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 7.5 GPa and the resistivity dropped, indicating the superconducting transition occurred around 7.5-8.7 GPa with a maximum Tc (onset temperature) of 5.5 K. The high-pressure crystal and electronic band structures were derived by the first-principle calculations at 6-11 GPa. The crystal was found to retain the semiconducting band structure up to 6 GPa. But the electron and hole Fermi surfaces appear at 8 GPa. These results of the calculations agree well with the observation that the pressure-induced superconducting phase of [Ni(hfdt)2] appeared just above the critical pressure where the low-temperature insulating phase was suppressed.

The vomeronasal organ and incisive duct of harbor seals are modified to secrete acidic mucus into the nasal cavity.

Most terrestrial mammals have a vomeronasal system to detect specific chemicals. The peripheral organ of this system is a vomeronasal organ (VNO) opening to the incisive duct, and its primary integrative center is an accessory olfactory bulb (AOB). The VNO in seals is thought to be degenerated like whales and manatees, unlike otariids, because of the absence of the AOB. However, olfaction plays pivotal roles in seals, and thus we conducted a detailed morphological evaluation of the vomeronasal system of three harbor seals (Phoca vitulina). The VNO lumen was not found, and the incisive duct did not open into the oral cavity but was recognized as a fossa on the anteroventral side of the nasal cavity. This fossa is rich in mucous glands that secrete acidic mucopolysaccharides, which might originate from the vomeronasal glands. The olfactory bulb consisted only of a main olfactory bulb that received projections from the olfactory mucosa, but an AOB region was not evident. These findings clarified that harbor seals do not have a VNO to detect some chemicals, but the corresponding region is a specialized secretory organ.

Molecular alloy with diluted magnetic moments-molecular Kondo system.

[Ni(1-x)Cu(x)(tmdt)(2)] (tmdt = trimethylenetetrathiafulvalenedithiolate) was prepared for realizing molecular Kondo systems. Magnetic moments (S = (1)/(2)) are considered to exist at the central {CuS(4)} parts of Cu(tmdt)(2) molecules. The χT-versus-T curve of the system with x ≈ 0.15 showed a broad peak at ~10 K. The decrease in the χT value below 10 K is consistent with a singlet ground state, as expected for a Kondo system. However, in the system with x ≈ 0.27, the χT value decreased when the temperature was lowered to 2 K, indicating antiferromagnetic interactions between magnetic moments through π-d interactions. Although the susceptibility anomaly suggested that the π-d interactions become important at T < 20 K, the observed resistivity (ρ(obs)) showed no resistivity minimum characteristic of a Kondo system down to 4.2 K. However, the differential resistivity Δρ(T) = ρ(obs) - ρ(L)(T) showed a logarithmic resistivity increase at 8-20 K with decreasing temperature, where ρ(L)(T) is a fitted function of ρ(obs) obtained at T > 50 K that is considered to represent approximately the temperature dependence of the resistivity without spin scattering of the conduction electrons.

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. The magnetic susceptibility showed Curie-Weiss behavior at 100-300 K (C = 0.375 emu/mol, Θ = 180 K). The Curie constant and the high-temperature resistivity behavior indicate that conduction electrons and three-dimensionally arranged magnetic moments coexist in the crystal. The ESR intensity increased down to about 95 K. The ESR signal was broadened and decreased abruptly near 95 K, suggesting that electric and antiferromagnetic transitions occurred simultaneously near 95 K. The crystal structure was determined down to 13 K. To examine the stability of the twisted conformation of Cu complex with dithiolate ligands, the dihedral angle dependence of the conformational energy of an isolated M(L)(2)(n-) molecule was calculated, which revealed the dihedral angle dependence on the ligand (L) and the oxidation state of the molecule (n). High-pressure four-probe resistivity measurements were performed at 3.3-9.3 GPa using a diamond anvil cell. The small resistivity increase observed at 3.3 GPa below 60 K suggested that the insulating transition observed at ambient pressure near 95 K was essentially suppressed at 3.3 GPa. The intermolecular magnetic interactions were examined on the basis of simple mean field theory of antiferromagnetic transition and the calculated intermolecular overlap integrals of the singly occupied molecular orbital (SOMO) of Cu(dmdt)(2).

