Abstract
Pressure coefficients of the spin susceptibility, nuclear relaxation rates and resistivity have been measured in TTF-TCNQ, TMTTF-TCNQ and HMTSF-TCNQ. We point out that the very large pressure coefficients are not in agreement with the significantly smaller coefficients measured in optical absorption experiments under pressure. We propose an explanation of the magnetic properties of TTF-TCNQ and related compounds in terms of itinerant one dimensional antiferromagnetism. Using the Shiba-Pincus Hubbard model calculation we derive a value U/4t 1 close to unity which points towards the importance of correlations in the TTF-TCNQ family.