Laurent Douce

Cation‐Induced Macroscopic Ordering of Non‐Mesomorphic Modules—A New Application for Metallohelicates

The subtle balance between organized and chaotic domains in the nondiscoidal ligand in the helicate 1, which displays liquid crystalline properties, represents the key element which enables the local molecular architecture to be integrated into an organized macroscopic ensemble.

π‐Stacked ortho‐Palladated Bipyridine Complexes Exhibiting Unusual Liquid Crystalline Behavior

A columnar structure with lamellar morphology in the liquid crystalline state is displayed by the palladium complex salt 1, which is synthesized from nonmesogenic ligands.

First assembly of copper(I) naphthyridine-based helicates

Copper(I) binds to 2,7-diimino-1,8-naphthyridine in solution n to form a mixture of equilibrating mono- and polynuclear complexes, n as identified by electrospray MS and monitored by UV-visible n spectrophotometric titrations, including a binuclear metallo-helicate n for which X-ray data are available but whose formation n does not require cooperative associations.

Synthesis and properties of a novel family of liquid crystalline building blocks based on 5,5′-substituted-2,2′-bipyridine

Abstract Novel liquid crystalline compounds based on 5-methyl-5′-(4-n-alkoxyphenylvinyl)-2,2′-bipyridine were synthesized and their mesomorphic properties investigated. All members of this series exhibit nematic, smectic A and smectic B phases. For the octyloxy compound an hexatic phase is also observed.

Columnar liquid crystals from wedge-shaped tetrahedral copper(I) complexes

Very stable copper(I) complexes were engineered from pyridine ligands bearing on one side an iminophenyl fragment and on the other a pivotal methyl group. The phenyl group was substituted in the para position either by a methoxy group or by a phenyl ester group grafted with three paraffin chains (n n= 8, 12, 16). The methoxy complex in the crystalline state was characterized by X-ray diffraction. Its molecular structure was found to correspond to a distorted tetrahedral arrangement round the copper(I) metal centre. The long-chain complexes near room temperature were found to produce columnar liquid crystals of hexagonal symmetry. The columns were found to result from the aggregation of the wedge-shaped molecules round the columnar axis with the metal-containing iminopicoline ligands crowded together in the centre and the alkyl chains pointing outwards with a disordered conformation. The degree of molecular aggregation, around 7, was found to decrease significantly on heating.

Liquid-crystalline metallo-helicates: New pathways for cooperative properties

Abstract Recent advances in the fields of liquid crystals and supramolecular chemistry have led to the discovery of mesomorphic metallo-helicates formed by selective complexation of non-mesomorphic oligopyridinic ligands built from flexible imino-appendages. Different types of mesophases, ranging from columnar to ordered smectic biaxial, have been generated. In cases where the segmented ligand is adequately engineered, gliding of the coordinated ligands across the metal centers present in the emergent dinuclear complex is made possible by the provision of ancillary imino binding sites and this behavior facilitates liquid-crystalline properties at room-temperature, after supercooling. Furthermore, formation of a mesogenic mixed-valence complex following selective oxidation has been realized. An attempt is made to provide insight on how the strategy of using imino-based oligopyridinic scaffolds permits generation of liquid-crystalline materials with morphologies determined by their molecular components.

5,5′-Substituted-2,2′-bipyridines: A new series of liquid crystalline materials

Abstract Dissymmetric functionalization of 5,5′-dimethyl-2,2′-bipyridine with a ‘stilbene type’ chromophore bearing a terminal alkoxy group leads to a new family of mesomorphic compounds exhibiting a rich thermotropic polymorphism. A succession of smectic B, smectic A and nematic phases was observed. For the octyloxy compound, an additional phase was detected which was hexatic in symmetry.

Preliminary Communications Thermotropic liquid crystal behaviour of 5,5′-[(4-hexadecyloxyphenyl)ethynyl]-2,2′-bipyridine

Abstract 5,5′-[(4-Hexadecyloxyphenyl)ethynyl]-2,2′-bipyridine was synthesized by a palladium(O) cross-coupling reaction. Its thermotropic liquid crystalline behaviour was analysed using differential scanning calorimetry, polarizing microscopy, and X-ray diffraction. Three enantiotropic tilted smectic phases were identified upon heating: SF, SI, and SC.

Über π-π-Wechselwirkungen gestapelte „ortho-palladierte” Komplexe mit Bipyridinliganden und ungewöhnlichem flüssigkristallinen Verhalten

Eine columnare Struktur mit lamellarer Morphologie zeigt im flussigkristallinen Zustand das Palladiumkomplexsalz 1, das aus nicht mesogenen Liganden hergestellt wird.

A facile route to multi-functionalization of methyl gallate: pivotal synthons for mesomorphic materials

Abstract The preparation of mono-, di- and trisubstituted gallic derivatives is described using either 1-bromododecane or 12-bromo-1-dodecanol. After saponification of the methyl ester bearing the dodecanol groups, subsequent functionalization with methacryloyl chloride provides the hybrid methacrylate esters/anhydride species. Selective cleavage of the anhydride function gives rise to the corresponding acids, which have been further functionalized to the imine derivative 15 by condensation with 4-[imino-4-(toluyl)]phenol. This reaction is made possible using the acidic form of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC·HCl) and dimethylaminopyridine (DMAP). Selective hydrolysis of the imine function with a HCl-treated silica provides the targeted aniline in excellent yield.