Ionic Liquid Crystals Based on Loop-Shaped Copper(I) Complexes.

This paper describes the synthesis and characterization of liquid crystals based on loop-shaped cationic copper(I) complexes of a multidentate ligand. Their synthesis involves the one-pot reaction of an alkyloxy-decorated pyridine-aldehyde unit with a diamine (2,2'-(ethylenedioxy)bis(ethylamine)) spacer to form in situ a pyridine-imine quadridentate-N4-donor ligand, L, which is able to chelate a copper(I) center associated with various noncoordinating anions. All of these compounds were characterized by NMR, IR, and electronic absorption spectroscopy, and more particularly by X-ray diffraction and mass spectroscopy, enabling unambiguous assignment of the [ML]+ mononuclear nature of the cationic components. The presence of six flexible alkyloxy chains at each end of the ligand associated with the rigidity of the core complex causes induction of a liquid crystal state with a columnar self-organized architecture, where the columns are packed in a hexagonal two-dimensional network.

Bistable spin-crossover in a new series of [Fe(BPP-R)2]2+ (BPP = 2,6-bis(pyrazol-1-yl)pyridine; R = CN) complexes.

Spin-crossover (SCO) active transition metal complexes are a class of switchable molecular materials. Such complexes undergo hysteretic high-spin (HS) to low-spin (LS) transition, and vice versa, rendering them suitable for the development of molecule-based switching and memory elements. Therefore, the search for SCO complexes undergoing abrupt and hysteretic SCO, that is, bistable SCO, is actively carried out by the molecular magnetism community. In this study, we report the bistable SCO characteristics associated with a new series of iron(ii) complexes-[Fe(BPP-CN)2](X)2, X = BF4 (1a-d) or ClO4 (2)-belonging to the [Fe(BPP-R)2]2+ (BPP = 2,6-bis(pyrazol-1-yl)pyridine) family of complexes. Among the complexes, the lattice solvent-free complex 2 showed a stable and complete SCO (T1/2 = 241 K) with a thermal hysteresis width (ΔT) of 28 K-the widest ΔT reported so far for a [Fe(BPP-R)2](X)2 family of complexes, showing abrupt SCO. The reproducible and bistable SCO shown by the relatively simple [Fe(BPP-CN)2](X)2 series of molecular complexes is encouraging to pursue [Fe(BPP-R)2]2+ systems for the realization of technologically relevant SCO complexes.

Ionic liquids at the surface of graphite: Wettability and structure.

The aim of this work is to provide a better understanding of the interface between graphite and different molecular and ionic liquids. Experimental measurements of the liquid surface tension and of the graphite-liquid contact angle for sixteen ionic liquids and three molecular liquids are reported. These experimental values allowed the calculation of the solid/liquid interfacial energy that varies, for the ionic liquids studied, between 14.5 mN m-1 for 1-ethyl-3-methylimidazolium dicyanamide and 37.8 mN m-1 for 3-dodecyl-1-(naphthalen-1-yl)-1H-imidazol-3-ium tetrafluoroborate. Imidazolium-based ionic liquids with large alkyl side-chains or functionalized with benzyl groups seem to interact more favourably with freshly peeled graphite surfaces. Even if the interfacial energy seems a good descriptor to assess the affinity of a liquid for a carbon-based solid material, we conclude that both the surface tension of the liquid and the contact angle between the liquid and the solid can be significant. Molecular dynamics simulations were used to investigate the ordering of the ions near the graphite surface. We conclude that the presence of large alkyl side-chains in the cations increases the ordering of ions at the graphite surface. Benzyl functional groups in the cations lead to a large affinity towards the graphite surface.

Intercalation synthesis of functional hybrid materials based on layered simple hydroxide hosts and ionic liquid guests--a pathway towards multifunctional ionogels without a silica matrix?

Functional hybrid materials on the basis of inorganic hosts and ionic liquids (ILs) as guests hold promise for a virtually unlimited number of applications. In particular, the interaction and the combination of properties of a defined inorganic matrix and a specific IL could lead to synergistic effects in property selection and tuning. Such hybrid materials, generally termed ionogels, are thus an emerging topic in hybrid materials research. The current article addresses some of the recent developments and focuses on the question why silica is currently the dominating matrix used for (inorganic) ionogel fabrication. In comparison to silica, matrix materials such as layered simple hydroxides, layered double hydroxides, clay-type substances, magnetic or catalytically active solids, and many other compounds could be much more interesting because they themselves may carry useful functionalities, which could also be exploited for multifunctional hybrid materials synthesis. The current article combines experimental results with some arguments as to how new, advanced functional hybrid materials can be generated and which obstacles will need to be overcome to successfully achieve the synthesis of a desired target material.

