SYNTHESIS, CRYSTAL-CHEMISTRY, ELECTRONIC-STRUCTURE AND MAGNETIC-PROPERTIES OF THE TETRATHIAFULVALENIUM SALT OF TRIS(5,6-DIHYDRO-1,4-DITHIINE-2,3-DITHIOLATO) VANADATE, [TTF][V(DDDT)3] AND THE NEUTRAL PARAMAGNETIC COMPLEX, V(DDDT)CENTER-DOT-3

Oxidation of the monoanionic V(dddt)3- complex (dddt : 5,6-dihydro-1,4 -dithiine-2,3-dithiolato) leads to the formation of either the neutral paramagnetic V(dddt)3. or its solvate, V(dddt)3. DMF. V(dddt)3. cryst allizes in the orthorhombic system, space group Pbcn with a = 15.932 ( 2), b = 10.416 (3), c = 13.292 (5) angstrom, Z = 4; V(dddt)3. DMF crys tallizes in the orthorhombic system, space group Pna2(1) with a = 16.1 93 (4), b = 16.239 (4), c = 10 249 (3) angstrom, Z = 4. In both struct ures, the neutral paramagnetic molecule exhibits a distorted trigonal prismatic coordination around the vanadium atom, which differs from th e perfect trigonal prismatic geometry of V(dddt)3-. The folding of the ligand plane with respect to the VS2 plane observed for V(dddt)3- and not present in V(dddt)3. is shown to be consistent with extended Huck el calculations (total energy as a function of the folding angel and n ature of the complex HOMO). Corrugated layers are identified in the so lid state. These stack on top of each other in V(dddt); and are shifte d in V(dddt)3. DMF. In the latter, the shift of these robust corrugate d sheets creates channels which are filled by disordered solvent molec ules. Oxidation of V(dddt)3- in the presence of tetrathiafulvalene (TT F) affords the 1:1 [TTF][V(dddt)3] salt whose structure was determined at 297 and 140 K. No phase transition is observed between these tempe ratures. At 297 K, the salt crystallizes in the monoclinic system, spa ce group P2(1)/c with a = 15.373 (3), b = 10.061 (3), c = 19.142 (3) a ngstrom, beta = 95.15 (1)degrees, Z = 4. The perfect trigonal prismati c V(dddt)3- anions form hexagonal close-packed layers. The layers are separated by dicationic TTF dimers, (TTF+.)2, located in the octahedra l sites of the pseudo-cubic face-centered array of the anions in a way reminiscent of the prototypical CdCl2 structure. This material is ins ulating and exhibits a chi = A . T(-alpha) law characteristic of the p resence of a small amount of slightly interacting paramagnetic species mainly located on the TTF dimers, as demonstrated by the determinatio n of the fine structure tensor principal axis system.