Miwako Mori
Review: Recent Progress on Enyne Metathesis: Its Application to Syntheses of Natural Products and Related Compounds
Materials 2010, 3(3), 2087-2140; doi:10.3390/ma3032087 - published online 19 March 2010
Show/Hide AbstractAbstract: Olefin metathesis using ruthenium carbene complexes is a useful method in synthetic organic chemistry. Enyne metathesis is also catalyzed by these complexes and various carbo- and heterocycles could be synthesized from the corresponding enynes. Dienyne metathesis, cross enyne metathesis and ring-opening enyne metathesis have been further developed. Various complicated compounds, such as the natural products and the related biologically active substances, could be synthesized using these metatheses reactions. Skeletal reorganization using the transition metals and metallotropic rearrangement are also discussed.

Hooi Ling Lee, Issam Ahmed Mohammed, Mohammed Belmahi, Mohamed Badreddine Assouar, Hervé Rinnert and Marc Alnot
Article: Thermal and Optical Properties of CdS Nanoparticles in Thermotropic Liquid Crystal Monomers
Materials 2010, 3(3), 2069-2086; doi:10.3390/ma3032069 - published online 19 March 2010
Show/Hide AbstractAbstract: Two new mesogenic monomers, namely 3,3’-dimethoxy-4,4’-di(hydroxyhexoxy)-N-benzylidene-o-Tolidine (Ia) and 4,4’-di(6-hydroxyhexoxy)-N-benzylidene-o-Tolidine (IIa), were reacted with cadmium sulfide (CdS) via an in situ chemical precipitation method in ethanol to produce CdS nanocomposites. A series of different mass compositions of CdS with Ia and IIa ranging from 0.1:1.0 to 1.0:1.0 (w/w) were prepared and characterized using X-ray Diffraction (XRD), Raman spectroscopy, Fourier Transform Infrared Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM), Polarizing Optical Microscopy (POM) and Differential Scanning Calorimetry (DSC), X-ray Photoelectron Spectroscopy (XPS) and Photoluminescence Spectroscopy (PL). XRD showed that the broad peaks are ascribed to the formation of cubic CdS nanoparticles in both Ia and IIa. The average particle size for both nanocomposites was less than 5 nm with a narrower size distribution when compared with pure CdS nanoparticles. The analyses from POM and DSC demonstrated that mass composition from 0.1:1.0 up to 0.5:1.0 of CdS:Ia nanocomposites showed their enantiotropic nematic phase. On the other hand, polarizing optical microscopy (POM) for IIa nanocomposites showed that the liquid crystal property vanished completely when the mass composition was at 0.2:1.0. PL emissions for CdS: Ia or IIa nanocomposites indicated deep trap defects occurred in these both samples. The PL results revealed that addition of CdS to Ia monomers suppressed the photoluminescence intensity of Ia. However, the introduction of CdS to IIa monomers increased the photoluminescence and was at a maximum when the mass composition was 0.3:1.0, then decreased in intensity as more CdS was added. The XPS results also showed that the stoichiometric ratios of S/Cd were close to 1.0:1.0 for both types of nanocomposites for a mass composition of 1.0:1.0 (CdS:matrix).

Luiz G. Jacobsohn, Courtney J. Kucera, Tiffany L. James, Kevin B. Sprinkle, Jeffrey R. DiMaio, Baris Kokuoz, Basak Yazgan-Kukouz, Timothy A. DeVol and John Ballato
Review: Preparation and Characterization of Rare Earth Doped Fluoride Nanoparticles
Materials 2010, 3(3), 2053-2068; doi:10.3390/ma3032053 - published online 19 March 2010
Show/Hide AbstractAbstract: This paper reviews the synthesis, structure and applications of metal fluoride nanoparticles, with particular focus on rare earth (RE) doped fluoride nanoparticles obtained by our research group. Nanoparticles were produced by precipitation methods using the ligand ammonium di-n-octadecyldithiophosphate (ADDP) that allows the growth of shells around a core particle while simultaneously avoiding particle aggregation. Nanoparticles were characterized on their structure, morphology, and luminescent properties. We discuss the synthesis, properties, and application of heavy metal fluorides; specifically LaF₃:RE and PbF₂, and group IIA fluorides. Particular attention is given to the synthesis of core/shell nanoparticles, including selectively RE-doped LaF₃/LaF₃, and CaF₂/CaF₂ core/(multi-)shell nanoparticles, and the CaF₂-LaF₃ system.

