Molecular materials with conducting and magnetic properties based on ET and [ M(tdas)$_{2}]^{x-}$dithiolenes

Two hybrid molecular materials showing a combination of magnetic and conducting properties, the charge-transfer (ET)2[ Fe(tdas)2] (1) and (ET)Ni(tdas)2(2), (ET=bis(ethylenedithio) tetrathiafulvalene; M=Fe, Ni; tdas=1,2,5-thiadiazole-3,4-dithiolate) salts, are characterized by vibrational (IR and Raman) and UV-VIS-NIR spectroscopies. These studies have proved to be effective and diagnostic tools in identifying the oxidation state (partial or integer) and the packing pattern (dimers or segregated stacks) of the ET donor only, since no ν(C=C) group vibration sensitive to the charge of M(tdas)2complexes has been observed. This is ascribed to the extensive electron-delocalization inside the tdas ring in agreement with semiempirical extended Huckel calculations, indicating also that the AO's of the terminal S-atom give a high contribution to the HOMO and favour the occurrence of three-dimensional intermolecular interactions along the molecular longitudinal axis. These findings are consistent with structural results. Key words. Dithiolenes – Molecular Materials – Raman Spectroscopy – Reflectance Spectroscopy.