Search for new iron oxypnictide superconductors by using high-pressure synthesis technique

Here we report on the invention of the Co-doped induced superconductivity in PrFe_1−xCo_xAsO (x = 0 and 0.075). Polycrystalline samples were prepared by high-pressure synthesis method. The PrFe_1−xCo_xAsO (x = 0 and 0.075) crystallizes with the ZrCuSiAs type crystal structure (P4/nmm). The PrFeAsO is a parent compound with non-superconducting phase which can be transformed to superconductor by replacement 7.5% of Fe by Co. The magnetic susceptibility measurement shows the onset of superconducting transition temperature at 15 K.     

Synthesis and structure of new water-soluble and stable tantalum compound: ammonium tetralactatodiperoxo-mu-oxo-ditantalate(V)

The stable water-soluble tantalum complex with lactic acid (ammonium tetralactatodiperoxo-mu-oxo-ditantalate(V)), (NH4)4[Ta2(C3H4O3)4(O2)2O].3H2O, was prepared in the crystalline form. According to the single-crystal X-ray diffraction data, this compound forms a monoclinic cell with a = 13.85(2) A, b = 9.06(1) A, c = 12.32(2) A, and beta = 116.30 degrees , space group C2 (No. 2), and has Z = 2 molecules per unit cell. The solid-state 13C NMR data and low flack parameter are consistent with the determined structure. Appearance of the same vibration modes in Raman and IR spectra supports the choice of the space group without inversion symmetry. The solution of the tantalum complex was successfully applied for the synthesis of two photocatalytic materials, NaTaO3 and Sr2Ta2O7.     

Ring expansion of isopropenyldihydrofuran derivatives

Lactonization of 2‐(hydroxymethyl)‐5‐isopropenyl‐4,5‐dihydrofuran‐3‐carboxylic acids 1a,b,c with dicyclohexylcarbodiimide gave the corresponding furano‐lactones, 5‐isopropenyl‐5,6‐dihydro‐1(3H)‐furo[3,4‐b]furanone 2a,b,c , which were readily converted to the corresponding oxepino‐lactones, 6‐methyl‐5,8‐dihydro‐1(3H)‐furo[3,4‐b]oxepinone 3a,b,c by respective thermal ring expansions.     

Simultaneous observation of CO isotopomer absorption by broadband difference-frequency generation using a direct-bonded quasi-phase-matched LiNbO3 waveguide

Rovibration absorption lines both of 12CO and 13CO are observed simultaneously with the output of a 2 microm broadband difference frequency generated in a direct-bonded quasi-phase-matched LiNbO3 waveguide, which is a 50 mm device with a single quasi-phase-matching period that is operated at a constant temperature. The wavelength conversion efficiency and the difference-frequency generation bandwidth reach 100%/W and 100 nm, respectively. The idler output bandwidth in the 2 microm region is obtained by group-velocity matching or phase-mismatch minimization when a 0.94 microm pump laser diode and a 1.55 microm tunable signal source are used.     

Organometallic Rotaxanes with a Triazole Group in the Axle Component and Their Behavior as Ligands of PtII Complexes

Two ferrocenylmethyl ammonium salts were used as axle components of pseudorotaxanes with dibenzo[24]crown‐8. The pseudorotaxane with an alkyne terminal group in the axle component underwent a Cu‐catalyzed Huisgen coupling reaction (click reaction) with an alkyl azide to afford cationic [2]rotaxanes with a triazole group in the axle molecule. The rotaxane reacted with Ac₂O to produce neutral rotaxanes with an amide group in the axle component. Both cationic and neutral rotaxanes were treated with K[PtCl₃(CH₂?CH₂)] to form the Pt^II‐containing rotaxanes.     

Columnar self-assembly of rhomboid macrocyclic molecules via step-like intermolecular interaction. Crystal formation and gelation

Two macrocyclic compounds with a rhomboid molecular shape, composed of a π-conjugated framework and an imine or amine functionality, were synthesized. The amine-containing macrocycle crystallizes with step-like interaction of each molecule, forming a columnar arrangement, although dispersion of the imine gelates upon ultrasonification.     

Reaction of an alkyne with dinickel-diphenylsilyl complexes. An emissive disilane formed via the consecutive Si-C and Si-Si bond-making processes

[{Ni(dmpe)}(2)(μ-SiHPh(2))(2)] (dmpe = 1,2-bis(dimethylphosphino)ethane) reacted with PhC≡CPh to yield fluorescent 1,2-bis{(E)-1,2-diphenylethenyl}-1,1,2,2-tetraphenyldisilane via addition of the Si-H bond of the ligand to the alkyne and subsequent coupling of the tertiary silyl ligands forming the Si-Si bond.     

Superconducting fullerene nanowhiskers

We synthesized superconducting fullerene nanowhiskers (C(60)NWs) by potassium (K) intercalation. They showed large superconducting volume fractions, as high as 80%. The superconducting transition temperature at 17 K was independent of the K content (x) in the range between 1.6 and 6.0 in K-doped C(60) nanowhiskers (K(x)C(60)NWs), while the superconducting volume fractions changed with x. The highest shielding fraction of a full shielding volume was observed in the material of K(3.3)C(60)NW by heating at 200 °C. On the other hand, that of a K-doped fullerene (K-C(60)) crystal was less than 1%. We report the superconducting behaviors of our newly synthesized K(x)C(60)NWs in comparison to those of K(x)C(60) crystals, which show superconductivity at 19 K in K(3)C(60). The lattice structures are also discussed, based on the x-ray diffraction (XRD) analyses.     

Ultrafast optical signal measurementusing optoelectronic techniques

Optical and Quantum Electronics - A novel ultrafast optical signal measurement technique is proposed that uses a fast photodetector and electrooptic (EO) sampling. The technique can satisfy three...