Electron-proton couplings and local susceptibilities in TTF and TCNQ salts

Proton NMR lines have been recorded at 250 MHz in different selectively deuterated TTF and TCNQ compounds. An evaluation of the isotropic hyperfine coupling (a) is obtained from the paramagnetic shift of the line, while the second moment leads to an experimental determination of the dipolar coupling (d). It is established that the dipolar coupling for TTF and TCNQ protons is not at all negligible. For both molecules one has d ≃ 1/2 a = 0.6 gauss. Further, estimates of the local susceptibilities in TTF TCNQ and NMP TCNQ are given.