  The assembly of complex structures is driven by an interplay between several
intermolecular interactions, from strong covalent bonds to weaker dispersion
forces. Surface-based self-assembly is particularly amenable to modeling and
measuring these interactions in well-defined systems. This study focuses on
2-butanol, the simplest aliphatic chiral alcohol. 2-butanol shows interesting
properties as a chiral modifier of surface chemistry, however, its mode of
action is not fully understood. In order to probe its surface properties we
employed high-resolution scanning tunneling microscopy and DFT simulations. We
found a surprisingly rich degree of enantiospecific adsorption, association,
chiral cluster growth and ultimately long range, highly ordered chiral
templating. Firstly, the chiral molecules acquire a second chiral center when
adsorbed to the surface via dative bonding of one of the oxygen atom lone
pairs. This interaction is controlled via the molecule's intrinsic chiral
center leading to monomers of like chirality, at both chiral centers, adsorbed
on the surface. The monomers then associate into tetramers via a cyclical
network of hydrogen bonds with an opposite chirality at the oxygen atom. The
evolution of these square units is surprising given that the underlying surface
has a hexagonal symmetry. Our DFT calculations reveal that the tetramers are
able to associate with each other by weaker van der Waals interactions and
tessellate in an extended square network. Our data reveals that the chirality
of a simple alcohol can be transferred to its surface binding geometry, drive
the directionality of hydrogen bonds and ultimately extended structure.
Furthermore, this study provides the first microscopic insight into the surface
properties of this important chiral modifier and provides a well-defined system
for studying the network's enantioselective interaction with other molecules.
