Enantiomorphic single component conducting nickel(II) and platinum(II) bis(diethyl-dddt) crystalline complexes.

Monoanionic and neutral nickel(II) and platinum(II) bis(dithiolene) complexes based on the 5,6-diethyl-5,6-dihydro-1,4-dithiin-2,3-dithiolate (de-dddt) chiral ligand have been prepared in racemic and enantiopure forms. Neutral closed-shell species have been generated from monoanionic precursors upon electrocrystallization. The racemic anionic (TBA)[Ni(,-de-dddt)(,-de-dddt)] complex crystallized in the centrosymmetric space group 2/, while the neutral complexes crystallized in the enantiomorphic tetragonal space group 422 or 422.

Mixed-Valence Conductors from Ni Bis(diselenolene) Complexes with a Thiazoline Backbone.

Highly conducting, mixed-valence, multi-component nickel bis() salts were obtained by electrocrystallization of the monoanionic species [Ni(Me-thiazds)] (Me-thiazds: -methyl-1,3-thiazoline-2-thione-4,5-diselenolate), with 1:2 and 1:3 stoichiometries depending of the counter ion used (EtN and BuN PhP, respectively). This behavior strongly differs from that of the corresponding monoanionic complexes whose oxidation afforded the single component neutral species. This provides additional rare examples of mixed-valence conducting salts of nickel diselenolene complexes, only known in two examples with the dsit (1,3-dithiole-2-thione-4,5-diselenolate) and dsise (1,3-dithiole-2-selone-4,5-diselenolate) ligands.

Introducing Selenium in Single-Component Molecular Conductors Based on Nickel Bis(dithiolene) Complexes.

Two selenated analogues of the all-sulfur single-component molecular conductor [Ni(Et-thiazdt)] (Et-thiazdt = -ethylthiazoline-2-thione-4,5-dithiolate) have been prepared from their precursor radical-anion complexes. Replacement of the thione by a selenone moiety gives the neutral [Ni(Et-thiazdt)] complex. It adopts an unprecedented solid-state organization (for neutral nickel complexes), with the formation of perfectly eclipsed dimers and very short intermolecular Se···Se contacts (81% of the van der Waals contact distance).

Role of the Open-Shell Character on the Pressure-Induced Conductivity of an Organic Donor-Acceptor Radical Dyad.

Single-component conductors based on neutral organic radicals have received a lot of attention due to the possibility that the unpaired electron can serve as a charge carrier without the need of a previous doping process. Although most of these systems are based on delocalized planar radicals, we present here a nonplanar and spin localized radical based on a tetrathiafulvalene (TTF) moiety, linked to a perchlorotriphenylmethyl (PTM) radical by a conjugated bridge, which exhibits a semiconducting behavior upon application of high pressure. The synthesis, electronic properties, and crystal structure of this neutral radical TTF-Ph-PTM derivative (1) are reported and implications of its crystalline structure on its electrical properties are discussed.

Emergence of the Dirac Electron System in a Single-Component Molecular Conductor under High Pressure.

Single-component molecular conductors can provide a variety of electronic states. We demonstrate here that the Dirac electron system emerges in a single-component molecular conductor under high pressure. First-principles density functional theory calculations revealed that Dirac cones are formed in the single-component molecular conductor [Pd(dddt)] (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate), which shows temperature-independent resistivity (zero-gap behavior) at 12.

Pressure-Induced Conductivity in a Neutral Nonplanar Spin-Localized Radical.

There is a growing interest in the development of single-component molecular conductors based on neutral organic radicals that are mainly formed by delocalized planar radicals, such as phenalenyl or thiazolyl radicals. However, there are no examples of systems based on nonplanar and spin-localized C-centered radicals exhibiting electrical conductivity due to their large Coulomb energy (U) repulsion and narrow electronic bandwidth (W) that give rise to a Mott insulator behavior. Here we present a new type of nonplanar neutral radical conductor attained by linking a tetrathiafulvalene (TTF) donor unit to a neutral polychlorotriphenylmethyl radical (PTM) with the important feature that the TTF unit enhances the overlap between the radical molecules as a consequence of short intermolecular S···S interactions.

A single-component molecular superconductor.

