Comparative study on the magnetism and conductivity of (DI-DCNQI) 2 M, (M=Li, Cu, Ag)

The electronic state of a new group of DCNQI-Metal complexes, (DI-DCNQI) 2 M (M=Li, Cu, Ag), has been studied by the electric resistance, R, magnetic susceptibility, χ, 1 H- and 13 C-NMR measurements. The newly synthesized complexes, (DI-DCNQI) 2 Ag and (DI-DCNQI) 2 Li, are paramagnetic insulators below room temperature. An antiferromagnetic ordering was found at least in the Ag salt. This is the first case, in the DCNQI-Metal complexes, that the π electrons on the DCNQI molecules exhibit an antiferromagnetic state. The insulating state of the Ag salt is considered as a Mott insulator associated with freezing of 4 k F charge density wave. The Cu salt of the DI-system is known to be metallic down to low temperatures. The hybridization of the 3 d orbitals of Cu ions with the LUMO of DI-DCNQI is demonstrated by the measurements of temperature dependence of χ and Kight shift of 1 H- and 13 C-NMR on the cyano site.