Electron Spin Resonance of Highly Anisotroic Organic Systems

After a brief discussion concerning the chemical nature and structural organization, ESR results obtained on low and highly conducting quasi one-dimensional organic systems, are presented. Related to the knowledge of the molecular properties, invaluable informations about the properties of the linear chains may be obtained on single crystals from the susceptibility, the g tensor and the line shape: existence of magnetically inequivalent sites, respective contributions of the different magnetic species (for low conducting systems) or of the different chains (for highly conducting systems). In particular cases, the existence of weak intrachain coupling has been pointed out and even some order of magnitude for the ratio of intra- to interchain exchange have been reached.