Synthesis, X-ray characterization and study of new ionic complexes of 2-pyridone, obtained by oxidation with I2

The reaction of 2-pyridone (C5H5NO or PYOH) with diiodine in molar ratios of 2 : 1 and 1 : 2 resulted in the formation of complexes {[(PYOH)(3)(PYOH)(+)]center dot I-3(-)} (1) and {{(PYOH)(6)center dot[(PYOH)(2)](2+)}center dot 0.5I(-)center dot 1.5I(7)(-)center dot I-2} (2), respectively. The reactions were carried out in dichloromethane solutions in air. The compounds were characterized by elemental analysis, DTA-TGA chromatography, FT-Raman, FT-IR, UV-vis and EPR spectroscopies. Crystal structures of the named complexes have been determined by X-ray diffraction at 120(1) K (1) and 293(2) K (2). Compound 1, [(C20H20N4O4)I-3], monoclinic, space group C2/c, consists of a cationic PYOH+ radical species and an I-3(-) counter anion; three neutral PYOH molecules are also bound to the complex. The crystal structure of [(C40H40N8O8)I-13] (2) reveals a centrosymmetric P-1 triclinic space group containing two cationic PYOH+ species, with the anionic counterparts being one half I- and three halves I-7(-). Also, a neutral diiodine molecule I-2 is retained by weak halogen-halogen interactions to I-, as well as six neutral PYOH ligands. The structures of 1 and 2 consist of hydrogen-bonded pyridine layers; polyiodide fragments fill the spaces between the layers, additionally kept together by a number of weak C-H center dot center dot center dot I interactions.