New charge transfer salts of two organic π-donors of the tetrathiafulvalene type with the paramagnetic [Cr(NCS)6]3– anion

The electrochemical combination of the paramagnetic anion [Cr(NCS) 6 ] 3– with the organic π-donors bis(ethylenedithio)tetrathiafulvalene (ET) and 4,5-bis(2-hydroxyethylthio)-4′,5′-ethylenedithiotetrathiafulvalene (DHET–EDTTTF) leads to two new radical cation salts, namely (ET) 4 [Cr(NCS) 6 ]·PhCN ( 1 ) and (DHET– EDTTTF) 2 (NEt 4 )[Cr(NCS) 6 ] ( 2 ). Both have been characterized by X-ray crystallography, magnetic and resistivity measurements. The structure of 1 consists of alternating inorganic layers generated by the anions and organic layers in which the PhCN molecules are inserted; the organic sub-lattice is built up from four different ET units, three of them with a charge distribution of +1, the fourth being neutral. The organic sub-lattice of 2 contains a centrosymmetric [(DHET–EDTTTF • ) 2 ] 2+ dimer, in which the overlap mode is of the eclipsed type. Conductivity measurements indicate that compounds 1 and 2 are semiconductors with room temperature conductivities of 1.4 × 10 –2 and 6.1 × 10 –5 S cm –1 and activation energies of 0.24 and 0.23 eV, in 1 and 2 , respectively. For both salts, magnetic measurements indicate ( i ) that the organic and inorganic parts are magnetically independent, and ( ii ) that the organic units are antiferromagnetically coupled.