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-I2]4[Cd3(NCS)8]·CH3CN·H2O (1) and [EDT-TTF-Br2]10[Cd5(SCN)14]·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, ρ = 0.5 in 1 and an unconventional ρ = 0.4 in 2. They behave as semiconductors with σRT = 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 [Cd3(NCS)8]2− and [Cd5(SCN)14]4− organize into layered hollow structures with cavities filled by solvent molecules, halogen-bonded to the halogenated TTF molecules, through a CTTF−I···NC−CH3 interaction in 1, through a type II CTTF−Br···Cl−CTCE 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 1D Fermi surfaces.