‐ray diffraction provided insight into the unique self‐assembly and nanosegregation of these liquid crystals. While the combination of small headgroups with linear p‐alkoxyphenyl units led to bilayer‐type smectic mesophases, wedge‐shaped units resulted in columnar mesophases. Upon increasing the size and polyphilicity of the aminocyclopropenium headgroup, a lamellar phase was formed., Cyclopropenium‐based liquid crystals form lamellar or columnar mesophases, depending on the substitution of the head group and the number of peripheral chains. The effective volume of headgroup versus hydrophobic part determines the mesophase type. These compounds bridge the gap between low molecular weight organocatalysts and polymeric electrolytes based on cyclopropenium.

International audience; Two series of flavylium triflates carrying alkoxy side chains in the A-ring (benzo unit of chromylium salt) and thioethers in the B-ring (phenyl unit) (On-Fla-Sm) as well as thioethers at both A- and B-ring (Sn-Fla-Sm) were synthesized in order to understand the effect of thioether functionalization on their self-assembly and electronic properties. Concentration-dependent and diffusion ordered (DOSY) NMR experiments of O1-iV-Fla-S3 indicated the formation of columnar H-aggregates in solution with antiparallel intracolumnar stacking of the AC unit (chromylium) of the flavylium triflate, which agreed with the solid state structure of O1-V-Fla-S1 . Thioether substitution on the B-ring changed the linear optical properties in solution, while it has no effect on the A-ring. According to differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction bulk self-assembly of these ionic liquid crystals (ILCs) depends on the total number of side chains, yielding SmA and LamCol phases for ILCs with 2 - 3 chains and Colro, Colh phases for ILCs with 3 - 6 chains. Thus, we demonstrated that thioethers are a useful design tool for ILCs with tailored properties.

Thermotropic ionic liquid crystals based on the flavylium scaffold have been synthesized and studied for their structure‐properties relationship for the first time. The mesogens were probed by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X‐ray diffraction (XRD). Low numbers of alkoxy side chains resulted in smectic (SmA) and lamello‐columnar (LamCol) phases, whereas higher substituted flavylium salts showed Colro as well as ordered and disordered columnar (Colho, Colhd) mesophases. Mesophase width ranged from 13 K to 220 K, giving access to room temperature liquid crystals. The optical properties of the synthesized compounds were probed towards absorption and emission properties. Strong absorption with maxima between 444 and 507 nm was observed, and some chromophores were highly emissive with quantum yields up to 99 %. Ultimately, mesogenic and dye properties were examined by temperature‐dependent emissive experiments in the solid state., Flower power: In the search for new mesogenic cores for ionic liquid crystals, the authors were inspired by anthocyanidins, which are responsible for the bright red to blue colors in many plants. The new flavylium triflates were examined for their liquid crystalline and dye properties.

To combine liquid crystalline and linear optical properties in the same molecule, the fluorophobic effect was probed for the first time in donor acceptor dyes. Thus, a series of mono-, bi-, and tricyclic donor acceptor dyes with 1H,1H-perfluorinated alkyl chains of different lengths as donor units and nitrile, malononitrile or barbiturate as acceptor units was synthesized in 5 steps and 1.4-6.6 % overall yield. UV/Vis and fluorescence spectroscopy, cyclic voltammetry and DFT calculations revealed that absorption and emission maxima, Stokes shifts and LUMO energies were mainly governed by the chromophore size and acceptor strengths. The perfluorinated chain was electronically almost decoupled from the remaining chromophore and induced only slight changes of the absorption maxima as compared to the alkyl substituted counterparts. However, in contrast to the non-mesomorphic alkyl donor-substituted derivatives, the perfluorinated donors resulted in self-assembly into partially interdigitated SmA bilayers according to differential scanning calorimetry (DSC), polarizing optical microscopy (POM), X-ray diffraction (WAXS, SAXS) studies and electron density profile calculations.

The synthesis of a range of racemic 1-acyl-2-vinylcyclo­propanes by using two different methodologies is studied. We have developed a copper-catalyzed process for converting diazoketones into 1-acyl-2-vinylcyclopropanes and a sulfur-ylide-mediated procedure which allows, in only two steps, a simplified access to 1-acyl-2-vinyl­cyclopropanes with alkyl or aryl substituents on the alkene moiety.

