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1.
Org Lett ; 13(12): 3285-7, 2011 Jun 17.
Article in English | MEDLINE | ID: mdl-21604776

ABSTRACT

The regio- and stereoselective addition of carboxylic acids to aryl and trifluoromethyl group substituted unsymmetrical internal alkynes has been accomplished: the Ru(3)(CO)(12)/3PPh(3) catalyst system has effectively catalyzed the reaction to afford the trifluoromethyl group substituted (E)-enol esters with high regio- and stereoselectivities.

2.
Org Lett ; 13(5): 1001-3, 2011 Mar 04.
Article in English | MEDLINE | ID: mdl-21288010

ABSTRACT

It found that the Ru(3)(CO)(12) coordinated with 2-(diphenylphosphino)benzonitrile (2-DPPBN) to effectively catalyze the [2 + 2 + 2] cyclotrimerization of the trifluoromethyl group substituted internal alkynes in high yields with up to >98% regioselectivity. Isolation of a ruthenacyclopentadiene was successful and confirmed that the complex is a reaction intermediate.


Subject(s)
Alkynes/chemistry , Fluorobenzenes/chemical synthesis , Hydrocarbons, Fluorinated/chemistry , Hydrocarbons, Fluorinated/chemical synthesis , Nitriles/chemistry , Phosphines/chemistry , Ruthenium/chemistry , Catalysis , Crystallography, X-Ray , Cyclization , Fluorobenzenes/chemistry , Molecular Structure , Stereoisomerism
3.
Phys Rev Lett ; 102(17): 176403, 2009 May 01.
Article in English | MEDLINE | ID: mdl-19518803

ABSTRACT

We report on the experimental results of interlayer magnetoresistance in the multilayer massless Dirac fermion system alpha-(BEDT-TTF)2I3 under hydrostatic pressure and its interpretation. We succeeded in detecting the zero-mode Landau level (n=0 Landau level) that is expected to appear at the contact points of Dirac cones in the magnetic field normal to the two-dimensional plane. The characteristic feature of zero-mode Landau carriers including the Zeeman effect is clearly seen in the interlayer magnetoresistance.

4.
Sci Technol Adv Mater ; 10(2): 024308, 2009 Apr.
Article in English | MEDLINE | ID: mdl-27877281

ABSTRACT

A zero-gap state with a Dirac cone type energy dispersion was discovered in the organic conductor α-(BEDT-TTF)2I3 under high hydrostatic pressures. This is the first two-dimensional (2D) zero-gap state discovered in bulk crystals with a layered structure. In contrast to the case of graphene, the Dirac cone in this system is highly anisotropic. The present system, therefore, provides a new type of massless Dirac fermion system with anisotropic Fermi velocity. This system exhibits remarkable transport phenomena characteristic to electrons on the Dirac cone type energy structure. The carrier density, written as n∝T2, is a characteristic feature of the 2D zero-gap structure. On the other hand, the resistivity per layer (sheet resistance RS) is given as RS=h/e2 and is independent of temperature. The effect of a magnetic field on samples in the zero-gap system was examined. The difference between zero-gap conductors and conventional conductors is the appearance of a Landau level called the zero mode at the contact points when a magnetic field is applied normal to the conductive layer. Zero-mode Landau carriers give rise to strong negative out-of-plane magnetoresistance.

5.
Chemistry ; 13(6): 1872-81, 2007.
Article in English | MEDLINE | ID: mdl-17136783

ABSTRACT

The crystal architecture, magnetic properties, and thermodynamic properties of [n-butylferrocene][Ni(mnt)2] (1), [tert-butylferrocene][Ni(mnt)2] (2), [1,1'-diethylferrocene][Ni(mnt)2] (3), and [1,1'-diisopropylferrocene][Ni(mnt)2] (4) were investigated (mnt=maleonitriledithiolate). These complexes exhibit a unique supramolecular structure in which the ferrocenium cations constitute honeycomb-like assembled structures surrounding columns of the anions. For 1, the cations form a dimer through a very short intermolecular ferrocene-ferrocene distance of 3.28 A, which mediates an antiferromagnetic interaction with a singlet-triplet energy gap of 5 K. First-order phase transitions occur in 1-3 at 364, 361, and 350 K, respectively, accompanied by thermal hysteresis.

6.
Inorg Chem ; 44(23): 8628-41, 2005 Nov 14.
Article in English | MEDLINE | ID: mdl-16271005

ABSTRACT

Charge-transfer salts of branched-alkyl biferrocenes, (1',1' ''-R2-1,1' '-biferrocene)[Ni(mnt)2] (1a, R = isopropyl; 2a, R = dineopentyl) and (1',1' ''-R2-1,1' '-biferrocene)2[Co(mnt)2]2 (1b, R = isopropyl; 2b, R = dineopentyl), were prepared. Their valence states were investigated using X-ray crystallography and Mössbauer spectroscopy. Complexes 1a and 1b show segregated-stack crystal structures that contain columns of acceptors, whereas structures of 2a and 2b, which contain bulky donors, are rather discrete. All of the complexes contain mixed-valent biferrocenium monocations. A two-step valence transition was found in complex 1a. The crystal contains two crystallographically independent cations: one undergoes valence localization below room temperature; the other undergoes valence localization below ca. 130 K. The former transition is derived from asymmetry of the crystal environment around the cation, whereas the latter one is caused by symmetry lowering coupled with a spin-Peierls transition (T(C) = 133.2 K) associated with the dimerization of the acceptors. This compound was found to exhibit a dielectric response based on valence tautomerization. Other complexes (1b, 2a, and 2b) show a valence-trapped state. In all complexes, charge localization was found to occur through local electrostatic interactions between the donor's cationic moiety and the acceptor's electronegative moieties.

7.
Chem Commun (Camb) ; (21): 2454-5, 2004 Nov 07.
Article in English | MEDLINE | ID: mdl-15514812

ABSTRACT

A newly synthesized donor meso-DMBEDT-TTF [DMBEDT-TTF = 2-(5,6-dihydro-1,3-dithiolo[4,5-b][1,4]dithiin-2-ylidene)-5,6-dihydro-5,6-dimethyl-1,3-dithiolo[4,5-b][1,4]dithiin] afforded a superconducting salt beta-(meso-DMBEDT-TTF)2PF6, with a transition temperature at 4.3 K (onset) under a hydrostatic pressure of 4.0 kbar.


Subject(s)
Electric Conductivity , Heterocyclic Compounds, 2-Ring/chemistry , Sulfhydryl Compounds/chemistry , Crystallography, X-Ray , Models, Molecular , Molecular Structure , Temperature
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