engleski

Preservation of pyridone homosynthon in halogen- bonded cocrystals

It is well known that species containing 2- pyridone (pdon) fragment easily undergo tautomerization process which includes two tautomeric forms – lactame and lactime.[1] In solid state, both tautomers can aggregate in robust hydrogen-bonded dimers (pdon)2 by pyridone homosynthon involving two N–H···O or O–H···N hydrogen bonds.[2] Constancy of such dimers is noticed in systems with carboxylic diacids (CA), [3] in which (pdon)2 fragments are linked with CA molecules into alternating O–H···O hydrogen-bonded chains through keto oxygen atom. However, coexistence of pdon dimers with halogen bond donors in crystals has not been noticed to date. To investigate hierarchy of supramolecular interactions in systems including pdon and halogen bond donors, we synthesized a series of cocrystals of 2-pyridone and six perhalogenated hydrocarbons (1 monotopic and 5 ditopic donors). In all prepared compounds, 2-pyridone is present in lactame form and expectedly connected in centrosymmetric dimers through two N– H···O hydrogen bonds. Halogen bond donor molecules participate in I···O halogen bonding with (pdon)2 fragments, while cocrystal stoichiometry is conditioned by donor topicity: 1:1 cocrystal is formed with monotopic donor, while 2:1 with ditopic donors. In former case molecules are connected in discrete complexes, while in the latter, supramolecular chains have formed.

halogen bond, hydrogen bond, synthon, piridone

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