Redox-active dithiolated tetrathiafulvalene derivatives (TTFdT) were inserted in two-dimensional nanoparticle arrays to build interlinked networks of molecular junctions. Upon oxidation of the TTFdT to the dication state, we observed a conductance increase of the networks by up to 1 order of magnitude. Successive oxidation and reduction cycles demonstrated a clear switching behavior of the molecular junction conductance. These results show the potential of interlinked nanoparticle arrays as chemical sensors.

TpRu(PPh3)(CH3CN)2 PF6 (10 mol %) catalyst effected the nucleophilic addition of water, alcohols, aniline, acetylacetone, pyrroles, and dimethyl malonate to unfunctionalized enediynes under suitable conditions (100 degrees C, 12-24 h) and gave functionalized benzene products in good yields. In this novel cyclization, nucleophiles very regioselectively attack the internal C1' alkyne carbon of enediynes to give benzene derivatives as a single regioisomer. Experiments with methoxy substituents exclude the possible involvement of naphthyl cations as reaction intermediates in the cyclization of (o-ethynylphenyl) alkynes. Deuterium-labeling experiments indicate that the catalytically active species is ruthenium-pi-alkyne rather than ruthenium-vinylidene species. This hypothesis is further confirmed by the aromatization of o-(2'-iodoethynyl)phenyl alkynes with alcohols. We propose a nucleophilic addition/insertion mechanism for this nucleophilic aromatization on the basis of a series of experiments.

PtCl2 (5 mol%) is an effective catalyst for aromatization of enediynes via a C-H bond insertion of tethered alkanes. The reaction mechanism of this cyclization is proposed to involve platinum-pi-alkyne intermediates. This cyclization works not only for terminal alkynes but also for internal alkynes.

Silica nanoparticles of 12 nm diameter were surface-doped with ca. 350 (TTF-dppz)Yb(III) surface species, containing bis(propylthio)tetrathiafulvenyl[i]dipyrido-[3,2a:2′,3-c]phenazine (TTF-dppz) as an antenna ligand through a surface organometallic chemistry approach. These nanoparticles absorb and emit in the NIR (λ abs = 750 nm, λ em = 983 and 1050 nm) with a lifetime (τ 1 ) of 2.8 μs, similarly to the corresponding Yb(III) molecular complex (λ abs = 750 nm, λ em = 975, 986, 1009, and 1020 nm with τ 1 = 6.93 μs). The silica materials were fully characterized using combined spectroscopic techniques (IR, NMR, UV−vis, luminescence and lifetime), molecular models and isostructural diamagnetic yttrium-containing materials for easier characterization by NMR spectroscopy. Having established the surface structures and photophysical properties of these nanoparticles, we transposed this methodology to larger silica particles with a diameter of ca. 100 nm. These larger nanoparticles have similar photophysical properties and contain ca. 30 000 chromophores, making possible one-photon NIR-to-NIR emission optical microscopy imaging of single nanoparticles.

The self-assembly of organic molecules at liquid/solid interfaces has attracted particular attention in recent years for the rational design and fabrication of functional surfaces with unique electrical, optical and catalytic properties. [1][2][3] Surface deposition at solid/liquid interfaces is driven by the delicate interplay of the adsorbate with itself, the substrate, as well as interactions of both with the solvent. This interplay involves basic concepts of 2D crystal engineering, such as hydrogen bonding, [4] p-p stacking, [5] metal-ligand coordination [6] and van der Waals interactions. [1, 2,7] Scanning probe microscopy (SPM) is a unique nanoscience tool to address structures and electronic properties of molecular ensembles and single molecules with unprecedented resolution in real space and time. Investigations at (electrified) liquid/solid interfaces enable the construction of equilibrated self-assembled monolayers or more complex hierarchical architectures, and to address their functionalities in a well-controlled environment. Scanning tunnelling spectroscopy (STS) as applied to the liquid/solid interphases is capable of detecting in situ local changes in the electronic properties of molecules, [1c] resulting, for example, from intermolecular donor-acceptor (D-A) or charge-transfer interactions. [8a-d] Herein, we report the first in situ scanning tunnelling microscopy (STM) and spectroscopy (STS) study on the selfassembly of a new class of p-conjugated bifunctional tri-star molecules (Scheme 1), [9] physisorbed from solution on highly oriented pyrolitic graphite (HOPG) under ambient conditions. We also demonstrate, based on STS measurements, that the molecular system exhibits a pronounced rectification response.The redox-active and chromophoric D-A target molecules 1 a-d (Scheme 1 and the Supporting Information) represent planar, fused p-conjugated systems of high symmetry, which were obtained by annulation of three functionalised tetrathiafulvalene (TTF) subunits with a hexaazatriphenylene (HAT) core. The TTF building block is a strong p-electron donor (D) [10] and the annulated electron-deficient HAT system acts as an acceptor (A) unit.[11] The extended p-conjugated molecules (TTF-HAT) are terminally substituted with six symmetrically arranged and rather flexible thioalkyl groups of variable length. Specifically, compounds 1 a-d were obtained by a direct condensation reaction of hexaketocyclohexane with 5,6-diamino-2-(4,5-bis(alkylthio)-1,3-dithio-2-ylidene)benzo[d]-1,3-dithiole. The latter was prepared by a phosphite-mediated cross-coupling reaction of 4,5-bis(alkylthio)-1,3-dithiole-2-one with 5,6-diaminobenzene-1,3-dithiole-2-thione.[9] All compounds were purified by chromatographic separation and have been fully characterised (see the Supporting Information). The covalent linkage between the molecular electron-donor and electron-ac- [a] Dr.