A new Ni(dmit)2-based organic magnetic charge-transfer salt, (m-PO-CONH-N-methylpyridinium)[Ni(dmit)2]·CH3CN

Suppression of a Structural Phase Transition by an Orientational Disorder of Counteranions in an Organic Conductor, β″-β″-(BEDT-TTF)2ClC2H4SO3

In 2022, we reported that the β″-(BEDT-TTF)2ClC2H4SO3 salt (1) has a phase transition at 210 K on cooling and 260 K on heating, which was suggested as a nondoped-to-doped transition. During the synthesis of 1, a second salt was coproduced, the structure and properties of which are reported here. The new salt β″-β″-(BEDT-TTF)2ClC2H4SO3 (2) has the same composition and is isomorphous to 1L, the low-temperature phase of 1. However, the salt shows no phase transition. 1H, the high-temperature phase of 1, displays rotational disorders of the -SO3- groups. In contrast, the anions in 2 have no rotational disorders but have orientational disorders. Approximately 13% of the anions in 2 have their orientation as opposed to the remaining anions. The geometrically calculated shortest O···O distance is 2.24 Å if neighbor -SO3- groups are able to rotate freely. This is 1.1 Å shorter than the sum of the van der Waals radii, and therefore, this is too close to allow free rotation. Therefore, it is proposed that 2 has no rotational disorder, which leads to no phase transition as is observed in 1.

Structures and Properties of New Organic Molecule-Based Metals, (D)2BrC2H4SO3 [D = BEDT-TTF and BETS]

An organic anion, 2-bromoethanesulfonate (BrC2H4SO3−), provides one bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and two bis(ethylenedithio)tetraselenafulvalene (BETS) salts, the compositions of which are β’’-β’’-(BEDT-TTF)2BrC2H4SO3 (1), β’’-β’’-(BETS)2BrC2H4SO3 (2), and θ-(BETS)2BrC2H4SO3 (3), respectively. Compound 1 shows a metal–insulator transition at around 70 K. Compound 2 is isomorphous to 1, and 3 is polymorphic with 2. Compounds 2 and 3 show metallic behavior at least down to 4.2 K. The pressure dependence of the electrical resistivity of 1 is also reported.