SYNCHROTRON-RADIATION PHOTOEMISSION-STUDY OF IN-SITU SYNTHESIZED DCNQI(N,N'-DICYANOQUINONEDIIMINE)-CU SALTS

A photoemission study using synchrotron radiation of in-situ synthesiz ed organic conductors (DMe-DCNQI)2Cu and (MeBr-DCNQI)2Cu is reported, where DMe-DCNQI and MeBr-DCNQI are dimethyl-N,N'-dicyanoquinonediimine and methyl, bromine-N,N'-dicyanoquinonediimine, respectively. The pho ton energy dependence of the valence band spectra is used to character ize the origin of the observed features. In both salts, the Cu 3d deri ved states are situated at 3.5-4 eV binding energy, while the C and N 2psigma states appear around 7.5 eV. The Br 4p states are found around 5 eV in (MeBr-DCNQI)2Cu. The states near the Fermi level have substan tial C and N 2ppi character consistent with extended Huckel molecular orbital calculations. The absence of a resonance at the Cu 3p threshol d suggests a small contribution of Cu2+ configuration in DCNQI-Cu salt s.