Heterocyclic 1,3-diazepine-based thiones and selones as versatile halogen-bond acceptors

Utilizing the N-heterocyclic chalcogenones hexahydro-1,3-bis(2,4,6-trimethylphenyl)-2H-1,3-diazepine-2-thione (SDiazMesS) and hexahydro-1,3-bis(2,4,6-trimethylphenyl)-2H-1,3-diazepine-2-selone (SDiazMesSe) as halogen-bond acceptors, a total of 24 new cocrystals were prepared. The solid-state structures of the parent molecules were also determined, along with those of their acetonitrile solvates. Through the reaction of the chalcogen atom with molecular diiodine, a variety of S—I—I and Se—I—I fragments were formed, spanning a wide range of I—I bond orders. With acetone as a reaction solvent, molecular diiodine causes the oxidative addition of acetone to the chalcogen atom, resulting in new C—S, C—Se and C—C covalent bonds under mild conditions. The common halogen-bond donors, iodopentafluorobenzene, 1,2-, 1,3- and 1,4-diiodotetrafluorobenzene, 1,3,5-trifluorotriiodobenzene and tetraiodoethylene resulted in halogen-bond-driven cocrystal formation. In most cases, the analogous SDiazMesS and SDiazMesSe cocrystals are isomorphic.