Multifunctional Tricarbazolo Triazolophane Macrocycles: One-Pot Preparation, Anion Binding, and Hierarchical Self-Organization of Multilayers

Programming the synthesis and self-assembly of molecules is a compelling strategy for the bottom-up fabrication of ordered materials. To this end, shape-persistent macrocycles were designed with alternating carbazoles and triazoles to program a one-pot synthesis and to bind large anions. The macrocycles bind anions that were once considered too weak to be coordinated, such as PF6 (-) , with surprisingly high affinities (β2 =10(11)  M(-2) in 80:20 chloroform/methanol) and positive cooperativity, α=(4 K2 /K1 )=1200. We also discovered that the macrocycles assemble into ultrathin films of hierarchically ordered tubes on graphite surfaces. The remarkable surface-templated self-assembly properties, as was observed by using scanning tunneling microscopy, are attributed to the complementary pairing of alternating triazoles and carbazoles inscribed into both the co-facial and edge-sharing seams that exist between shape-persistent macrocycles. The multilayer assembly is also consistent with the high degree of molecular self-association observed in solution, with self-association constants of K=300 000 M(-1) (chloroform/methanol 80:20). Scanning tunneling microscopy data also showed that surface assemblies readily sequester iodide anions from solution, modulating their assembly. This multifunctional macrocycle provides a foundation for materials composed of hierarchically organized and nanotubular self-assemblies.

Publication year:2016