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Single-molecule electric current of pyrrole oligomers, as a model of p-type doped polypyrrole, was studied theoretically using the first-principles calculation method. Elementary excitations in doped polypyrrole, such as polaron and bipolaron, were modeled in this study as cation and singlet-dication, respectively. The oligomer was sandwiched between the ferromagnetic nickel electrodes, of which magnetic alignment was varied from parallel to antiparallel to confirm tunnel magnetoresistance (TMR) by a difference of electric currents under each magnetic configuration. Although the values of the electric current of the doping state increased compared to that of the neutral state, the TMR performance of the polaron state deteriorated compared to that of the neutral state, and the TMR performance of the bipolaron exceeded that of the neutral state. Therefore, it was found that the completed p-type doping state of the bipolaron improved the TMR effect performance. Image 1 • Single-molecule electric current of pyrrole oligomers. • Elementary excitations in doped polypyrrole. • Tunnel magnetoresistance. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Polysilane was modified with methacrylate having a protected isocyanate. • Polysilane was used as a photoinitiator for radical polymerization reactions. • A hybrid nanoscale material was prepared from a mixture of the modified polysilane and polyol. Abstract Polysilane was modified with methacrylate having a protected isocyanate using the polysilane itself as a photoinitiator for radical polymerization reactions. Although the photoreaction decreased the length of σ-conjugation in the polysilane block, the ultraviolet absorption properties derived from σ-conjugation were retained for the polysilane block. The polysilane modified with protected isocyanate exhibited the functionality and reactivity of isocyanate, and thus could react with the alcohol group in a polyol by deprotection of the protected isocyanate to form a hybrid material in which polysilane was combined with polyol on the nanoscale. [ABSTRACT FROM AUTHOR]

Spin current in π-cyclopentadienyl (Cp) complexes of the main group elements have been studied by the first-principles method of density functional theory. The characteristics of spin current were examined by using a model of Cp-metal complex, sandwiched between ferromagnetic electrodes. Spin currents were varied by changing the main group element. The Cp complex of the p-block main group elements showed a tunnel magnetoresistance (TMR) effect at a low bias voltage, while that of the s-block main group elements did not show this effect. This is because the spin-filtering effect under a parallel alignment of ferromagnetic electrodes is deeply linked to the TMR effect. The bonding state between the Cp ring and the metal atom, whether covalent or ionic bond, was the important factor responsible for the TMR effect. [ABSTRACT FROM AUTHOR]

Tunnel magnetoresistance (TMR) of diamondoids has been predicted by first principles density functional theory. Diamantane was used as a basic molecular proxy for diamondoids because hydrogen atoms in the apical position are easily substituted for a thiol group. The pristine diamantane exhibited a low TMR ratio of 7%, and boron-substitution considerably decreased the TMR ratio. Conversely, nitrogen-substitution enhanced the TMR ratio by up to 20%. Heteroatom-substitution changes the tunneling probabilities by varying the molecular bond lengths. Furthermore, when the spins of the electrodes are parallel, the heteroatoms resulted in transmittance probabilities at an energy range near the Fermi level. Consequently, heteroatom-substitution can control the TMR ratios of diamondoids very well. [ABSTRACT FROM AUTHOR]

The electronic transport properties of diamantanes as a model of diamondoids (nanodiamonds) were studied by first-principles calculations. For this purpose, diamantane with thiol group was sandwiched between gold electrodes. Additionally, the effect of substitution of equatorial tertiary carbons on conductance was examined in detail. The conductance of boron- and phosphorus-substituted diamantanes was nearly the same as that of non-substituted diamantane, whereas the conductance of nitrogen-doped diamantane was higher. This is due to the fact that the nitrogen-substitution increases the transmittance at the Fermi level by the overlap of nitrogen 2p and sulfur 3s orbitals. Furthermore, the heteroatom-substituted diamantanes exhibited current rectification to a certain degree. [ABSTRACT FROM AUTHOR]

Spin conduction by a molecule-containing nitroxide radicals linked via a phenylene coupling unit was estimated by calculating the transmission of electrons in the molecule when sandwiched between two semi-infinite periodic gold crystals. Nitroxides linked via a m -phenylene coupling unit showed a large splitting in the energy of the transmission peaks of α- and β-spins, whereas this energy splitting was smaller for molecules with extended π-conjugation, such as nitroxides linked via a p -phenylene coupling unit. The energy splitting of transmission is influenced by spin polarization and constructive/destructive interference of radicals through the phenylene coupling unit. [ABSTRACT FROM AUTHOR]

Abstract: Spin transport in bimetallic pentalene complexes (CpM(pentalene)M′Cp;M,M′=Fe,Co,Ni) between two gold electrodes was investigated, using a Green’s function formalism under density functional theory. Variation of the metal atom species in the complexes gives a considerable change in their spin properties, with hetero-bimetallic complexes containing an odd number of electrons exhibiting spin filter behaviour. In contrast, alternation in the contact condition, whether Cp-anchoring or adducting by sulphur–gold bonds, had almost no effect on spin filter behaviour, but did lead to variation in electrical conduction. We examined suitable bimetallic pentalene complexes in order to enhance their spin filter efficiency. [Copyright &y& Elsevier]

