The Generality of Architectural Isomerism in Designer Inclusion Frameworks

We describe herein new structural isomers of a lamellar host system based on organodisulfonate
“pillars” that connect opposing hydrogen-bonded sheets, consisting of topologically complementary guanidinium
(G) ions and sulfonate (S) groups, to generate inclusion cavities between the sheets. These new isomerszigzag brick, double brick, V-brick, and crisscross bilayerexpand significantly on our earlier report of
architectural isomerism displayed by the discrete bilayer and simple brick forms. We demonstrate here that
the discrete bilayer−simple brick isomerism, which was limited to several host−guest combinations based on
the G2(4,4‘-biphenyldisulfonate) host and one pair of compounds based on the G2(2,6-naphthalenedisulfonate),
can be generalized to other organodisulfonate pillars. Furthermore, in many cases the selectivity toward the
different framework isomers reflects a rather systematic templating role of the guest molecules and host−guest recognition during assembly of the lattice. We also describe a convenient approach to identifying and
classifying the innumerable possible host architectures based upon the pillar projection topologies for the GS
sheets and the intersheet connectivities. The discovery of these new architectures reveals a structural versatility
for this class of materials that exceeds initial expectations and observations. Each topology produces different
connectivities between the sheets in the third dimension that endows each framework isomer with uniquely
shaped and sized inclusion cavities, enabling this host system to conform readily to different guests. The
unlimited number of architectures available, combined with the inherent conformational softness and structural
tunability of these host lattices, suggests a near universality for the GS system with respect to guest inclusion.