New sterically driven mode for generation of helical chirality.

The presented results and the available literature data convincingly suggest that there is a new sterically driven mechanism for the formation of supramolecular helicity in the solid state. This mechanism requires the presence of sterically bulky groups, such as tert-butyl, for which the spiral arrangement in uninterrupted hydrogen-bonding chains, serving as an axis for helical structure and maximizing the repulsive stereochemical interactions, provide for the most efficient, spatially economical accommodation of these groups in a crystallographic unit cell.