Syntheses and photophysical properties of visible-light-absorbing Ru(II) polypyridyl complexes possessing (pyridylpyrazolyl)metal tethers

Novel Ru(II) polypyridyl complexes possessing pyridylpyrazolyl tethers were synthesized. Reactions with various organometallic precursors readily afforded multinuclear complexes which possess a light-harvesting Ru(II) core and (pyridylpyrazolyl)metal fragments in high yields. Analysis of the photophysical properties of the obtained multinuclear complexes revealed that the complexes had similar absorption and emission characteristics; however, their emission quantum yields decreased in proportion to the number of metal fragments. The di- and trinuclear complexes were stable under donating solvent such as CH₃CN.     

Organic high-spin systems: Synthesis,electrochemical and spectroscopic studies of π-extended tetraaryl m-phenylenediamines

Three highly π-extended tetraaryl-1,3-phenylenediamines for charged high-spin molecular systems were successfully synthesized using Suzuki coupling. Their electrochemical and spectroscopic properties were also examined. They showed blue fluorescence. The dications derived from highly π-extended tetraaryl-1,3-phenylenediamines were generated and characterized by electron transfer stopped-flow method.     

New approach to oligotriazoles using a cobalt complex of propargyl azides as a synthetic component

We have developed an efficient method for preparation of triazolamers using a dicobalt hexacarbonyl complex of propargyl azides (CPA) as a synthetic component. Several types of CPAs possessing the side chains found in the natural amino acids were prepared by Nicholas reaction as well as by a reaction of propargyl azides with dicobalt octacarbonyl. Triazolamers with both amino and carboxyl termini were readily synthesized by repetitive reaction sequence involving a copper-catalyzed 1,3-dipolar cycloaddition followed by an oxidative deprotection.     

Reaction of alkynyltrimethylsilanes with a hypervalent organoiodine compound: A new general synthesis of alkynyliodonium salts

New general methods for the synthesis of alkynyl(phenyl)iodonium tetrafluoroborate 2 from alkynyltrimethylsilanes 1 utilizing the combination of iodosylbenzene and triethyloxonium tetrafluoroborate or boron trifluoride etherate were developed. The medium effect observed in the reaction was also discussed.     

Electrochemical properties of core-shell TiC-TiO2 nanoparticle films immobilized at ITO electrode surfaces

Titanium carbide (TiC) nanoparticles are readily deposited onto tin-doped indium oxide (ITO) electrodes in the form of thin porous films. The nanoparticle deposits are electrically highly conducting and electrochemically active. In aqueous media (at pH 7) and at applied potentials positive of 0.3 V vs. SCE partial anodic surface oxidation and formation (at least in part) of novel core-shell TiC-TiO2 nanoparticles is observed. Significant thermal oxidation of TiC nanoparticles by heating in air occurs at a temperature of 250 degrees C and leads first to core-shell TiC-TiO2 nanoparticles, next at ca. 350 degrees C to TiO2 (anatase), and finally at temperatures higher than 750 degrees C to TiO2 (rutile). Electrochemically and thermally partially oxidized TiC nanoparticles still remain very active and for some redox systems electrocatalytically active. Scanning and transmission electron microscopy (SEM and TEM), temperature dependent XRD, quartz crystal microbalance, and voltammetric measurements are reported. The electrocatalytic properties of the core-shell TiC-TiO2 nanoparticulate films are surveyed for the oxidation of hydroquinone, ascorbic acid, and dopamine in aqueous buffer media. In TiC-TiO2 core-shell nanoparticle films TiO2 surface reactivity can be combined with TiC conductivity.     

Seed-mediated growth of palladium nanocrystals on indium tin oxide surfaces and their applicability as modified electrodes

Palladium nanoparticles (PdNPs) were successfully attached and grown on an indium tin oxide (ITO) surface using a seed-mediated growth method, i.e., via a simple two-step immersion of the ITO substrate into the seed and growth solutions. After the growth treatment for 24 h, PdNPs grew up to 60-80 nm, exhibiting crystal-like appearances and accompanying the formation of short rodlike nanocrystals as a minor product. Thus prepared PdNPs tend to stick each other, so that the dense gathering of PdNPs was observed on the ITO surfaces. Due to the dense attachment, the PdNPs directly attached to the ITO (PdNP/ITO) electrode had a significantly lowered charge-transfer resistivity compared with that of a bare ITO, and the redox reaction of [Fe(CN)6]3-/[Fe(CN)6]4- was observed as reversible in 0.1 M phosphate buffer solution. The electrocatalytic property of PdNPs was confirmed for the reduction of oxygen. In addition, some typical responses were observed in 0.5 M H2SO4 with the PdNP/ITO electrode, reflecting both the characteristics of NPs and the thin layer in nanoscale. The present preparation method of PdNP-attached surfaces would be promising for catalytic applications as well as electrochemical uses.     

Preparation and Characterization of Bhant Leaves‐derived Nitrogen‐doped Carbon and its Use as an Electrocatalyst for Detecting Ketoconazole

In this study, the electrocatalytic characteristics of nitrogen‐doped carbon (NDC) prepared from Clerodendrum Infortunatum L leaves on a glassy carbon electrode (GCE) surface was evaluated with regards to its ability to detect the electroactive drug ketoconazole (KCZ). The NDC was prepared by carrying out a simple pyrolysis of dry powder of the leaves at 850 °C. The prepared NDC was characterized using field‐emission scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy and Brunauer‐Emmett‐Teller analysis, and was then used as an electrode material. The performance of the electrochemical KCZ sensor with the NDC‐modified glassy carbon electrode (NDC/GCE) was found to be optimal when using PBS buffer at pH 3 and a concentration of 0.1 mg/ml of NDC in the conjugate with Nafion polymer. Under these conditions, the NDC/GCE displayed a KCZ detection limit of 3 μM and a linear dependence of its response on KCZ concentration over a wide range of KCZ concentrations from 47 μM to 752 μM (R²=0.9742). These results confirmed the potential of NDC as an electrocatalyst.     

N-Doping of Polyaromatic Capsules: Small Cavity Modification Leads to Large Change in Host–Guest Interactions

To gain insight into the host functions of a nanocavity encircled by both polyaromatic panels and heteroatoms, nitrogen-doped polyaromatic capsules were successfully synthesized from metal ions and pyridine-embedded, bent anthracene-based ligands. The new capsules display unique host–guest interactions in the isolated cavities, which are distinct from those of the undoped analogues. Besides the inclusion of Ag⁺ ions, the large absorption change of fullerene C₆₀ and altered emission of a BODIPY dimer are observed upon encapsulation by the present hosts. Moreover, the N-doped capsule exhibits specific binding ability toward progesterone and methyltestosterone, known as a natural female and synthetic male hormone, respectively, in water.     

Alkylation‐, Heating‐, and Doping‐Induced Emission Enhancement of a Polyaromatic Tube in the Solid State

A polyaromatic tube with a subnanometer‐sized cavity was efficiently prepared on a gram‐scale through the stereo‐controlled cyclotrimerization of a diphenylanthracene derivative as a key step. The facile exterior alkylation of the polyaromatic framework leads to a moderately fluorescent tube (R=‐OC₁₀H₂₁; Φ_F=20 %) in the solid state. The emission intensity of the solid‐state alkyl‐substituted tube is remarkably enhanced upon heating (up to 1.6 times, Φ_F=31 %) as well as doping with fluorescent dyes (up to 4.2 times, Φ_F=83 %) through efficient energy transfer.