The pressure dependence of the resistivities of a single-component molecular conductor, [Ni(hfdt)2] (hfdt = bis(trifluoromethyl)tetrathiafulvalenedithiolate) with semiconducting properties at ambient pressure was examined. The four-probe resistivity measurements were performed up to ∼10 GPa using a diamond anvil cell. The low-temperature insulating phase was suppressed above 7.

Lattice distortion stabilizes the photoinduced metallic phase in the charge-ordered organic salts (BEDT-TTF)3X2 (X=ReO4, ClO4).

Photoinduced effects caused by intramolecular excitation were investigated by simultaneous optical and transport measurement in two charge-ordered organic salts, (BEDT-TTF)3X2 (X=ReO4, ClO4) [BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene]. Although the two salts have the same molecular (average) charge and arrangement, they showed different photoinduced effects. A photoinduced insulator-to-metal phase transition with a metastable charge order-melting state was observed in the ReO4 salt where the charge ordered state is associated with the lattice distortion.

Single-component molecular conductor [Cu(dmdt)2] with three-dimensionally arranged magnetic moments exhibiting a coupled electric and magnetic transition.

Crystals of the single-component molecular conductor [Cu(dmdt)(2)] (dmdt = dimethyltetrathiafulvalenedithiolate) were prepared as a molecular system, with three-dimensionally arranged magnetic moments embedded in "sea" of π conduction electrons. [Cu(dmdt)(2)] had fairly large room-temperature conductivity (110 S cm(-1)) and exhibited weakly metallic behavior near room temperature. Below 265 K, the resistivity (R) increased very slowly with decreasing temperature and then increased rapidly, indicating a transition from a highly conducting state to an insulating state near 95 K.

Anomalous dielectric behavior and thermal motion of water molecules confined in channels of porous coordination polymer crystals.

Guest water molecules confined in channels of porous coordination polymer crystals [Ln(2)Cu(3)(IDA)(6)]·nH(2)O (Ln = La, Nd, Sm, Gd, Ho, Er; IDA = [NH(CH(2)COO)(2)](2-); n ≈ 9) exhibited large dielectric constants (ε) and antiferroelectric behaviors at high temperatures (e.g., ε(Sm) ≈ 1300 at 400 K).

Evidence of the chemical uniaxial strain effect on electrical conductivity in the spin-crossover conducting molecular system: [Fe(III)(qnal)2][Pd(dmit)2]5.acetone.

A novel spin-crossover molecular conductor, [Fe(qnal)2][Pd(dmit)2]5.acetone, was prepared and characterized. The crystal structural analyses of both the low- and high-temperature phases revealed that the supramolecular pi-pi interactions between the spin-crossover Fe(qnal)2 cations as well as the cation contraction play an important role in the uniaxial lattice deformation which will modulate the electrical conductivity of the conducting Pd(dmit)2 layer.

Electrical resistivity of tetramethyltetratelluronaphtalene crystal at very high pressures - examination of the condition of metallization of pi molecular crystal.

Four-probe resistivity measurements were performed on the TMTTeN crystal by using a diamond anvil high-pressure cell up to 30 GPa. The crystal could not be metallized though the room-temperature resistivity decreased to a very small value (1.5 x 10-3 Omega cm).

Ferroelectric porous molecular crystal, [Mn3(HCOO)6](C2H5OH), exhibiting ferrimagnetic transition.

A porous molecular crystal with guest ethanol molecules, [Mn3(HCOO)6](C2H5OH), was found to be a new type of multifunctional molecular system, which exhibits a ferroelectric transition at 165 K and a ferrimagnetic transition at 8.5 K. [Mn3(HCOO)6](C2H5OH) will give a hint to design "multiferroic" molecular materials where ferroelectric and ferromagnetic orders coexist.

Electrical conductivity modulation coupled to a high-spin-low-spin conversion in the molecular system [FeIII(qsal)2][Ni(dmit)2]3.CH3CN.H2O.

The synergy between the electrical conductivity within the stacks of Ni(dmit)2 in the newly electrocrystallized [Fe(qsal)2][Ni(dmit)2]3.CH3CN.H2O and the spin conversion of Fe(qsal)2 is evidenced.