Lamellar twinning explains the nearly racemic composition of chiral, single crystals of hexahelicene

Solvent etching of single crystals of hexahelicene grown from a racemic solution reveals an unusual layer-like pattern in which pure (+)- and pure (-)-layers alternate through the crystal; this arrangement results in a nearly racemic composition although the crystal is ostensibly chiral, space group P2₁2₁2₁. Etched crystals of enantiomerically pure hexahelicene display no such pattern. The two kinds of crystal are indistinguishable by x-ray diffraction.