Mesomorphic imidazolium salts: new vectors for efficient siRNA transfection.

The preparation of chloride (1(n)) and bromide (2(n)) derivatives of 1-methyl-3-[3,4-bis(alkoxy)benzyl]-4H-imidazolium with n = 6, 12, 16, 18 is described. The two series of salts possess a rich thermotropic mesomorphism, chain-length dependent. Thus, a lamellar smectic A phase, a bicontinuous cubic Ia3d phase, and a columnar hexagonal liquid crystalline mesophase are induced as a function of increasing chain length. The mesomorphic properties were studied by polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction, and with the support of dilatometry and molecular dynamics, models for the various supramolecular arrangements of the salts are proposed. Such cationic amphiphiles were expected to be candidate molecules to design a new delivery reagent for nucleic acid transfection, particularly for short interfering RNA (siRNA). The use of an RNA interference mechanism, by introduction into cells by transfection of chemically synthesized siRNAs, is a powerful method for gene silencing studies. To exploit the potential of these amphilic imidazolium salts, these molecules were formulated with cohelper lipids and tested for their efficacy to deliver active siRNAs. Our results show high transfection efficacy of our formulated compounds and high silencing efficiency with more than 80% inhibition of the targeted gene at 10 nM siRNA concentration. Taken together our results show the potency of amphiphilic imidazolium salts as a new generation of transfection reagents for RNA interference.

1-(4-Alkyloxybenzyl)-3-methyl-1H-imidazol-3-ium organic backbone: a versatile smectogenic moiety.

The merger of ionic liquid and liquid crystal fields, obtained by using the imidazolium ring as a common element, has allowed us to tailor a new set of materials which associate specific functionalities. These functionalities are consequences of the original properties of the component, ionic liquids, liquid crystals and their association in a single compound. The study of this interesting association led us to elaborate environment-flexible cationic architectures from which mesomorphic properties emerge. Moreover, we have also explored the influence of different anions on the mesomorphic properties.

A convenient method for preparing rigid-core ionic liquid crystals.

An efficient, solvent free method for the N-arylation of imidazole by 1-(dodecyloxy)-4-iodobenzene using Cu(II)-NaY as catalyst and K(2)CO(3) as base is reported. By this synthetic approach, mesomorphic 3-[4-(dodecyloxy)phenyl]-1-methyl-1H-imidazol-3-ium iodide was synthesized in a two-step procedure, and its mesomorphism has been fully investigated by polarised optical microscopy, differential scanning calorimetry and X-ray diffraction. In addition its lamellar crystal structure, electrochemical behaviour and UV (absorption and emission) properties are reported.

Wormlike micelles from a cage amine metallosurfactant.

We have shown that copper and cobalt metallosurfactants derived from Cu(II) and Co(III) complexes of a macrobicyclic hexamine ("cage") can form wormlike micelles in aqueous solution that may coexist with or easily interconvert with vesicle structures. The cylindrical micelle structures are unusual for triple-chain surfactants with a single headgroup and are not easily accounted for using geometrical packing arguments. The solution behavior has been characterized by cryo-TEM and SAXS measurements. Both the Cu and Co compounds display viscoelastic solutions at 1 wt %, indicating that such behavior may be anticipated for the full variety of stable metal complexes formed by the cage headgroup, auguring applications based on the incorporation of metallo aggregates into mesoporous silica structures.

Selective oxidation of a single primary alcohol function in oligopyridine frameworks.

A variety of mono-oxidized pyridine, bipyridine, terpyridine, and pyridine/pyridazine are readily prepared under mild conditions using Pyrolusite MnO2. This phase has been characterized by means of X-ray powder diffraction and scanning electron microscopy. The oxidative activity is in keeping with the nature, morphology, and surface area of the MnO2 reagent.

Mesomorphic phenanthroline derivatives: novel architectures based on hydrogen bonding.

Strong hydrogen bonding has been observed in mesomorphic phenanthroline compounds engineered from diacylaminobenzene platforms: a columnar organization is found in the free ligands (n = 12 or 16) whereas a smectic arrangement is evidenced in a palladium complex (n = 16).

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.