A new donor (ST-STP), in which tetrathiafulvalene and tetraselenafulvalene are fused, has been synthesized. This donor shows unexpectedly large on-site Coulomb repulsion compared with other bis-fused TTF systems. In (ST-STP)ReO4, intramolecular charge disproportionation is suggested by the crystal structure and transport properties.

Bis-fused donors composed of (thio)pyran-4-ylidene-1,3-dithiole and tetraselenafulvalene (1a, 2a) and their bis(methylthio) derivatives (1b, 2b) were synthesized. Cyclic voltamograms of all the donors consisted of four pairs of one-electron redox waves, and it was suggested that a positive charge of 1 +• and 2 +• distributed mainly on the (thio)pyran-4-ylidene-1,3-dithiole moiety. X-ray structure analysis revealed that (1b)PF 6 (C 6 H 5 Cl) 0.5 and (2b)PF 6 (C 6 H 5 Cl) formed one-dimensional conducting stacks in which the donors were dimerized or tetramerized. In those salts, intramolecular charge disproportionation of the donors was suggested by X-ray structure analysis and density functional theory (DFT) calculation with UB3LYP/6-31G(d) basis function. A tightbinding band calculation suggested that these materials were band insulators. All the donors gave highly conducting TCNQ (7,7,8,8-tetracyanoquinodimethane) complexes and I 3 − salts (σ rt = 0.3-19 S cm −1 on a compressed pellet) with very low activation energies of 0.017-0.040 eV, while single crystals of (1b)PF 6 (C 6 H 5 Cl) 0.5 and (2b)PF 6 (C 6 H 5 Cl) exhibited semiconductive behavior with large activation energies (E a = 0.16-0.22 eV).

Novel Bis-Fused π-Electron Donor Composed of Tetrathiafulvalene and Tetraselenafulvalene. -Title compound (VI)(space group P21a; Z=4) shows unexpectedly large on-site Coloumb repulsion compared to other bis-fused tetrathiafulvalene systems. -(ASHIZAWA, M.; ISHIDZU, K.-I.; WATANABE, M.; TANAHASHI, T.; SHIRAHATA, T.; KAWAMOTO, T.; MORI, T.; MISAKI*, Y.; Chem. Lett. 39 (2010) 10, 1093-1095, http://dx.