(α-DT-TTF)₂[Au(mnt)₂]: A Weakly Disordered Molecular Spin-Ladder System

Abstract

The synthesis and characterization of (α-DT-TTF)2[Au(mnt)2] is reported. The magnetic properties of this new salt show that it is still a rare example of an organic spin-ladder. (α-DT-TTF)2[Au(mnt)2] shares the same ladder structure of the DT-TTF and ETT-TTF analogues, and its room temperature conductivity is ∼2 S/cm. Despite the observed donor orientation disorder associated with the thiophenic sulfur atoms, the intermolecular interactions between donor units, calculated using the extended Hückel approximation and a double-ξ basis set, show that the interaction values do not depend on the configuration of the sulfur atom on the thiophenic ring. The insensitivity of the spin-ladder magnetic properties to the donor molecular disorder in (α-DT-TTF)2[Au(mnt)2] is a direct consequence of the negligible contribution of the disordered thiophenic sulfur atom to the HOMO. In the related donor ETT-TTF, this contribution is significant and destroys the magnetic interactions, and no spin-ladder is observed. This compound not only enlarges the number of organic spin-ladder systems in this series of closely related compounds but also provides an interesting example of weakly disordered molecular spin-ladder system.

Charge‐Transfer Salts Based on a Dissymmetrical Cyano‐Substituted Tetrathiafulvalene Donor

“…The Ni-S (2.144, 2.143 Å) and Au-S bond lengths (2.312, 2.313 Å; see Table S1) are typical of monoanionic [M(mnt) 2 ] -complexes with M = Ni [5] and Au [6] and identical to those found in related salts. [7] As expected, the donor bond lengths, namely, the central C=C and C-S bonds, which in TTF-type donors are more sensitive to the oxidation state, [8] were intermediate between those of the neutral donor [1] and the fully oxidized donors in salt 3 (see below and Table S2). …”

A Methyl‐Substituted Thiophene–Tetra­thiafulvalene Donor and Its Salts

“…[5] The electronic mobility and the possibility to use this donor as a semiconductor was evaluated in OFET devices. The OFET structures were fabricated on Si/SiO 2 substrates with an interdigitated structure of gold contacts.…”

“…[4] In spite of a similar orientation disorder, a spin-ladder magnetic system was found in α-DT-TTF salts, which behave as weakly disordered spin-ladder systems. [5] These electronic donors based on thiophene-moiety-fused tetrathiafulvalene have also attracted considerable interest as active materials in organic field-effect transistors. [6] A very high mobility of up to 6.2 cm 2 V -1 s -1 .…”

“…[8] Lower mobilities have been observed in α-DT-TTF having a different structure with less extended interactions. [5] Therefore, it seems of clear interest to explore similar donors with different substituent groups and to see how the physical properties are changed by the possible structural differences induced by these substituents. With such an aim, we selected α-methyldithiophene-tetrathiafulvalene (α-mDT-TTF, 1), a substituted α-DT-TTF derivative with a methyl group, [9] which was expected to modulate the packing pattern of the donor molecules in the solid state.…”

Correlating conduction properties with the molecular symmetry: segregation of Z and E isomers in the charge-assisted, halogen-bonded cocrystal [(Z,E)-Me2I2TTF]2Br

“…10 Furthermore, upon oxidation to the radical cation, the central C=C bond is weakened, favoring also the Z-E isomerism. 11 As a consequence, the salts of Form C TTFs such as BET-TTF or -DT-TTF are most often found, either as a mixture of Z and E isomers disordered on one single position (hence an averaged Form A D 2h symmetry), 12,13 or as a pure centrosymmetric E isomer known to favor more compact structures (see Tables S1-S3). …”