Hierarchical iodine(i) complexes of nicotinamide

Abstract

The incorporation of the 3-substituted pyridine derivative nicotinamide (1) into an iodine(I) complex gave the hierarchical iodine(I) complex, [I(nicotinamide)₂]PF₆ (3), synthesised through cation exchange with I₂ of the respective silver(I) complex, [Ag(nicotinamide)₂]PF₆ (2). Complex 3 was characterised in both solution (¹H, ¹H–¹⁵N HMBC), and extensively in the solid state by single-crystal X-ray diffraction (SCXRD) due to the various polymorphs and solvates observed. As only the second example of a hierarchical halogen(I) complex, analysis of the different hydrogen-bonding networks present in the solid-state variants of 3 allowed the relationship between the halogen and hydrogen bonding to be explored in more depth. The presence of the hydrogen bonds in the non-solvated solid-state structure of 3 (3_NS) was found to impart increased resilience to H₂O and acetic acid, all without diminishing its reactivity as an iodination reagent in comparison to Barluenga's reagent ([I(pyridine)₂]BF₄), as demonstrated via solution and mechanochemical reactivity studies with antipyrine.