An unprecedented non-classical polyinterhalogen anion made of [I2Cl]− and I2 at the 2-(p-tolyl)selenopheno[2,3-b]pyridinium cation template

Abstract

The reactivity between 2-(p-tolyl)selenopheno[2,3-b]pyridine (L) and ICl in MeCN is presented. Single crystal structure analysis revealed the formation of two distinct crystalline materials both featuring the protonated 2-(p-tolyl)selenopheno[2,3-b]pyridinium cation [HL]⁺. Colourless crystals were identified as the dihydrate salt [HL]Cl·2H₂O (1), and dark-red crystals as compound {[HL]⁺[I₂Cl]⁻}₃·1/2I₂ (2) that features the peculiar presence of the rare non-classical [I₂Cl]⁻ interhalide. Halogen Bonds (XBs) between the cocrystallized I₂ molecule and [I₂Cl]⁻ anions led to the novel overall discrete [I₁₀Cl₄]⁴⁻H-shaped polyinterhalide formation, which is stabilized through hydrogen bonds (HBs) with the templating [HL]⁺ cations. The experimental observations are supported by extensive theoretical calculations at the DFT level that were employed to study the role played by non-covalent interactions in the formation of the presented unique polyinterhalide.