IntroductionThe helical tubuland hosts are a group of chiral alicyclic dialcohols (such as1–4inChart 1) which crystallise in space groupP3121 (or enantiomorphP3221) as a hydrogen bonded network structure containing parallel tubes filled with guest molecules.1–3These compounds are noteworthy for several reasons, one being that new members of the family can be designed by following a set of molecular structure and symmetry rules.4Furthermore, since only one enantiomer of the dialcohol can be accommodated in the crystal lattice, a conglomerate5,6is produced each time that one of these racemic dialcohols produces a helical tubulate inclusion compound. In other words, spontaneous self-resolution occursto yield a 1∶1 mixture of pure (+)- and pure (−)-crystals. Indeed, these compounds are remarkable for exhibiting this phenomenon so reliably.7Molecular structures of four typical members1–4of the helical tubuland host family. Only one enantiomer of each chiral dialcohol is represented here.Racemic dialcohol2is somewhat of a rogue substance amongst this otherwise well-behaved family of compounds. Unlike the other dialcohol hosts it can form two very different types of lattice inclusion structures. The ellipsoidal clathrate lattice is constructed from two identical, but inversion-related, interpenetrating sub-lattices of 4284net topology.8Compounds of stoichiometry (2)4·(guest) are formed in the tetragonal space groupI41/acdand both enantiomers of2are present in each hydrogen bonded sub-lattice. Rugby ball-shaped cavities located between the two interpenetrating sub-lattices contain the trapped guest molecules.9The alternative helical tubulate lattice contains the guest molecules within parallel molecular tubes. Crystals of stoichiometry (2)3·(guest)x, where the host and guest arrangements need not be commensurate, are produced in the enantiomorphous trigonal space groupsP3121 orP3221.10Which lattice type is formed depends principally on the size and shape of the guests, and hence the structures can be predicted in advance with a good degree of certainty.1Smaller11guest molecules, for example dichloromethane or cyclohexane, yield the ellipsoidal clathrate lattice as these guests can be accommodated within the rugby ball-shaped cavities of the host lattice. Slightly larger11guests, such as chloroform or fluorocyclohexane, can no longer fit and thus are included as helical tubulates instead.For some time we have been interested in learning what would occur if the racemic samples of dialcohol2were replaced by chirally pure material. This communication explores some of these outcomes.