Charge ordering and carrier generation by air oxidation of a nickel complex with selenium-containing extended-tetrathiafulvalenedithiolate ligands.

The structures and electrical properties of ((n)Bu(4)N)[Ni(dmstfdt)(2)] (1), ((n)Bu(4)N)(2)[Ni(dmstfdt)(2)] (2), and ((n)Bu(4)N)(3)[Ni(dmstfdt)(2)](2) (3), where dmstfdt = extended-tetrathiafulvalenedithiolate ligand, were examined. The fresh crystal of 1 was found to be a Mott insulator, but the crystal gradually became highly conducting because of air oxidation. Compound 3 exhibited a semiconducting charge-ordering state.

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). In addition, plots of the temperature dependence of ε showed broad peaks at ∼170 K, below which ε became very small. These puzzling temperature dependences of ε are consistent with the results of molecular dynamics simulations, suggesting the "freezing of thermal motion" of water molecules at ∼170 K.

Population-level laterality in foraging finless porpoises.

Laterality has been reported in many vertebrates, and asymmetrical cerebral hemisphere function has been hypothesized to cause a left-bias in social behavior and a right-bias in feeding behavior. In this paper, we provide the first report of behavioral laterality in free-ranging finless porpoises, which seems to support the aforementioned hypothesis. We observed the turning behavior of finless porpoises in Omura Bay, Japan, using land-based and unmanned aerial system observations. We found a strong tendency in finless porpoises to turn counterclockwise with their right side down when pursuing and catching fish at the surface of the water. Our results suggest that this population of finless porpoises shows consistent right-biased laterality. Right-biased laterality has been observed in various foraging cetaceans and is usually explained by the dominance of the right eye-left cerebral hemisphere in prey recognition; however, right-biased laterality in foraging cetaceans may have multiple causes.

Single-component molecular conductor [Cu(tmdt)(2)] containing an antiferromagnetic Heisenberg chain.

Traditional molecular conductors are composed of more than two chemical species and are characterized by low-dimensional electronic band structures. By contrast, the single-component molecular metals [M(tmdt)(2)] (M = Ni, Pt, Au; tmdt = trimethylenetetrathiafulvalenedithiolate) possess three-dimensional electronic structures that can be widely tuned by exchanging the central transition metal atom (M). In this study, the Cu atom was used to realize a new magnetic single-component molecular conductor exhibiting strong pi-d interactions. The crystal structure of [Cu(tmdt)(2)] was found to be essentially the same as those of the Ni, Pt, or Au-based systems with metallic states down to low temperature, but different from the structure of [Cu(dmdt)(2)] (dmdt = dimethyltetrathiafulvalenedithiolate) with its tetrahedrally coordinated dmdt ligands. A compressed pellet of microcrystals exhibited fairly high room-temperature conductivity (sigma(RT) approximately 7 S.cm(-1)), which increased almost linearly with pressure, reaching 110 S.cm(-1) at 15 kbar. This strongly suggests that the single crystal of [Cu(tmdt)(2)] is metallic at high pressure. Magnetic susceptibility measurements indicated one-dimensional Heisenberg behavior with |J| = 117 cm(-1) and an antiferromagnetic transition at 13 K. Density functional theory molecular orbital calculations revealed that the alpha-spin orbital of pdsigma(-) is distributed at the central part of the complex (CuS(4)), and alpha- and beta-sym-Lpi orbitals have almost the same energies and their spins are distributed mainly in the pdsigma(-) orbital. This is in contrast to the first single-component molecular metal [Ni(tmdt)(2)], which has stable metal bands formed from an almost degenerated sym-Lpi orbital (the highest occupied molecular orbital) and asym-Lpi(d) orbital (the lowest unoccupied molecular orbital). These results suggest that the alpha-pdsigma(-) state of [Cu(tmdt)(2)] exists just around the Fermi energy of the virtual metal band formed from the asym-Lpi(d) and sym-Lpi states. Thus, as expected, [Cu(tmdt)(2)] is a non-trivial single-component molecular conductor with pi-d multifrontier orbitals. In addition, ((n)Bu(4)N)(2)[Cu(tmdt)(2)] was synthesized, and its crystal structure was determined. Its Curie behavior (chi(rt) = 1.2 x 10(-3) emu mol(-1); C = 0.36 emu.K mol(-1)) indicates the existence of an isolated S = 1/2 spin on each dianionic molecule.

