Abstract
This update reviews the major developments on rotaxane-based shuttles during the period of August 2008 to October 2010 and is organized similarly to the previous review [1].
The progress in the field of chemical controlled shuttles can be summarized as a significant increase of the shuttling rates, second-generation pH-switchable Pd(II)-complexed rotaxanes, and new synthetic approaches, especially those based on Diels-Alder cycloadditions. The new synthetic routes allow ready access to rotaxanes that feature the template site fully incorporated into the interlocked product. This template site is unusual for active-template reactions and produces shuttles that exhibit entropy-driven translational isomerism with remarkably improved positional discrimination as was shown by the incorporation of a hydrogen-bonding TEG-station into an imine-bridged rotaxane.
With respect to photochemically powered molecular switches, the most important result originated from the synthesis of a degenerate, donor-acceptor, light-gated, STOP-GO molecular shuttle. For electrochemically controllable bistable rotaxanes, the first example of a molecular shuttle with three different stations, which dramatically increase the shuttling process rate, has been reported.
Finally, the last study in this review involves redox-driven switching and electrochromic responses of LC films containing a bistable [2]rotaxane. The presence of a polymer electrolyte provides new prospects for the further development of rotaxane-based molecular materials by exploiting the dynamic, anisotropic, and coherent properties of liquid crystals.
Keywords: Mechanically interlocked molecules, Click chemistry, Molecular devices, Nanoscale machines, Rotaxane-Based, Shuttles, interlocked machines, chemically, photochemically, electrochemically, induced molecular, ring component, molecules, synthetic methodologies, kinetics
Call for Papers in Thematic Issues
Catalytic C-H bond activation as a tool for functionalization of heterocycles
The major topic is the functionalization of heterocycles through catalyzed C-H bond activation. The strategies based on C-H activation not only provide straightforward formation of C-C or C-X bonds but, more importantly, allow for the avoidance of pre-functionalization of one or two of the cross-coupling partners. The beneficial impact of ...read more
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