Magnetic Susceptibility and ESR Studies of Highly Conductive CuL(TCNQ)2Incorporating 2,2′-Bipyridine or Ethylenediamine as Ligand

Electron spin resonance spectra were recorded on highly conducting CuL(TCNQ)2 (L: 2,2′-bipyridine or ethylenediamine) at different temperatures. The observed g values increased with decreasing temperature. On the basis of the g shift and the static susceptibility observed, a local magnetic susceptibility contributed from Cu and that from TCNQ, were evaluated individually. The local Cu susceptibility is of the Curie type. The Curie constant indicates that each Cu atom carries 0.05 umpaired electron on the average in Cu(bpy)(TCNQ)2 and 0.07 in Cu(en)(TCNQ)2: the average oxidation number of copper is equal to 1.05 in the former and 1.07 in the latter. The local susceptibility of TCNQ can be interpreted by a narrow band model in which the susceptibility is given by the sum of the Curie term and a temperature-independent paramagnetic term.This suggests that the TCNQ arrays have inherently metallic nature.