International audience; A series of tetraguanidinium tetraphenylethene (TPE) arylsulfonates with different chain lengths was prepared via ionic self‐assembly of tetraguanidinium TPE chloride and the respective methyl arylsulfonates. Liquid crystalline properties were studied by differential scanning calorimetry, polarizing optical microscopy and X‐ray diffraction. Tetraguanidinium TPE arylsulfonates with chain lengths of C8–C12 displayed hexagonal columnar mesophases over a broad temperature range, while derivatives with longer chains showed oblique columnar phases. In solution all compounds displayed aggregation‐induced emission behaviour. Temperature‐dependent luminescence spectra of the bulk phase of the tetraguanidinium TPE arylsulfonate with C14 side chains revealed a strong luminescence both in the solid state and the oblique columnar mesophase. The emission behaviour was rationalized by a unique combination of restriction of intramolecular rotation of the TPE core, Coulomb interaction between the guanidinium cations and π–π interactions of the anionic arylsulfonate moieties.

A series of cyanobiphenyl dimers attached via alkoxy spacers to a central malonate were prepared, and the mesomorphic behaviour was studied by differential scanning calorimetry (DSC), polarised optical microscopy and X-ray diffraction (Wide-angle X-ray scattering and Small-angle X-ray scattering). Depending on spacer lengths and substitution of the malonate, nematic and smectic A mesophases with pronounced odd–even effect were observed. C-2-unsubstituted malonates formed nematic phases for chain lengths C6–C14, while C12 and C14 homologues displayed additional smectic A phases. In contrast, malonates with fluorinated tails at C-2 displayed exclusively smectic A phases. Remarkably, the X-ray diffraction profile of the smectic A phase of the C-2-unsubstituted C12 malonate showed a fundamental (001) and the corresponding third-order (003) diffraction peak, but no (002) reflection. Using Fourier analysis, the diffraction pattern was converted to an electron density profile, which was in good agreement with the proposed packing model of the SmA mesophase based on a horseshow- or hairpin-like conformation of the malonate.

International audience; Crown ethers and their derivatives are versatile building blocks for the design of supramolecular materials. They can be functionalized at will and are well known for their abilities to complex with alkali cations. Here, we show that emissive lanthanide free hybrid materials can be generated by using such building blocks. The organic tribenzo[18]crown-6 central core was functionalized via six-fold Suzuki cross-coupling as a key reaction with three o-terphenyl units which could be converted into their corresponding triphenylenes by the Scholl reaction, leading to novel liquid-crystalline columnar materials. Selected tribenzo[18]crown-6 o-terphenyls could interact with emissive ternary metal cluster compound salts to generate hybrid materials combining the properties of both moieties. Due to synergistic effects and despite the anisometry of the cluster compounds, individual properties such as liquid-crystalline phase stability of the organic part and emission abilities of its inorganic counter-part are enhanced in the hybrid compounds.

To probe the influence of electrostatic interactions on the mesomorphic self-assembly and phase behaviour of hybrid liquid crystals a series of crown ether/tyrosine hybrid systems was prepared by Steglich esterification of alkyl N-(tert-butoxycarbonyl)-L-tyrosinates with 4-carboxybenzo[15]crown-5 and 4-carboxybenzo[18]crown-6. The obtained derivatives allowed further manipulations at the NH functional group and complexation of the crown ether unit with NaI to give neutral or charged hybrid materials. All compounds were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (XRD) measurements. Neither the variation of the N-protecting group, introduction of charge at the N-terminus nor anion exchange (Cl vs. I) resulted in mesomorphism. In contrast, N-Boc-protected and unprotected hybrids formed rectangular columnar (Colr) mesophases with phase widths up to 35 K. NaI complexation switched these neutral thermotropic derivatives into ionic liquid crystals (ILCs) and induced a change of mesophase type from Colr to smectic A (SmA). A comparison of experimentally obtained layer distances and theoretically calculated molecular lengths indicated bilayer SmA formation with interdigitated alkyl chains. Packing models for both mesophase types are proposed and discussed with respect to stabilizing interactions.