Synthesis, structure and charge state of the 1:4 molecular conductor (n-Bu4N)[Ni(dmit)2]4·MeCN

Abstract

In a tetrad {[Ni1][Ni2][Ni3][Ni4]} − , the HOMO electron’s home is at [Ni2] and the electron can leave to visit its neighbors [Ni1] [Ni3], but rarely go to [Ni4]. A new molecular conductor ( n -Bu 4 N)[Ni(dmit) 2 ] 4 ·MeCN (dmit = 2-thioxo-1,3-dithiole-4,5-dithiolato) has been synthesized and its X-ray structure has been determined. The crystal exhibits conductivity 0.1 Ω −1 cm −1 at room temperature and a semi-conducting behavior with small activation energy of 0.170 eV (at 295 K) and 0.065 eV (at 95 K). The coordination anions are arranged in a parallel fashion in the crystal forming two-dimensional networks, in which the face-to-face π – π longitudinal intermolecular interactions are stronger than the side-by-side S⋯S transverse interactions. The anionic stacks along the b -direction exhibit a type of tetrad structure. Infrared spectra suggest that the tetrad {4[Ni(dmit) 2 ]} − may consist of one mono-anion [Ni(dmit) 2 ] − and three neutral [Ni(dmit) 2 ] units. The bond analysis further suggests that the single electron in the HOMO of [Ni(dmit) 2 ] − can delocalize to its two neighboring [Ni(dmit) 2 ] molecules to some extent.