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

✍ Scribed by Franck Thétiot; Florence Bérézovsky; Smaïl Triki; Jean Sala Pala; Carlos J Gómez-García; Amen A Hajem; Sabrina Bouguessa; Jean-Marc Fabre

• Book ID: 104448307
• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 253 KB
• Volume: 6
• Category: Article
• ISSN: 1631-0748
• DOI: 10.1016/s1631-0748(03)00046-8

✦ Synopsis

The electrochemical combination of the paramagnetic anion [Cr(NCS) 6 ] 3-with the organic p-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.