Architectural Diversity and Elastic Networks in Hydrogen-Bonded Host Frameworks: From Molecular Jaws to Cylinders

Guest-free guanidinium organomonosulfonates (GMS) and their inclusion compounds display a
variety of lamellar crystalline architectures distinguished by different “up−down” projections of the
organomonosulfonate residues on either side of a two-dimensional (2D) hydrogen-bonding network of
complementary guanidinium ions (G) and sulfonate moieties (S), the so-called GS sheet. Using a
combinatorial library of 24 GMS hosts and 26 guest molecules, a total of 304 inclusion compounds out of
a possible 624 possible host−guest combinations were realized, revealing a remarkable capacity of the
GMS hosts to form inclusion compounds despite the facile formation of the corresponding guest-free
compounds and the absence of “predestined” inclusion cavities like those in related guanidinium
organodisulfonate host frameworks. The GS sheets in the inclusion compounds behave as “molecular
jaws” in which organomonosulfonate groups projecting from opposing sheets clamp down on the guest
molecules, forming ordered interdigitated arrays of the host organic groups and guests. Both the guest-free and inclusion compounds display a variety of architectures that reveal the structural integrity of two-dimensional GS sheet and the unique ability of these hosts to conform to the steric demands of the organic
guests. Certain GMS host−guest combinations prompt formation of tubular inclusion compounds in which
the GS sheet curls into cylinders with retention of the 2D GS network. The cylinders assemble into hexagonal
arrays through interdigitation of the organosulfonate residues that project from their outer surfaces,
crystallizing in high-symmetry trigonal or hexagonal space groups. This unique example of network curvature
and structural isomerism between lamellar and cylindrical structures, with retention of supramolecular
connectivity, is reminiscent of the phase behavior observed in surfactant microstructures and block
copolymers. The large number of host−guest combinations explored here permits grouping of the inclusion
compound architectures according to the shape of the guests and the relative volumes of the organomonosulfonate groups, enabling more reliable structure prediction for this class of compounds than for
molecular crystals in general.