Magnetic and transport properties of (BEDT-TTF)2X-Sol (X = Br, Cl; Sol = C2H4(OH)2, C3H6(OH)2)

Structure and physical properties of the titled compounds were investigated by means of X-ray diffraction, magnetic susceptibility and electrical resistivity. For (BEDT-TTF)2Br·C2H4(OH)2 the Mott-Hubbard boundary situation is realized, where conduction electrons behave as localized magnetic moments. This salt also shows two-step phase transition, characterized as a structural transition and spin-Peierls transition, respectively. Substitution of the counter anion or solvent molecules also gives two-dimensional Mott-insulators.