Hybrid molecular materials based upon organic pi-electron donors and metalcomplexes. Radical salts of bis(ethylenethia)tetrathiafulvalene (BET-TTF) with the octahedral anions hexacyanoferrate(III) and nitroprusside. The first kappa phase in the BET-TTF family

The synthesis, structure, and physical characterization of two new radical salts formed with the organic donor bis(ethylenethia)tetrathiafulvalene (BE T-TTF) and the octahedral anions hexacyanoferrate(III), [Fe(CN)(6)](3-), an d nitroprusside: [Fe(CN)(5)NO](2-), are reported. These salts are (BET-TTF) (4)(NEt4)(2)[Fe(CN)(6)] (1) (monoclinic space group C2/c with a = 38.867(7) Angstrom, b = 8.438(8) Angstrom, 11.239(6) Angstrom, beta = 90.994(9)degre es, V = 3685(4) Angstrom (3), Z = 4) and (BET-TTF)(2)[Fe(CN)(5)NO]. CH2Cl2 (2) (monoclinic space group C2/c with a = 16.237(6) Angstrom, b = 18.097(8) Angstrom, c = 12.663(7) Angstrom, beta = 106.016(9)degrees, V = 3576(3) An gstrom (3). Z = 4). In salt 1 the organic BET-TTF molecules are packed in o rthogonal dimers, forming the first kappa phase observed fur this donor. Th e analysis of the bond distances and the electronic and IR spectra suggests a degree of ionicity of 1/4 per BET-TTF molecule, in agreement with the st oichiometry of the salt. The electrical properties show that 1 is a semicon ductor with a high room-temperature conductivity (11.6 S cm(-1)) and a low activation energy (45 meV), in agreement with the band structure calculatio ns. The magnetic susceptibility of 1 shows, besides the paramagnetic contri bution from the anion, a temperature-independent paramagnetism (TIP) of he Pauli type due to the electronic delocalization observed at high temperatur es in the organic sublattice. This Pauli type paramagnetism is confirmed by the ESR spectra that also show a Dysonian line when the magnetic field is parallel to the conducting plant, typical of metallic and highly conducting systems. Salt 2 presents an unprecedented packing of the organic molecules that form zigzag tunnels where the anions and the solvent molecules are lo cated. The stoichiometry indicates that all the BET-TTF molecules bear a ch arge of +1, and accordingly, 2 behaves as a semiconductor with a very low r oom-temperature conductivity. The magnetic properties of this salt indicate that the unpaired electrons on the organic molecules are strongly antiferr omagnetically coupled, giving rise to a diamagnetic behavior of 2, as the n itroprusside anion is also diamagnetic.