Abstract: The electronic structures of oligomeric and polymeric -cyclopentadienyl (Cp)–indium complexes were examined by tight-binding band calculations. On the basis of the band structures, we discuss the delocalization of electrons along the axis of the polymer chain. In order to discuss the application of this polymeric complex to nano/molecular electronic devices, it is important to consider its interaction with a metal electrode. Therefore, we also examined the electronic structures of an oligomeric Cp–In complex adsorbed on a metal slab (Pt or Au). [Copyright &y& Elsevier]

The electronic transport properties of silicon clusters were examined via theoretical calculations using the first-principles method. Additionally, p-type doping and n-type doping were analyzed by calculating conductance and current of boron- and phosphorus-doped silicon clusters. The p-type doping and n-type doping provided a new transmission peak at an energy level around the Fermi level to increase conductance. Furthermore, simultaneous boron and phosphorus doping resulted in noticeable rectifying characteristics, with the current drive in forward bias being three times higher than that in the reverse bias. A p–n junction was achieved even on a molecular scale. [ABSTRACT FROM AUTHOR]

Abstract: Band structures of organometallic polymers containing μ2-bridging pentalene or indacene as ligands for transition metals (Fe, Co, Ni) have been calculated by using the tight-binding crystal orbital method. These organometallic polymers are an infinite model of bimetallic complexes of pentalene or s-indacene with pentamethylcyclopentadiene. Polymers containing pentalene and s-indacene with iron atoms possess small band gaps with broad bands near the Fermi level. On the other hand, polymers containing cobalt or nickel atoms exhibit a metallic or semi-metallic character, which suggests the possibility of changes in their structures. We have analysed the crystal orbital phases to examine the electronic structures. [Copyright &y& Elsevier]

Abstract: A band structure of the infinite linear organometallic chain, which is considered to be the limiting case of linear metal (Cr, Co and Ni) complexes with ligands, has been investigated using the tight-binding calculation including both and electrons. From the band structures, we predict the electronic properties of the organometallic chain. A linear Ni chain has a direct semiconductor gap with a narrow bandwidth for the highest occupied band, whose molecular orbital is localised on the ligand strands. On the other hand, a linear Cr or Co chain exhibits a metallic character that is dependent on the delocalised 3d orbitals. [Copyright &y& Elsevier]

Poly(methylphenylsilane) (PMPS)/3-methacryloxypropyltriethoxysilane (MPTES) block copolymer (P(MPS-co-MPTES)) has been applied to formation of polysilane–titania hybrid thin film via sol–gel reaction. We have successfully prepared a homogeneous and transparent polysilane–titania hybrid thin film with higher photo-durability than polysilane or polysilane–silica hybrid thin film. The surface of the polysilane–titania hybrid thin film had numerous unevenness approximately 10–20 nm a few hundred nm intervals after UV irradiation. [Copyright &y& Elsevier]

Various polysilane–acrylamide block copolymers have been prepared from photopolymerization of acrylamide-type monomers using poly(methylphenylsilane) (PMPS) as a macro-photo-radical initiator. The acrylamide block in the copolymers improved the hydrophilic property of PMPS. These PMPS–acrylamide block copolymers have been applied to formation of PMPS–silica hybrid thin films via sol–gel reaction. Homogeneous and transparent PMPS–silica hybrid thin films were obtained from a few PMPS–acrylamide block copolymers. It was found for these hybrid thin films based on hydrogen bonding formation between amide group and silanol group. The surface properties of hybrid thin films were evaluated by water contact angle measurement, scanning electron microscope (SEM), and atomic force microscope (AFM) images. [ABSTRACT FROM AUTHOR]

• Coherent electron transport in a DNA molecule. • DNA conformational transition. • A change in the magnetoresistance ratio. A DNA molecule formed by a cytosine-guanine sequence ((CG) n) exhibits a conformational transition from the B-form to the Z-form by varying the ionic environment. This study reports coherent spin transport in a molecule of double strand 5′-(CG) n -3′ (n = 2, 3, 4) under a magnetic proximity effect from ferromagnetic nickel electrodes. The calculation was performed by using a Landauer-Büttiker formula based on a non-equilibrium Green's function with density functional theory. The conformational transition led to about a 10 times change in conductance, which is similar to the experimental results. In addition, the absolute value of the tunnel magnetoresistance ratio had a tendency to decrease with the conformational transition. The calculation result suggests that not only a change in conductance but also a change in the magnetoresistance ratio can be used to monitor the conformation of a DNA molecule sensitively. [ABSTRACT FROM AUTHOR]