Long-term associations among male sperm whales (Physeter macrocephalus).

Little is known about the social structure of male sperm whales (Physeter macrocephalus) after they leave their natal units. While previous studies found no evidence for preferred associations among males, the observation of mass-strandings consisting exclusively of males, suggest that they have strong social bonds. To investigate the social associations among male sperm whales, we used half weight index of association, permutation tests and standardized lagged association rate models on a large photo-identification database collected between 2006 and 2017 in Nemuro Strait, Japan. Our results suggest that while male sperm whales are not as social as females, they do form long term associations, have preferred companionship, and forage in social proximity to each other. The best-fitting model to the standardized lagged association rate showed that associations among males last for at least 2.7 years and as most males leave the area after 2 years, associations may last for longer. Twenty dyads were observed associating over more than 2 years, for a maximum 5 years. One dyad was observed associating on 19 different days and clustered on 7 different days. Male associations may function to enhance foraging or to fend off predators. Such relationships seem to be adapted to a pelagic habitat with uncertain resource availability and predation pressure.

Metallization of the single component molecular semiconductor [Ni(ptdt)2] under very high pressure.

The four-probe electrical resistivity measurements on a single-component molecular semiconductor [Ni(ptdt)(2)] (Ni(S(8)C(9)H(6))(2)) was performed up to 20.7 GPa by using a diamond anvil cell. A newly improved method was employed to reduce the effect of uniaxial pressure. The semiconducting behavior persisted up to 17.9 GPa. The pressure-induced metallization began to appear at 18.9 GPa, and the complete metallic behavior down to 1 K was observed at 19.9 GPa.

High-pressure (up to 10.7 GPa) crystal structure of single-component molecular metal [Au(tmdt)2].

The crystal structure of the single-component molecular metal [Au(tmdt)(2)] was examined at pressures up to 10.7 GPa in order to examine whether the high-pressure structure reflects the crystal's metallic nature. Crystal structure analyses were performed at 0.2, 0.8, 1.3, 3.0, 5.5, and 10.7 GPa on the basis of the powder X-ray diffraction data obtained by using the synchrotron radiation source SPring-8. The unit cell volume at 10.7 GPa was approximately 75% of the initial volume, indicating that [Au(tmdt)(2)] is a 'soft material' like a typical molecular crystal in spite of its metallic nature. The pressure dependences of the bond lengths of the Au(tmdt)(2) molecule were found to be approximately 1 order of magnitude smaller than those of the intermolecular atomic distances. These results seem to justify the commonly accepted conjecture that the molecule usually behaves almost like a rigid body up to a fairly high pressure. It was found that the anisotropy of the lattice compression of the insulating I(2) crystal below 20 GPa can be essentially interpreted on the basis of a very simple 'interatomic repulsion model', which assumes that the molecules in the crystal are packed such that as far as possible, an increase in the interatomic repulsions between neighboring molecules is avoided. However, the maximum decrease in the intermolecular distance in [Au(tmdt)(2)] was observed along the a direction although there were many intermolecular S...S contacts shorter than the van der Waals distance (3.70 A) along this direction. The shortest intermolecular S...S distance was 2.73 A at 10.7 GPa, which is approximately 1 A shorter than the S...S van der Waals distance (3.70 A). The crystal lattice of [Au(tmdt)(2)] is considered to be stabilized by the enhancement of the intermolecular overlapping of the conduction molecular orbitals having large amplitudes on peripheral S atoms. Although the crystal is composed of 'isolated molecules' like a typical insulating molecular crystal, its compressibility behavior seems to reflect its metallic nature.

