Extended-Hückel Energy Band Structures of Organometallic Compounds with One-Dimensional Crystal Geometries

In order to rationalize the high electrical conductivity of 2,5-dimethyl-N,N'-dicyanoquinonediimine radical anion salts (2,5-DM-DCNQI) of copper, silver, and lithium, we performed onedimensional energy band structure calculations of extended-Hückel type (namely Self-Consistence of Charge, SCC) for one-dimensional models of these "organic conductors". In each case, SCC yields two overlapping incompletely occupied valence bands, which give rise to some evidence for the observed high electrical conductivity, in spite of the one-electron nature of the method. Furthermore, these two frontier energy bands do not contain any metallic orbital contribution, which suggests that the electron transport takes place in the organic stack of the 2,5-DM-DCNQI ligands only.