Dual-Layered Quasi-Two-Dimensional Organic Conductors with Presumable Incoherent Electron Transport



We have prepared a series of BEDT-TTF or BETS-based radical-cation salts (D)4MBr4(C6H6–nXn) with tetrahedral anions [MIIBr4]2– (D = BETS, BEDT-TTF; X = F, Cl, Br; n = 1, 2). The salts (D)4MBr4(C6H6–nXn) are characterized by the different structures of neighboring conducting layers, structural phase transitions, and different types of conductivity, namely, metallic and semiconducting, along and across the conducting layers, respectively. The Fermi surface of the metallic layer of (D)4MBr4(C6H6–nXn) with alternating crystallographically different conducting layers (dual-layered salts) provides a roadmap for interpreting the transport properties of quasi-two-dimensional organic conductors. This review reports on the structures of these compounds, the effect of MBr4 anions and solvent on the occurrence of phase transitions, different Fermi surface topologies in connection with the different structures of neighboring conducting layers, and the possibility of the incoherent transport of charge carriers in such systems.