Regulating the Architectures of Hydrogen-Bonded Frameworks through Topological Enforcement

The role of conformational flexibility in topological enforcement
of several crystalline materials based on hydrogen-bonded two-dimensional
guanidinium-sulfonate (GS) networks is demonstrated by using a series
of organopolysulfonates that prompt the formation of either lamellar
or cylindrical architectures. Whereas flexible organopolysulfonate
linkers decorated with flexible arms self-assemble into lamellar architectures,
rigid organopolysulfonates linkers enforce the formation of hydrogen-bonded
cylinders with intercylinder spacing governed by the size of the linker.
Specifically, hexagonal cylindrical structures generated from trisulfonates
with three-fold molecular symmetry are the topological equivalent
of the cylindrical hexagonal phases reported previously for guanidinium
organomonosulfonate inclusion compounds, but neighboring cylinders
are now connected through covalent nodes provided by the trisulfonates
rather than dispersive interactions between the arene rings of the
organomonosulfonates. Organopolysulfonates with moderate conformational
freedom, however, can generate both lamellar and cylindrical structures,
depending on the guest molecules encapsulated by the host framework.
These observations illustrate that the crystal architecture (i.e.,
lamellar vs cylindrical) and the shape of GS cylinders can be regulated
in a predictable way by the molecular symmetries and conformational
constraints of the organopolysulfonates building blocks.