Lamellae-Nanotube Isomerism in Hydrogen-Bonded Host Frameworks This work was supported by the National Science Foundation (DMR-9908627), in part by the MRSEC Program of the National Science Foundation (DMR-9809364), and the Natural Sciences and Engineering Research Council of Canada (postdoctoral fellowship for K.T.H.).

Inclusion compounds based on a flexible hydrogen-bonded sheet of guanidinium ions and sulfonate moieties display lamellar and tubular architectures, depending on the guest and the organic substituent attached to the sulfonate. The observed single-crystal architectures resemble lamellar and hexagonal microstructures in block copolymers and surfactant assemblies.