Replacement of 2,2-Bipyridine by 1,4-Diazabutadiene Acceptor Ligands: Why the Bathochromic Shift for [(N(delta)N)IrCl(C5Me5)]^+ Complexes but the Hypsochromic Shift for (N(delta)N)Ir(C5Me5)

Two donor molecules newly synthesized, dimethylthio- and ethylenedithio-tetrathiafulvalenothioquinone-1,3-diselenolemethides (1 and 2), were used to prepare their charge-transfer (CT) salts with a magnetic FeBr4^- counteranion. For 1, a low electrical conducting 1:1 salt (1·FeBr4) was obtained, in which molecules of 1 are tightly dimerized in a one-dimensional (1D) stacking column. On the other hand, 2 gave a 2:1 salt (22·FeBr4) as two different kinds of plate crystals (I and II). Both I and II possess similar stacking structures of molecules of 2 in each 1D column with a half-cut pipelike structure along the c axis. However, for I, the stacking columns are aligned in the same direction along the a and b axes, while for II they are in the same direction along the a axis, but in the reverse direction along the b axis, resulting in the difference in the relative arrangement of molecules of 2 and FeBr4^- ions between the two crystals. The room-temperature electrical conductivities of the single crystals of I and II were 13.6 and 12.7 S cm-1, respectively. The electrical conducting behavior in I was metallic above 170 K but changed to be semiconducting with a very small activation energy of 7.0 meV in the temperature range 4-170 K. In contrast, II showed the semiconducting behavior in the whole temperature range 77-285 K. The corresponding nonmagnetic GaBr4^- salts with almost the same crystal structure as I and II showed definitively different electrical conducting properties in the metal to semiconductor transition temperature in I as well as in the magnitude of activation energy in the semiconducting region of I and II. The interaction between the d spins of FeBr4^- ions was weak and antiferromagnetic in both I and II, but the magnitude of the spin interaction was unexpectedly larger compared with that in the FeBr4^- salt of the corresponding sulfur derivative of 2 with closer contact between the neighboring FeBr4^- ions. These electrical conducting and magnetic results suggest a significant interaction between the conducting electrons and the d spins of FeBr4^- ions located near the columns or layers.