Tautomeric Equilibrium of an Asymmetric β-Diketone in Halogen-Bonded Cocrystals with Perfluorinated Iodobenzenes

In order to study the effect of halogen bond on tautomerism in β-diketones solid-state, we have prepared a series cocrystals derived from an asymmetric β-diketone, benzoyl-4-pyridoylmethane (b4pm), as acceptor and perfluorinated iodobenzenes: iodopentaflourobenzene (ipfb), 1,2-, 1,3- 1,4-diiodotetraflorobenzene (12tfib, 13tfib 14tfib) 1,3,5-triiodo-2,4,6-trifluorobenzene (135titfb). All five are assembled by I···N bonds involving pyridyl nitrogen iodoperfluorobenzene iodine resulting 1:1 (four compounds) or 1:2 (one compound) cocrystal stoichiometry. Tautomer b4pm which hydrogen atom is adjacent fragment was found be more stable vacuo than tautomer with benzoyl hydroxyl group. This also dominant majority crystal structures, somewhat abundantly structures additional I···O oxygen has been established. Attempts made prepare equivalent using closely related benzoyl-3-pyridoylmethane (b3pm); however, all attempts were unsuccessful, attributed effective packing b3pm isomer compared b4pm, reduced probability formation.