Structural organization and dimensionality at the hands of weak intermolecular Au⋯Au, Au⋯X and X⋯X (X = Cl, Br, I) interactions

Abstract

The salts K[AuCl₂(CN)₂]·H₂O (1), K[AuBr₂(CN)₂]·2H₂O (2) and K[AuI₂(CN)₂]·⅓H₂O (3) were synthesized and structurally characterized. Compound 1 crystallizes as a network of square planar [AuCl₂(CN)₂]⁻ anions separated by K⁺ cations. However, 2 and 3 feature 2-D sheets built by the aggregation of [AuX₂(CN)₂]⁻ anions via weak, intermolecular X⋯X interactions. The mixed anion double salts K₃[Au(CN)₂]₂[AuBr₂(CN)₂]·H₂O (4) and K₅[Au(CN)₂]₄[AuI₂(CN)₂]·2H₂O (5) were also synthesized by cocrystallization of K[Au(CN)₂] and the respective K[AuX₂(CN)₂] salts. Similarly to 2 and 3, the [Au(CN)₂]⁻ and [AuX₂(CN)₂]⁻ anions form 2-D sheets via weak, intermolecular Au^I⋯X and Au^I⋯Au^I interactions. In the case of 5, a rare unsupported Au^I⋯Au^III interaction of 3.5796(5) Å is also seen between the two anionic units. Despite the presence of Au(I) aurophilic interactions of 3.24–3.45 Å, neither 4 nor 5 exhibit any detectable emission at room temperature, suggesting that the presence of Au^I⋯X or Au^I⋯Au^III interactions may affect the emissive properties.