Cyclotris(paraquat-p-phenylenes)

Abstract

Reported here is the synthesis, solid-state characterization, and redox properties of new triangular, threefold symmetric, viologen-containing macrocycles. Cyclotris(paraquat-p-phenylene) (CTPQT⁶⁺ ) and cyclotris(paraquat-p-1,4-dimethoxyphenylene) (MCTPQT⁶⁺ ) were prepared and their X-ray single-crystal (super)structures reveal intricate three-dimensional packing. MCTPQT⁶⁺ results in nanometer-sized channels, in contrast with its parent counterpart CTPQT⁶⁺ which crystallizes as a couple of polymorphs in the form of intercalated assemblies. In the solid state, MCTPQT^3(.+) exhibits stacks between the 1,4-dimethoxyphenylene and bipyridinium radical cations, providing new opportunities for the manipulation and control of the recognition motif associated with viologen radical cations. These redox-active cyclophanes demonstrate that geometry-matching and weak intermolecular interactions are of paramount importance in dictating the formation of their intricate solid-state superstructures.

Keywords: macrocycles; nanoporous materials; radicals; self-assembly; solid-state structures.