Nuclear Relaxation in Two Conductive TCNQ Salts

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Abstract
As shown by recent studies1 the frequency dependence of the nuclear relaxation rate is a sensitive probe of spin dynamics in 1D system. We have investigated by this method the properties of two conductive TCNQ salts: N-Methyl-Phenazinium (NMP) TCNQ and Quinolinium (Qn) TCNQ2, We have measured the proton relaxation time T1 as a function of the nuclear Larmor frequency vN between 7 and 100 MHz. The measurements have been performed at room temperature on polycristalline samples. The nuclear relaxation rates are plotted in Figures 1 and 2 versus vN −1/2. We obtain straight lines on the entire frequency range from 7 to 100 MHz for Qn TCNQ, and only from 40 to 100 MHz for NMP TCNQ. This is the experimental evidence of a 1D diffusive motion for the electronic spins in these compounds. The aim of this paper is to attempt a qualitative explanation of such a behaviour, which was not reported so far in conductive TCNQ salts.