Anionic Layered Networks Reconstructed from [Cd(SCN)3]∞- Chains in Pseudo One-Dimensional Conducting Salts of Halogenated Tetrathiafulvalenes

The electrocrystallization of diiodo- and dibromo-ethylenedithiotetrathiafuvalene (EDT-TTFI2 and EDT-TTFBr2) in the presence of the polymeric 1D [Et4N][Cd(SCN)(3)] as an electrolyte affords two different salts, formulated as [EDT-TTF-I-2](4)(Cd-3(NCS)(8)]center dot CH3CN center dot H2O (1) and [EDT-TTF-Br-2]10[Cd-5(SCN)(14)]center dot 2TCE (2), characterized by a two-dimensional segregation of the partially oxidized donor molecules and the polymeric anionic network incorporating embedded solvent molecules. Both salts exhibit a partial charge transfer, that is, rho = 0.5 in 1 and an unconventional rho = 0.4 in 2. They behave as semiconductors with sigma(RT) = 0.67 and 33 S cm(-1) and activation energies of 330 and 370 K for 1 and 2, respectively. Compared with a 1:3 Cd/SCN ratio of the starting electrolyte, the reconstructed, thiocyanate (SCN)-deficient motifs [Cd-3(NCS)(8)](2-) and [Cd-5(SCN)(14)](4-) organize into layered hollow structures with cavities filled by solvent molecules, halogen-bonded to the halogenated TTF molecules, through a C-TTF-I center dot center dot center dot N C-CH3 interaction in 1, through a type II C-TTF-Br center dot center dot center dot Cl-C-TCE halogen/halogen interaction in 2. Band structure and Fermi surface calculations for the two salts indicate a two-dimensional character, while the semiconducting properties of the salts are attributed to an efficient nesting of the hidden ID Fermi surfaces.