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.