Electro-Conductive Single-Molecule Magnet Composed of a Dysprosium(III)-Phthalocyaninato Double-Decker Complex with Magnetoresistance.

A one-dimensional (1D) arrangement of an unsubstituted partially oxidized Dy3+ double-decker complex, [DyPc2 ]Ix (Pc=phthalocyaninato, I=iodide; 1.93

Atomic-Scale Origin of the Quasi-One-Dimensional Metallic Conductivity in Strontium Niobates with Perovskite-Related Layered Structures.

The quasi-one-dimensional (1D) metallic conductivity of the perovskite-related SrnNbnO3n+2 compounds is of continuing fundamental physical interest as well as being important for developing advanced electronic devices. The SrnNbnO3n+2 compounds can be derived by introducing additional oxygen into the SrNbO3 perovskite. However, the physical origin for the transition of electrical properties from the three-dimensional (3D) isotropic conductivity in SrNbO3 to the quasi-1D metallic conductivity in SrnNbnO3n+2 requires more in-depth clarification. Here we combine advanced transmission electron microscopy with atomistic first-principles calculations to unambiguously determine the atomic and electronic structures of the SrnNbnO3n+2 compounds and reveal the underlying mechanism for their quasi-1D metallic conductivity. We demonstrate that the local electrical conductivity in the SrnNbnO3n+2 compounds directly depends on the configuration of the NbO6 octahedra in local regions. These findings will shed light on the realization of two-dimensional (2D) electrical conductivity from a bulk material, namely by segmenting a 3D conductor into a stack of 2D conducting thin layers.

New aspects of π-d interactions in magnetic molecular conductors.

The 2 : 1 cation radical salts of bent donor molecules of ethylenedithio-tetrathiafulvalenoquinone-1,3-dithiolemethide (EDT-TTFVO), ethylenedithio-diselenadithiafulvalenoquinone-1,3-dithiolemethide (EDT-DSDTFVO), ethylenedithio-diselenadithiafulvalenothioquinone-1,3-diselenolemethide (EDT-DSDTFVSDS), ethylenedioxy-tetrathiafulvalenoquinone-1,3-dithiolemethide (EDO-TTFVO) and ethylenedioxy-tetrathiafulvalenoquinone-1,3-diselenolemethide (EDO-TTFVODS) with FeX4- (X = Cl, Br) ions are prepared by electrocrystallization. The crystal structures of these salts are composed of alternately stacked donor molecule and magnetic anion layers. The band structures of the donor molecule layers are calculated using the overlap integrals between neighboring donor molecules and are compared with the observed electronic transport properties. The magnetic ordering of the Fe(III) d spins of FeX4- ions is determined from magnetization and heat capacity measurements. The magnetic ordering temperatures are estimated by considering a combination of a direct d-d interaction between the d spins and an indirect π-d interaction between the conduction π electron and the d spins, whose magnitudes are separately calculated from the crystal structures with an extended Hückel molecular orbital method. The occurrence of a π-d interaction is proved by the negative magnetoresistance, and the magnitude of magnetoresistance reflects the strength of the π-d interaction. The effect of pressure on the magnetoresistance is studied, and the result indicates that the magnitude of magnetoresistance increases, namely, the π-d interaction is enhanced with increasing pressure. From these experimental results it is shown that (EDT-TTFVO)2•FeBr4 is a ferromagnetic semiconductor, (EDT-DSDTFVO)2•FeX4 (X = Cl, Br) and (EDT-DSDTFVSDS)2•FeBr4 are metals exhibiting antiferromagnetic ordering of the d spins, and (EDO-TTFVO)2•FeCl4 and (EDO-TTFVODS)2•FeBr4•(DCE)0.5 (DCE =-dichloroethane) are genuine antiferromagnetic metals. Among them, the (EDT-TTFVO)2•FeBr4 salt is the first π-d molecular system where the d spins of FeBr4- ions are ferromagnetically ordered through antiferromagnetic interaction with the conduction π electrons. Corresponding to this ferromagnetic ordering, an anomalous dielectric slow-down phenomenon toward the ordering temperature is observed. The π-d interaction in (EDT-DSDTFVSDS)2•FeBr4 is very large and comparable to that in λ-(BETS)2•FeCl4, which has the highest reported value so far, while the d-d interaction is fairly small. Concerning the ratio between the magnitudes of π-d and d-d interactions (Jπd/Jdd), this salt is currently the best π-d molecular system.