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

Proof that sulfur is a viable reporting element for the development of fluorescent chemosensors for metal ions is presented. To date, the majority of metal-responsive fluorescent chemosensors have relied on metal-nitrogen coordination to provide a fluorescence response, most commonly by suppressing photoinduced electron transfer (PET) quenching. While chemosensors with direct application to biology, medicine, and analytical chemistry have been so developed, reliance on the coordination chemistry of nitrogen remains a practical and conceptual limitation. Building on the fact that thioureas can quench fluorescence emission by PET, it is shown that the quenched emission of thiourea-appended naphthalimides can be restored by metal binding and that metal affinity and selectivity can be controlled through structural modification of the thiourea substituents. Further, such chemosensors can function in aqueous media and, unlike nitrogen-based chemosensors, are unresponsive to increases in [H(+)]. Given that the coordination properties of sulfur are distinct from those of nitrogen, this work lays the foundation for the development of a new class of interesting and useful metal-responsive fluorescent probes.

We describe three significant advances in the use of thioureas as reporting elements for metalresponsive fluorescent chemosensors. First, on the basis of the crystal structure of a chemosensor analogue, we provide a deeper understanding of the details of the thiourea coordination environment. Second, we describe a new generation of chemosensors with higher affinities for Zn2+ and Cd2+ than were observed for earlier probes, expanding the scope of this type of probe beyond Hg2+ detection. Third, we show that a thiourea-based chemosensor can be employed for fluorescence microscopy imaging of Hg2+ ion concentrations in living mammalian cells.

Two new bipyridine ligands containing, respectively, two and four pyrene units were prepared.The obtained compounds were employed to synthesize new pyrene labeled ruthenium (II) trisbipyridine complex as well as a pyrene labeled ruthenium (II) trisbipyridine cored dendrimer.The obtained bipyridine ligands and the ruthenium complexes were characterized by NMR spectroscopy and MALDI-TOF mass spectroscopy. The optical and photophysical properties of the luminescent macromolecules were studied by absorption and fluorescence spectroscopy. It was noticed that the absorption spectra of the obtained complexes correspond to the sum of the absorption spectra of their components, which indicates a lack of interaction in the ground state.Efficient energy transfer was observed from pyrene units to the metal complex core resulting in the observation of the characteristic ruthenium bipyridine emission band upon excitation at the pyrene absorption wavelength. Moreover, efficient protection to oxygen quenching was remarked in the first generation dendrimer.