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

The electronic state of a new group of DCNQI-Metal complexes, (DI-DCNQI)2M (M=Li, Cu, Ag), has been studied by the electric resistance, R, magnetic susceptibility, χ, 1H- and 13C-NMR measurements. The newly synthesized complexes, (DI-DCNQI)2Ag and (DI-DCNQI)2Li, 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 4kF charge density wave. The Cu salt of the DI-system is known to be metallic down to low temperatures. The hybridization of the 3d orbitals of Cu ions with the LUMO of DI-DCNQI is demonstrated by the measurements of temperature dependence of χ and Kight shift of 1H- and 13C-NMR on the cyano site.