Electrical properties of new organic conductor (BEST)(2)InBr(4) [BEST = bis(ethylenediseleno)tetrathiafulvalene] up to 10.8 GPa and antiferromagnetic transition of (BEST)(2)FeBr(4).

A new organic conductor, (BEST)(2)InBr(4), with alternating donor layer arrangement has been synthesized, and the electrical properties have been investigated up to 10.8 GPa. The temperature dependence of the high-pressure resistivity shows a complicated metal-semiconductor transition behavior. The room temperature resistivity decreases with pressure up to 8.6 GPa but increases at higher pressures. The magnetic susceptibility of an isostructural (BEST)(2)FeBr(4) salt shows an antiferromagnetic transition at 4.4 K, which is suppressed with increasing magnetic field.

Structural anomalies associated with antiferromagnetic transition of single-component molecular metal [Au(tmdt)2].

The crystal structure of the single-component molecular metal [Au(tmdt)(2)] was examined by performing powder X-ray diffraction experiments in the temperature range of 9-300 K using a synchrotron radiation source installed at SPring-8. The structural anomalies associated with antiferromagnetic transition were observed around the transition temperature (T(N) = 110 K). The continuous temperature dependence of the unit cell volume and the discontinuous change in the thermal expansion coefficient at T(N) suggested that the antiferromagnetic transition of [Au(tmdt)(2)] is a second-order transition. Au(tmdt)(2) molecules are closely packed in the (021) plane with two-dimensional lattice vectors of a and l (= 2a + b + 2c). The shortest intermolecular S...S distance along the a axis shows a sharp decrease at around T(N), while the temperature dependence of l exhibits a characteristic peak in the same temperature region. A distinct structure anomaly was not observed along the direction perpendicular to the (021) plane. These results suggest that the molecular arrangement in only the (021) plane changes significantly at T(N). Thus, the intermolecular spacing shows anomalous temperature dependence at around T(N) only along that direction where the neighboring tmdt ligands have opposite spins in the antiferromagnetic spin structure model recently derived from ab initio band structure calculations. The results of single-crystal four-probe resistance measurements on extremely small crystals (approximately 25 microm) did not show a distinct resistance anomaly at T(N). The resistance anomaly associated with antiferromagnetic transition, if at all present, is very small. The Au-S bond length decreases sharply at around 110 K; this is consistent with the proposed antiferromagnetic spin distribution model, where the left and right ligands of the same molecule possess opposite spin polarizations. The tendency of the Au-S bond to elongate with decreasing temperature is ascribed to the small energy gap between the pd sigma(-) (or SOMO + 1) and the asym-Lpi(d) (or SOMO) states of the Au(tmdt)(2) molecule.

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). Although single-component molecular metals are composed of molecules, the pressure-induced metallization of a single-component pi molecular crystal while maintaining the initial molecular structure appears to be very difficult.

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.

A unique new multiband molecular conductor: [BDTA][Ni(dmit)2]2.

A new molecular conducting material, [BDTA][Ni(dmit)2]2, with a novel multiband electronic structure has been prepared by simple mixing of precursor salts of the components.

Mn3(HCOO)6: a 3D porous magnet of diamond framework with nodes of Mn-centered MnMn4 tetrahedron and guest-modulated ordering temperature.

Mn3(HCOO)6, a 3D highly stable and flexible porous diamondoid framework based on Mn-centered MnMn4 tetrahedral nodes, exhibits a wide spectrum of guest inclusion behaviour and long-range magnetic ordering with guest-modulated critical temperature.

Freezing of ring-puckering molecular motion and giant dielectric anomalies in metal-organic perovskites.

Pucker up! Metal-organic perovskites containing azetidinium cations, [(CH(2))(3)NH(2)][M(HCOO)(3)] (M = Mn, Cu, Zn), all show a structural phase transition, coupled with the freezing of the ring-puckering molecular motion of azetidinium cations, and an extremely large dielectric anomaly near room temperature. Molecular dynamics simulations showed the freezing of ring-puckering motion of the four-membered-ring azetidinium cation near room temperature.