Tohru Nishinaga, Daisuke Yamazaki, Masaki Tateno, Masahiko Iyoda and Koichi Komatsu
Article: Synthesis and Properties of Octithiophene Dication Sterically Segregated by Annelation with Bicyclo[2.2.2]octene Units
Materials 2010, 3(3), 2037-2052; doi:10.3390/ma3032037 - published online 19 March 2010
Show/Hide AbstractAbstract: Octithiophene sterically segregated by annelation with bicyclo[2.2.2]octene (BCO) units was synthesized to study the unimolecular properties of longer oligothiophene dications. For the preparation of such longer oligomers, a new route for the synthesis of the monomer annelated with BCO unit at the 3,4-positions of thiophene ring was developed. Attempted synthesis of octithiophene 1(8T) fully annelated with BCO units was hampered by low solubility of the product, and octithiophene 2(8T) having octyl groups instead of the BCO units at the second rings from the both ends of 1(8T) was synthesized to solve the solubility problem. Neutral 2(8T) has a lower planarity due to the steric repulsion between the octyl substituents and the neighboring thiophene units. However, dication 2(8T)²⁺, which was obtained as a stable salt by chemical two-electron oxidation with NO⁺SbF₆^-, has a planar quinoid structure, as judged from a linear correlation between the inverse chain length and the absorption energy for 1(nT)²⁺ (n = 3,4,6) and 2(8T)²⁺. Based on the comparison with the calculated absorption spectra and the result of ESR inactive properties, 2(8T)²⁺ appears to have a singlet ground state with open-shell biradical character rather than a closed-shell singlet structure.

Tomohiro Suko, Ichiro Terasaki, Hatsumi Mori and Takehiko Mori
Article: A Mechanism of DC-AC Conversion in the Organic Thyristor
Materials 2010, 3(3), 2027-2036; doi:10.3390/ma3032027 - published online 19 March 2010
Show/Hide AbstractAbstract: The charge ordered organic salt θ-(BEDT-TTF)₂CsZn(SCN)₄ exhibits a giant nonlinear conduction at low temperatures. The voltage-current characteristics of this compound are similar to those of a thyristor device, after which we named it the organic thyristor. This material shows current oscillation in the presense of dc voltage, which arises from a mechanism different from conventional oscillating circuits, because the oscillation appears in a sample that does not show negative derivative resistance. We have performed a standard circuit analysis, and show that the voltage-current curve is “blurred” in the high current region, and the oscillation occurs in the blurred region. This type of oscillation has never been reported, and a possible origin for this is suggested.

Demetra S. Achilleos and Maria Vamvakaki
Review: End-Grafted Polymer Chains onto Inorganic Nano-Objects
Materials 2010, 3(3), 1981-2026; doi:10.3390/ma3031981 - published online 18 March 2010
Show/Hide AbstractAbstract: Organic/inorganic nanohybrid materials have attracted particular scientific and technological interest because they combine the properties of the organic and the inorganic component. Inorganic nanoparticles exhibit interesting electrical, optical, magnetic and/or catalytic properties, which are related with their nano-scale dimensions. However, their high surface-to-volume ratio often induces agglomeration and leads to the loss of their attractive properties. Surface modification of the inorganic nano-objects with physically or chemically end-tethered polymer chains has been employed to overcome this problem. Covalent tethered polymer chains are realized by three different approaches: the “grafting to”, the “grafting from” and the “grafting through” method. This article reviews the synthesis of end-grafted polymer chains onto inorganic nanoparticles using “controlled/living” polymerization techniques, which allow control over the polymer characteristics and the grafting density of the end-tethered polymer chains.