Tetrathiafulvalene-, 1,5-dioxynaphthalene-, and cyclobis(paraquat-p-phenylene)-based [2]rotaxanes with cyclohexyl and alkyl chains as spacers:: Synthesis, Langmuir-Blodgett films, and electrical bistability

The synthesis and characterization of two new (TTF-DNP-CBPQT(4+)) [2]rotaxanes 1 and 2 is reported, based on tetrathiafulvalene (TTF), 1,5-dioxynaphthalene (DNP), and cyclobis(paraquat-p-phenylene) (CBPQT 4,) with cyclohexyl and alkyl chains as the spacers. Multilayer Langmuir-Blodgett (LB) films of [2]rotaxanes 1 and 2 are prepared. Conducting atomic force microscopy, scanning tunneling microscopy, and two-terminal junction device studies indicate that the LB films of [2]rotaxanes 1 and 2 show electrical bistability behavior. By comparing with the TTF-DNP-CBPQT 41 [2]rotaxanes reported by Stoddart et al. previously, the present results imply that proper modification of the chemical structures of the TTF unit and the spacer have negligible effect on the electrical bistability behavior of these TTF-DNP-CBPQT 41 [2]rotaxanes. These findings will allow for the design and preparation of new multifunctional TTF-DNP-CBPQT 4, [2]rotaxanes in the future.