BDT-TTP-Based π conductors containing divalent magnetic and non-magnetic inorganic anions, [MIICl4]2- (M = Co, Mn, Zn)

Three BDT-TTP [2,5-bis(1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene] salts, (BDT-TTP)(3)[(MCl4)-Cl-II](EtOH)(x) (M = Co, Mn, and Zn; x approximate to 1.0) were prepared. These salts are almost isostructural to one another. The crystals are composed of BDT-TTP columns, BDT-TTP tapes that occupy the interstitial positions between BDT-TTP columns [(MCl4)-Cl-II](2-) anions and the crystal solvents, respectively. These salts showed weakly metallic conducting behavior down to about 150 K. At low temperature, the resistivities increased gradually with decreasing temperature, but the systems retained fairly high conductivities even at around 30 K. The [Z(II)Cl(4)](2-) salt indicated temperature independent paramagnetism down to low temperature. While the susceptibilities of the [(CoCl4)-Cl-II](2-) and [(MnCl4)-Cl-II](2-) salts showed the coexistence of pi conduction electrons and localized high-spins of the magnetic Co-II and Mn-II atoms. no significant pi-d interaction was observed. Band structure calculations were performed with taking account of the possibility of inhomogeneous distribution of pi electrons over the crystallographically independent three BDT-TTP molecules. The system has wide and narrow one-dimensional bands that originate from BDT-TTP columns and tapes, respectively. However, due to the interaction between BDT-TTP columns and tapes, the system gave a unique two-dimensional electronic band. The calculated energy dispersion curves were consistent with the weakly metallic behavior of the systems.