Hal⋯Hal interactions in a series of three isostructural salts of halogenated tetrathiafulvalenes. Contribution of the halogen atoms to the HOMO–HOMO overlap interactions
作者:Benoît Domercq、Thomas Devic、Marc Fourmigué、Pascale AubanSenzier、Enric Canadell
DOI:10.1039/b100103p
日期:——
The halogenated tetrathiafulvalenes, Br2-EDT-TTF and I2-EDT-TTF were prepared by the coupling route from the corresponding 4,5-dibromo- or 4,5-diiodo-1,3-dithiole-2-thione. In the isostructural series, (Br2-EDT-TTF)2IBr2, (Br2-EDT-TTF)2I3 and (I2-EDT-TTF)2I3, noted Br2/IBr2, Br2/I3 and I2/I3 respectively, short (3.42â3.60Â Ã
) and directional Halâ¯Hal interactions are identified between donor molecules and with the anions, stabilising rare βⲠphases. These interactions play not only a structural role but also contribute to the electronic dispersion thanks to sizeable coefficients on the halogen atoms in the HOMOs of Br2-EDT-TTF and I2-EDT-TTF. The three salts
behave as Mott insulators as reflected by a high room temperature conductivity (0.5Â SÂ cmâ1) with an activation energy which increases in the order Br2/IBr2
(730Â K), Br2/I3
(1260Â K), I2/I3
(1330Â K) and a weak magnetic susceptibility, which decreases abruptly below 150Â K with no sign of an antiferromagnetic ground state.
卤化的四硫富瓦烯 Br2-EDT-TTF 和 I2-EDT-TTF 通过相应的 4,5-二溴或 4,5-二碘-1,3-二硫醇-2-酮的偶联途径制备。在同构系列中,(Br2-EDT-TTF)2IBr2、(Br2-EDT-TTF)2I3 和 (I2-EDT-TTF)2I3,分别记为 Br2/IBr2、Br2/I3 和 I2/I3,鉴定出短程(3.42–3.60 Å)且定向的卤-卤相互作用存在于供体分子与阴离子之间,从而稳定了稀有的 β′ 相。这些相互作用不仅发挥结构作用,还通过 Br2-EDT-TTF 和 I2-EDT-TTF 中 HOMOs 上卤素原子的显著系数对电子分散产生贡献。这三种盐表现出莫特绝缘体特性,其高室温电导率(0.5 S cm⁻¹)反映出其活化能按 Br2/IBr2 (730 K)、Br2/I3 (1260 K) 和 I2/I3 (1330 K) 的顺序增加,且具有较弱的磁化率,在 150 K 以下急剧下降,未出现反铁磁基态的迹象。