Quasi-1D Cations ¹_∞[Ni₈Bi₈S]ⁿ⁺ of Variable Charge:  Infinite Columns ¹_∞[Ni₈Bi₈S]²⁺ in the Novel Compound Ni₈Bi₈SI₂

The new compound Ni₈Bi₈SI₂ has been synthesized and its crystal structure determined by X-ray crystallography. The structure contains one-dimensional (1D) cations ¹_∞[Ni₈Bi₈S]²⁺ separated by iodine anions. The geometry of the columns is similar to that of the recently reported ¹_∞[Ni₈Bi₈S]⁺, and the main difference between them is only their formal charge. Electronic structure calculations and physical properties measurements were performed to analyze the influence of the number of valence electrons on the bonding and properties of compounds containing these 1D cations. It was shown that the removal of one electron (i.e., ¹_∞[Ni₈Bi₈S]⁺ → ¹_∞[Ni₈Bi₈S]²⁺) mainly affects the Ni−S bonding within the cation and essentially has no influence on the intermetallic Ni−Bi bonding. It was found that Ni₈Bi₈SI₂ containing double-charged columns has conductivity properties more similar to a pure 1D metal than the congener Ni₈Bi₈SI containing mono-charged columns.