Highly Conducting One-Dimensional Systems

The essence of the necessary conditions requires an infinite stack of planar complexes to be aligned with collinear metal atoms that have a short separation (less than the van der Waal radius). This allows strong interactions within a chain, leading to band formation. For the materials discussed the bands are formed through close approach of the collinear metal atoms. For metallic conduction the bands must be partially occupied (filled bands result in semiconducting and insulating properties). Thus, a chain of metal atoms with an extended filled dz2 orbital may form an electron energy band. This band can be metallic only if it is partially occupied this implies that oxidation or partial oxidation depletes electrons from the dzz band and not from the dxy, dxz, dyz, or dxz-yz orbitals. Thus, two important considerations arise the ability to be oxidized and the orbital from which oxidation occurs. 

Prediction of partial oxidation from selected orbitals requires an accurate knowledge of the electronic energy levels. However, the molecular orbital calculations on these transition metal complexes are ambiguous. The ability of the metal to undergo partial oxidation requires two stable oxidation states, e.g., Ir /Ir Pt /Pt. This may not be a rigorous condition as band formation may stabilize a previously uncharacterized oxidation state. The chemical and physical properties of the partially oxidized systems have been the subject of extensive recent work. The results of these studies are described below. 

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