Unconventional Magnetic and Resistive Hysteresis in an Iodine-Bonded Molecular Conductor.

Simultaneous manipulation of both spin and charge is a crucial issue in magnetic conductors. We report on a strong correlation between magnetism and conductivity in the iodine-bonded molecular conductor (DIETSe)2 FeBr2 Cl2 [DIETSe=diiodo(ethylenedithio)tetraselenafulvalene], which is the first molecular conductor showing a large hysteresis in both magnetic moment and magnetoresistance associated with a spin-flop transition. Utilizing a mixed-anion approach and iodine bonding interactions, we tailored a molecular conductor with random exchange interactions exhibiting unforeseen physical properties.

Interlayer charge disproportionation in the layered organic superconductor κ(H)-(DMEDO-TSeF)2[Au(CN)4](THF) with polar dielectric insulating layers.

We report the molecular dipole effect on conduction electrons in the title superconductor. The angular-dependent magnetoresistance has a peak for fields nearly parallel to the conducting layer, and the peak width scales as the field component perpendicular to the layer, indicating incoherent interlayer transport. However, two closed Fermi surfaces are observed in quantum oscillation. Accordingly, crystallographically independent layers have different charge densities in a bulk single crystal. The electric dipole of tetrahydrofuran gives rise to interlayer charge disproportionation.

Spin-flop switching and memory in a molecular conductor.

We report the first observation of spin-flop-induced sharp positive magnetoresistance as large as 100% and nonvolatile magnetoresistive memory in a π-d hybrid molecular conductor, (DIETSe)(2)FeCl(4) [DIETSe = diiode(ethylenedithio)tetraselenafulvalene]. The unprecedented magnetotransport phenomena originate from the coexistence of the spin density wave (SDW) of the quasi-one-dimensional (Q1D) π electrons and the antiferromagnetic order of d-electron spins, indicating the interplay between the electronic instability of Q1D π electrons and local moments of antiferromagnetic d-electron spins. These findings offer new possibilities in molecular electronics/spintronics.

1H, 13C and 77Se NMR study of tetraselenafulvalene derivatives supported by novel H(Se)C and H(C)Se triple-resonance experiments at natural abundance.

A series of substituted tetraselenafulvalenes (TSeFs) was studied in solution using 1H, 13C and 77Se NMR spectroscopy. Chemical shifts and heteronuclear coupling constant values were determined and assigned. Novel two-dimensional H(Se)C and H(C)Se triple-resonance correlation experiments were applied at natural abundance in order to accomplish 13C and 77Se signal assignments. Using this approach, all the signals were unambiguously assigned and atom connectivity was established in the studied TSeF derivatives. These experiments, allowing signal assignments of quaternary carbons, may find wide application in the study of substituted TSeF and other organoselenium compounds. To the best of our knowledge, triple-resonance experiments with proton detection have been applied to organoselenium compounds for the first time.

Ambient-pressure organic superconductors kappa-(DMEDO-TSeF)2[Au(CN)4](solv.): Tc tuning by modification of the solvent of crystallization.

The unsymmetrical pi donor dimethyl(ethylenedioxy)tetraselenafulvalene (DMEDO-TSeF) has provided six new organic superconductors with a monovalent square-planar [Au(CN)(4)](-) ion and cyclic ethers as solvent of crystallization. The six new organic superconductors kappa-(DMEDO-TSeF)(2)[Au(CN)(4)](solv.) [solv.=1,3-dioxolane (DOL), 2,5-dihydrofuran (DHF), tetrahydropyran (THP), 1,3-dioxane (1,3-DOX), 3,4-dihydro-2H-pyran (DHP), or 1,4-dioxane (1,4-DOX)] are classified into two subphases kappa(L) and kappa' according to the differences in their space group symmetry. kappa(L)-(DMEDO-TSeF)(2)[Au(CN)(4)](solv.) (solv.=DOL, DHF, THP, 1,3-DOX or DHP) crystallizes in the orthorhombic space group Pnma, and T(c) of the kappa(L) phase varies by 1.7-5.3 K according to the size and shape of the solvent of crystallization. On the other hand, kappa'-(DMEDO-TSeF)(2)[Au(CN)(4)](solv.) (solv.=DOL or 1,4-DOX) crystallizes in the noncentrosymmetric monoclinic space group Cc. The kappa'-phase containing 1,4-DOX shows superconductivity at 4.2 K, but the kappa'-phase containing DOL does not show superconductivity down to 1.4 K. Systematic investigation of the six new organic superconductors, together with the two previously reported superconductors kappa(H)- and kappa(L)-(DMEDO-TSeF)(2)[Au(CN)(4)](THF), revealed that the T(c) of the present system is finely tunable by utilizing the effect of the solvent of crystallization.

New ambient pressure organic superconductors kappa H- and kappa L-(DMEDO-TSeF)2[Au(CN)4](THF).

We have developed two novel organic superconductors kappa H- and kappa L-(DMEDO-TSeF)2[Au(CN)4](THF) (DMEDO-TSeF = dimethyl(ethylenedioxy)tetraselenafulvalene) with the onset transition temperatures of 4.8 K for the kappa H-phase and 3.0 K for the kappa L-phase at ambient pressure, where DMEDO-TSeF is the second example following tetramethyltetraselenafulvalene (TMTSF) after an interval of 25 years as a sulfur-free donor providing a bulk organic superconductor.

A photoluminescent six-coordinated zinc(II) complex with hydroxides as axial ligands, [Zn(Hhpa)2(OH)2] (Hhpa = 3-hydroxypicolinamide).

A highly luminescent zinc(II) complex has been prepared using 3-hydroxypicolinamide; it has a six-coordinated octahedral structure with hydroxides as axial ligands in solution.

Synthesis, crystal structure and electrochemical properties of bis(ethylenedioxy)tetraselenafulvalene (BEDO-TSeF).

Bis(ethylenedioxy)tetraselenafulvalene (BEDO-TSeF) has been synthesized using elemental selenium as the only source of the selenium atoms, and its crystal structure and electrochemical properties are examined and compared with its sulfur analogues.

Synthesis of novel selenium-containing donors as selenium analogues of diiodo(ethylenedithio)diselenadithiafulvalene (DIETS).

Novel selenium analogues of diiodo(ethylenedithio)diselenadithiafulvalene (DIETS) have been successfully derived from 1,3-diselenole-2-thione, which could be synthesized without the use of the highly toxic reagent CSe(2).

Synthesis and properties of hetero-halogenated TTFs.

Novel hetero-halogenated TTFs containing both chlorine and iodine atoms were prepared and their unique characters based on the halogen atoms were examined.

CSe2-free synthesis of [1,3]diselenole-2-thione and its application to syntheses of iodinated tetraselenafulvalenes (TSeFs).

We developed a new CSe2-free protocol for the synthesis of [1,3]diselenole-2-thione and converted it to tetraselenafulvalene derivatives without any selenium-sulfur exchange side reactions.