PREPARATIONS, X-RAY CRYSTAL-STRUCTURES, EH BAND CALCULATIONS, AND PHYSICAL-PROPERTIES OF [(TTF)6(H)(XM12O40)(ET4N)] (M = W, MO X = P, SI) - EVIDENCE OF ELECTRON-TRANSFER BETWEEN ORGANIC DONORS AND POLYOXOMETALATES

The preparation, X-ray crystal structures, and conducting, optical, ESR, and magnetic properties of the (TTF)6(H)(XM12O40)(Et4N) salts are reported [1, X = P, M = W; 2, X = Si, M = W; 3, X = P, M = Mo; 4, X = Si, M = Mo]. The four compounds are isostructural and crystallize in the orthorhombic space group Cmmm. 1: M(r) = 4234.54; a = 15.563 (8), b = 19.497 (8), c = 14.178 (7) angstrom, V = 4302 angstrom3, Z = 2, d(calc) = 3.269 g CM-3, R = 0.040. 2: M(r) = 4231.65; a = 15.460 (8), b = 19.357 (5), c = 14.154 (3), V = 4235.7 angstrom3 Z = 2, d(calc) = 3.318 g cm-3; R = 0.069. 3: Mr = 3179.6; a = 15.383 (2), b = 19.284 (5), c = 14.088 (9) angstrom, V = 4179.3 angstrom3, Z = 2, d(calc) = 2.527 g CM-3, R = 0.039. 4: M(r) = 3176.7; a = 15.455 (7) angstrom, b = 19.262 (8) angstrom, c = 14.089 (3) angstrom, V = 41'94.3 angstrom3, z = 2, d(calc), = 2.515 g CM-3 , R = 0.050. Four out of the six TTF molecules form regular stacks with eclipsed overlaps, running along the [001] direction in channels formed by the inorganiC [XM12O40] blocks and the two remaining isolated TTF. Magnetic susceptibility measurements indicate the presence of one unpaired electron per formula unit in the phosphometalate compounds (1 and 3), while the silicometalate compounds (2 and 4) exhibit a diamagnetic behavior. Accordingly, we observe ESR signal corresponding to W5+ and Mo5+ in the phosphometalate salts. The results obtained from physical measurements and band structure calculations suggest (TTF2)0(TTF4)2+(H)+(Et4N)+-(XM12O40)4- as being the appropriate formula for all of the four salts.