Dynamic control over supramolecular handedness by selecting chiral induction pathways at the solution–solid interface

A dominant theme within the research on two-dimensional chirality is the sergeant–soldiers principle, wherein a small fraction of chiral molecules (sergeants) is used to skew the handedness of achiral molecules (soldiers) to generate a homochiral surface. Here, we have combined the sergeant–soldiers principle with temperature-dependent molecular self-assembly to unravel a peculiar chiral amplification mechanism at the solution–solid interface in which, depending on the concentration of a sergeant–soldiers solution, the majority handedness of the system can either be amplified or entirely reversed after an annealing step, furnishing a homochiral surface. Two discrete pathways that affect different stages of two-dimensional crystal growth are invoked for rationalizing this phenomenon and we present a set of experiments where the access to each pathway can be precisely controlled. These results demonstrate that a detailed understanding of subtle intermolecular and interfacial interactions can be used to induce drastic changes in the handedness of a supramolecular network. The formation of homochiral supramolecular networks at solution–solid interfaces typically relies on the soldier-and-sergeant approach, in which a small amount of chiral modifier defines the handedness of the network. Now, judicious choice of the sergeant, solvent, temperature and concentration has enabled chiral induction pathways to be controlled so that a homochiral surface of either handedness can be assembled from the same system.