Metallic Conductivity and Ferromagnetic Interaction of Iron(III) d Spins in the Needle Crystals of (Ethylenedithiotetrathiafulvalenoquinone-1,3-dithiolemethide)₂·FeBr₄ Salt

Abstract

The 2:1 charge-transfer (CT) salts (1(2).FeBr(4) and 1(2).GaBr(4)) of ethylenedithiotetrathiafulvalenoquinone-1,3-dithiolemethide (1) with FeBr(4)(-) and GaBr(4)(-) counteranions were obtained as needle crystals, whose structures are almost the same as each other. The 1 molecules form a one dimensionally stacked column with alternation of their molecular axis direction, while the counteranions are aligned in parallel with the 1-stacked columns with the direction of their distorted-tetrahedral geometry maintained. The room-temperature electrical conductivities measured on the single crystals of 1(2).FeBr(4) and 1(2).GaBr(4) were 4.6 and 2.1 S cm(-1), respectively. From the temperature dependences of their electrical conductivities in both cases the electrical conducting properties were metallic between ca. 170 and 300 K, but below ca. 170 K converted to be semiconducting and continued till 5 K, although the activation energies are very small (4-10 meV). For 1(2).FeBr(4) very weak and antiferromagnetic interaction occurred between the d spins of FeBr(4)(-) ions in the temperature range of ca. 1-300 K. However, below ca. 15 K the ferromagnetic interaction was reversely preferential possibly by participation of the pi spin of 1.

Ferromagnetism in a π–d electron system at 1 K

“…For (EDTTFVO) 2 FeBr 4 the exchange interaction between the d spins of FeBr 4 À ions is very weak and antiferromagnetic between 15 and 300 K, but it becomes ferromagnetic at temperatures below 15 K possibly by participation of the p spin of the EDTTFVO donor. The Curie-Weiss fitting to the susceptibility below 15 K presents the ferromagnetic Weiss temperature of +0.87 K, although evidence of the ferromagnetic ordering could not be obtained from the magnetic measurements down to 1.8 K [5].…”

“…Recently, Matsumoto et al [5] succeeded in growing needle crystals of 2:1 salts of new donor molecules, ethyelendithiotetrathiafulvalenoquinone-1,3-dithiolemethide (EDTTFVO) with FeBr 4 À and GaBr 4 À ions. The counteranions are aligned in parallel with the EDTTFVO-stacked columns with maintaining the direction of their distorted-tetrahedral geometry.…”

5-(4,5-Diiodo-1,3-dithiol-2-ylidene)-4′,5′-bis(methylsulfanyl)-2,2′-bi-1,3-dithiol-4(5H)-one

“…New donor molecules featuring a skeleton of tetrathiafulvalenoquinone-1,3-dithiolemethide are used for the preparation of charge transfer (CT) salts with magnetic metal anions (Matsumoto et al, 2002a(Matsumoto et al, ,b, 2003Hiraoka et al, 2007;Sugimoto 2008). In CT salts these molecules can form unique crystal structures with channels in addition to the usual The molecular framework of (I), Fig.…”

(5E)-2-[4,5-Bis(methylsulfanyl)-1,3-dithiol-2-ylidene]-5-(4-iodo-1,3-dithiol-2-ylidene)-1,3-dithiolan-4-one

“…For background to 2,5-di(1,3-dithiole-2-ylidene)-1,3-dithiolan-4-one derivatives, see: Iwamatsu et al (1999); Matsumoto et al (2002Matsumoto et al ( , 2003; Hiraoka et al (2007); Ueda & Yoza (2009). For the synthesis, see: Ueda & Yoza (2009).…”