title: Structural effects on the solid-state photodimerization of 2-pyridone derivatives in inclusion compounds.
abstract: The structures of six crystalline inclusion compounds between various host molecules and three guest molecules based on the 2-pyridone skeleton are described. The six compounds are 1,1'-biphenyl-2,2'-dicarboxylic acid-2-pyridone (1/2), C(14)H(10)O(4).2C(5)H(5)NO, (I-a), 1,1'-biphenyl-2,2'-dicarboxylic acid-4-methyl-2-pyridone (1/2), C(14)H(10)O(4).2C(6)H(7)NO, (I-c), 1,1'-biphenyl-2,2'-dicarboxylic acid-6-methyl-2-pyridone (1/2), C(14)H(10)O(4).2C(6)H(7)NO, (I-d), 1,1,6,6-tetraphenyl-2,4-hexadiyne-1,6-diol-1-methyl-2-pyridone (1/2), C(30)H(22)O(2).2C(6)H(7)NO, (II-b), 1,1,6,6-tetraphenyl-2,4-hexadiyne-1,6-diol-4-methy-2-pyridone (1/2), C(30)H(22)O(2).2C(6)H(7)NO, (II-c), and 4,4',4''-(ethane-1,1,1-triyl)triphenol-6-methyl-2-pyridone-water (1/3/1), C(20)H(18)O(3).3C(6)H(7)NO.H(2)O, (III-d). In two of the compounds, (I-a) and (I-d), the host molecules lie about crystallographic twofold axes. In two other compounds, (II-b) and (II-c), the host molecules lie across inversion centers. In all cases, the guest molecules are hydrogen bonded to the host molecules through O-H...O=C hydrogen bonds [the range of O...O distances is 2.543 (2)-2.843 (2) A. The pyridone moieties form dimers through N-H...O=C hydrogen bonds in five of the compounds [the range of N...O distances is 2.763 (2)-2.968 (2) A]. In four compounds, (I-a), (I-c), (I-d) and (II-c), the molecules are arranged in extended zigzag chains formed via host-guest hydrogen bonding. In five of the compounds, the guest molecules are arranged in parallel pairs on top of each other, related by inversion centers. However, none of these compounds underwent photodimerization in the solid state upon irradiation. In one of the crystalline compounds, (III-d), the guest molecules are arranged in stacks with one disordered molecule. The unsuccessful dimerization is attributed to the large interatomic distances between the potentially reactive atoms [the range of distances is 4.027 (4)-4.865 (4) A] and to the bad overlap, expressed by the lateral shift between the orbitals of these atoms [the range of the shifts from perfect overlap is 1.727 (4)-3.324 (4) A]. The bad overlap and large distances between potentially photoreactive atoms are attributed to the hydrogen-bonding schemes, because the interactions involved in hydrogen bonding are stronger than those in pi-pi interactions.
authors: Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa, 32000, Israel.
authors: Marina
authors: M
authors: Telzhensky
authors: Menahem
authors: M
authors: Kaftory