Syntheses and characterization of 5-substituted hydantoins and thiazolines - implications for crystal engineering of hydrogen bonded assemblies. Crystal structures of 5-(2-pyridylmethylene)hydantoin, 5-(2-pyridylmethylene)-2-thiohydantoin, 5-(2-pyridylmethylene)thiazolidine-2,4-dione, 5-(2-pyridylmethylene)rhodanine and 5-(2-pyridylmethylene)pseudothiohydantoin

A series of six potentially bidentate ligands composed of 5-membered heterocyclic rings with methylenepyridyl substituents are described. These molecules are potentially bifunctional, acting as bidentate ligands to metal centres whilst retaining on their periphery a range of groups capable of forming triple hydrogen bonds. Their metal complexes have the potential to display interesting magnetic, optical and electrochemical properties when the hydrogen bonds are used for the crystal engineering of solid state materials. Here we report the synthesis and characterization of the six closely related molecules, 5-(2-pyridylmethylene)hydantoin I, 5-(2-pyridylmethylene)-2-thiohydantoin II, 5-(2-pyridylmethylene)thiazolidine-2,4-dione III, 5-(2-pyridylmethylene)rhodanine IV, 5-(2-pyridylmethylene)pseudothiohydantoin V and 5-(2-pyridylmethylene)-2-imino-4-amino-2,5-dihydrothiazole VI. The solid state structures of I-VI have been studied using natural abundance solid state N-15 NMR spectroscopy and the single crystal structures of I-V are discussed.