Radical anion salts of N,N′-dicyanoquinonediimine (DCNQI): Conductivity and magnetic properties

Abstract

DC-conductivity (σ), static susceptibility (χ), ESR-intensity, resonance position and linewidth of (R 1,R 2-N,N′ -DCNQI) 2Me ( R 1 = CH 3; R 2 = CH 3, Cl, Br; Me = Ag, Cu) between 300 K and 1.2 K are reported. All copper salts have a high χ of about 5 – 6.10 −4 emu/mole in the conducting temperature range. This can be explained by strong electron-electron repulsion. In two salts, a CDW driven phase transition is seen and antiferromagnetic resonance (AFMR) is found below 10 K. The lack of any ESR signal in the conducting state is due to strong spin-orbit coupling (SOC) given by the nitrogen(p)-Cu(d) admixture which implies some electronic transport across the stacks. The silver salts do not exhibit these features. They behave as quasi-one dimensional conductors with reduced SOC effects. The conductivity is limited solely to the anion stack. Consequently, 1D-localization effects dominate the temperature dependence of the conductivity.