PHOTOEMISSION-STUDY ON THE VALENCE BANDS OF DME-DCNQI DERIVED CHARGE-TRANSFER SALTS

The electronic structure of crystalline needles of the 2,5-Dimethyl substituted (DCNQI)2M (M = Cu, Rb, Cs) radical-anion salts, prepared in situ, is determined by photoelectron spectroscopy using synchrotron radiation. The electronic structure at the top of the valence bands is determined to arise mainly from contributions of C2p and N2p states. In particular, the Cu3d atomic levels do not contribute significantly to the density of states next to the Fermi energy. This comparison of salts with different central atoms gives the first experimental evidence of a truely organic metal with the uppermost (conducting) band originating from C2p and N2p derived states.