Liquid-crystalline dendrons carrying either a thiol or disulfide function which display nematic, smectic A, columnar, or chiral nematic phases have been synthesized. Their mesomorphic properties are in agreement with the nature of the mesogenic units and structure of the dendrons. The first-generation poly(aryl ester) dendron containing two cyanobiphenyl mesogenic units was used to functionalize gold nanoparticles. For full coverage, a smectic-like supramolecular organization on the nanometer scale is observed, when the gold nanoparticles are spread onto carbon-coated copper grids. This result indicates that the dendritic ligands reported here act as self-organization promoters.Introduction. -Rational design of novel supramolecular materials for applications in optics, electronics, catalysis, and biomedical sciences is still a challenge [1], current interest with this aim being focused on the synthesis of thermotropic liquid-crystalline gold nanoparticles [2 -5]. Decorated gold nanoparticles are one of the most promising candidates for self-organization leading to bulk metamaterials, i.e., materials with nonconventional electromagnetic properties. It has already been shown that regular arrangements of metallic particles on different length scales can lead to negative magnetic permeability [6]. This opens the pathway to metamaterials in the visible light region, provided that the following conditions are fulfilled: the distance and organization of the particles have to be controlled, and there should be a possibility to compensate optical absorption by incorporation of active agents to allow energy transfer [7]. The first condition is fulfilled by the self-organization within the liquidcrystal phase itself, while the second one can be fulfilled by adding fluorescence dyes into the liquid-crystal materials.To generate mesomorphism, gold nanoparticles were functionalized with liquidcrystalline thiol derivatives [2 -4] via a ligand-exchange reaction from dodecane-1-thiol-stabilized gold nanoparticles [8]. Only in one case, the mesophase displayed by the materials could be identified [4]: an enantiotropic nematic phase was obtained for gold nanoparticles partly decorated with laterally-branched mesogens; the latter

Dinuclear ruthenium complexes containing the stable metal−metal bonded Ru2(CO)4 sawhorse unit with two dendritic carboxylato bridges have been synthesized and characterized. All complexes Ru2(CO)4(O2CR)2L2 (R = R1, R2, R3) containing cyanobiphenyl-based poly(arylester) dendrons of first (R1), second (R2), and third (R3) generation and triphenylphosphine, pyridine, or 4-picoline ligands L proved to be mesomorphic, giving rise to smectic A or smectic A and nematic phases. The supramolecular organization within the smectic A phase is governed by the nature and structure of the mesogenic units and dendritic core. Such materials are of interest for the design of catalytically active anisotropic fluids.

Fluorescent mesomorphic materials have been synthesized by grafting difluoro-bora-diaza-s-indacene (FBodipy) onto first-, second-, and third-generation liquid-crystalline poly(aryl ester) dendrons functionalized with cyanobiphenyl units. The second-and third-generation dendrimers give rise to smectic A phases; the firstgeneration dendrimer shows a nematic phase and an unidentified phase. The supramolecular organization within the smectic A phase could be established from X-ray experiments: the dendritic core is oriented approximately parallel to the layer planes and the mesogenic units are oriented perpendicularly above and below the dendritic core; interdigitation occurs between neighboring layers. All the materials are highly fluorescent both in solution and in the mesophases. For the first-generation dendrimer, the formation of J-aggregates was detected. The higher-generation dendrons prevented the formation of aggregates. Therefore, the dendrons play the role of liquid-crystalline promoters and protective shells.