Combining Intra- and Intermolecular Charge Transfer with Polycationic Cyclophanes to Design 2D Tessellations

A series of donor-acceptor (D–A) naphthalene–viologen-based cyclophanes of different shapes, sizes and symmetries have been synthesized and characterized. Solution optical studies on these cyclophanes reveal the existence of photoinduced intramolecular charge transfer (CT) at 465 nm from naphthalene (D) to viologen (A) units, resulting in a conformational change in the viologen units and the emergence of an emission at 540 nm. The D–A cyclophanes with boxlike and hexagonlike shapes offer an opportunity to control the arrangement into 2D layers where D–A interactions direct the superstructures. While a boxlike 2,6-disubstituted naphthalene-based tetracationic cyclophane does not form square tiling patterns, a truncated hexagonlike congener self-assembles to form a hexagonal superstructure which, in turn, adopts a hexagonal-tiling pattern. Tessellation of the more rigid and highly symmetrical 2,7-disubstituted naphthalene-based cyclophanes leads to the formation of 2D square- and honeycomb-tiling patterns w...