In Situ Imaging of On-Surface, Solvent-Free Molecular Single-Crystal Growth

The formation of crystalline materials
has been studied for more
than a century. Recent discoveries about the self-assembly of many
inorganic materials, involving aggregation of nanoparticle (NP) precursors
or pre-nucleation clusters, challenge the simple assumptions of classical
crystallization theory. The situation for organic materials is even
more of a terra incognita due to their high complexity. Using in situ
high-temperature atomic force microscopy during the solvent-free crystallization
of an organic compound [Ni­(quinolone-8-thiolate)2], we
observe long-range migration of NPs on a silica substrate and their
incorporation into larger crystals, suggesting a non-classical pathway
in the growth of the molecular crystal.