CT-adduct vs. pyridinium polyhalide salt formation in the reactions between polypyridyl donors and dihalogens: reactivity of 1,4-di-(3′-pyridylethynyl)benzene towards Br2 and I2

Abstract

The reactions of 1,4-di-(3′-pyridylethynyl)benzene (L) with I₂ and Br₂ in CH₂Cl₂ afforded 1 and 2, respectively: the former compound features CT-adduct units L·2I₂ connected by a third diiodine molecule to give (L·I₆)_∞ chains, while the latter is a salt where the monocation HL′⁺, derived from the N-protonation of a pyridine unit and dibromination of the triple C–C bonds of L, is counterbalanced by an asymmetric tribromide. The isolation of 1 and 2 provides a striking example of how the competition between the Lewis and Brønsted–Lowry basicity of polypyridyl donors can be exploited for the rational design of either neutral or charged building blocks of supramolecular architectures.