An Iodine-Vapour-Induced Cyclization in a Crystalline Molecular Flask

A vapour-induced cyclisation has been demonstrated in the hosted environment of a crystalline molecular flask (CMF), within which 1,8-bis(2-phenylethynyl)naphthalene (bpen), a diarenynyl system primed for cyclisation, has been exposed to iodine vapour to yield the corresponding indeno[2,1-α]phenalene species. The cyclisation process, unique in its vapour-induced, solvent-free nature, has been followed spectroscopically, and found to occur concurrently with the displacement of lattice solvent for molecular iodine in CMF·0.75bpen·2.25CHCl3·H2O. The cyclisation occurs under mild conditions and without the need to suspend the crystals in solvent. The ability of CMFs to host purely gas-induced reactions is further highlighted by a subsequent, sequential, oxidation reaction of the cyclised 7-iodo-12-phenylindeno[2,1-α]phenalene (ipp) with molecular oxygen derived from air, yielding 12-hydroxy-7-iodo-2-phenylindeno[2,1-α]phenalen-1(12H)-one (hipp).