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, MCTPQT3(.+) 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.

Electron‐Rich, Lewis Acidic Diborane Meets N‐Heterocyclic Aromatics: Formation and Electron Transfer in Cyclophane Boranes

“…Figure a shows the Lewis representations of some literature‐known examples of viologen cyclophanes with aromatic or flexible alkyl linkers, cyclobis(paraquat‐ p ‐phenylene) (CBPQT 4+ ), cyclobis(paraquat‐ p ‐biphenylene) (CBPQTBP 4+ ), and ExBox 4+ , a box‐like cyclophane comprising two 4,4’‐phenylene‐linked „extended“ bipyridinium units . Very recently, first cyclotris(paraquat‐ p ‐phenylenes) were synthesized . Cyclophanes with 1,2‐bis(4‐pyridyl)ethylene units, that could be photoisomerized, were also reported .…”