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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]

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]

Abstract: The electronic structures of infinite linear metallic chains have been examined by tight-binding band calculations. We have analyzed the band structures of these linear metallic chains, density of states, and Mulliken overlap populations. The band structure of the linear Rh and Ru chain possesses diffuse d bands that traverse the Fermi level, similar to that of the linear Cr and Co chain. On the other hand, the linear Cu chain possesses some narrow 4s bands in energy levels near the Fermi level. Changing the metal atoms of the central metallic chain can provide various electronic states. [Copyright &y& Elsevier]

The electronic structure of linear homocatenated indium (In) polymer has been studied by tight-binding band calculations with the extended Huckel approximation. The polymer was found to have semiconducting behavior with a direct gap. The highest occupied crystal orbital (HOCO) of the polymer are formed by σ-bonding between neighboring p orbitals of In atoms, whose σ-electrons were well delocalized along the main chain. The possible presence of σ-conjugation in the chains can result in σ - σ* interband transitions, as in the case of polysilane, which is formed by group 14 elements. [ABSTRACT FROM AUTHOR]

The band structures of metallocene-based polymers in which the nearest metalloecenes were directly linked by a C-C bond have been determined by employing the tight-binding crystal orbital (CO) method. In particular, we determined the band structures of metallocene-based alternate copolymers whose metal sequences in a unit cell were Fe-Co, Fe-Fe-Co-Co, Fe-Ni, Ru-Co and Os-Co. The band structures of alternate copolymers of Fe-Co and Fe-Ni possessed a partially occupied (PO) band whose crystal orbitals were extremely localized at the 3d orbitals of cobalt or nickel atom. Alternate copolymers of Ru-Co and Os-Co had the same tendency as that of band structure of Fe-Co. Therefore, it was clear that the band structures of the metallocene-based alternate copolymers were considered to be a superposition of the polymetallocenylenes. Furthermore, we examined the effect of inserting the bridging part of boron-, phosphorus-, and sulfur bridges between the nearest ferrocenes upon the band structures of ferrocene-based polymers. The electronic structure of the boron-bridged polymer was similar to that of the silicon-bridged polymer whose band structure was determined in our previous study. On the other hand, the phosphorus- and sulfur-bridged polymers yielded two degenerated HO bands whose COs were localized at P or S 2p orbitals. [ABSTRACT FROM AUTHOR]

Abstract: The band structures of polymers containing first row transition metal metallocenes were calculated using the one-dimensional tight-binding crystal orbital method along with the extended Hückel approximation. The metallocene polymers, except for ferrocene and chromocene polymers, possessed a partially occupied band. The ferrocene and chromocene polymers exhibit semiconductor character. Cobaltocene, nickelocene, and vanadocene polymers have a metallic character. The manganocene polymer has a partially occupied band that is localised. A change in the band structures of the metallocene polymers was compatible with an alternation of the energy levels of the band of the transition metals. [Copyright &y& Elsevier]

Abstract: The electronic structures of ferrocene-containing polymers with heteroatom-bridges have been examined using the tight-binding crystal orbital method. The relationship between the band structures of the polymers and their bridging moieties was examined. The highest occupied (HO) band of the polymers with saturated carbon-bridges consisted of π-type p orbitals of cyclopentadienyl ring. On the other hand, the polymers with silicon-bridges possessed a localised HO band, which was formed by orbitals of iron atom. [Copyright &y& Elsevier]

Abstract: Electronic structures of polymers, ferrocene (Cp2Fe, Cp=η5-C5H5) in the main chain, were examined using the tight-binding crystal orbital method. Attention was focused on the manner in which the band structures of the polymers were influenced by the bridging moieties between the ferrocenes. Ferrocene-containing polymers with unsaturated carbon bridges possessed relatively wide bandwidths of both the highest occupied band and the lowest unoccupied band. Although the π conjugation was broken at the iron atoms, the unsaturated carbon bridges could form limited delocalization of the π electrons between the neighbouring Cp rings via the bridging moieties. [Copyright &y& Elsevier]

I present a theoretical study of the electronic transport properties of nickelocenylferrocene sandwiched between gold electrodes. Compared with the biferrocene system, the nickelocenylferrocene system had high electrical conduction and rectification in the bias range -1 to 1 V. Furthermore, the spin-down states of the nickelocenylferrocene system exhibited perfect spin-filtering properties. From the electronic states of the nickelocenylferrocene, it was found that the rectification was caused by a difference in the bias-dependent behaviors between the Fe 3d and Ni 3d orbitals. [ABSTRACT FROM AUTHOR]