DECACYCLENE - A MOLECULAR PROPELLER WITH HELICAL CRYSTALS

The molecular structure of decacyclene was determined by X-ray analysi s of a single crystal grown by sublimation. The molecule is twisted in to a shallow molecular propeller due to nonbonded repulsions between h ydrogens of the peripheral naphthalene groups. Because decacyclene cry stallizes in the chiral space group C222(1) with Z = 4, the molecule l ies on a special position and all of the propellers have the same rela tive configuration. Interestingly, crystals of decacyclene also have a helical morphology which is most pronounced when grown from solutions in organic solvents. Powder X-ray diffraction studies on the solution -grown crystals (which are too small for single-crystal work) show the m to have the same unit cell, space group, and chiral crystal structur e. It is likely, though not proven, that left- and right-handed helica l crystals correspond to opposite enantiomers of the decacyclene prope ller.