Chiral Mechanically Interlocked Molecules – Applications of Rotaxanes, Catenanes and Molecular Knots in Stereoselective Chemosensing and Catalysis

Abstract

Interlocked molecules, such as rotaxanes, catenanes, and molecular knots, offer conceptually new possibilities for the generation of chiral chemosensors and catalysts. Due to the presence of the mechanical or topological bond, interlocked molecules can be used to design functional systems with unprecedented features, such as switchability and deep binding cavities. In addition, classical elements of chirality can be supplemented with mechanical or topological chirality, which have so far only scarcely been employed as sources of chirality for stereoselective applications. This minireview discusses recent examples in this emerging area, showing that the application of chiral interlocked molecules in sensing and catalysis offers many fascinating opportunities for future research.1 Introduction2 Interlocked Molecules with Chiral Subcomponents2.1 Point Chirality2.2 Axial Chirality3 Mechanically Chiral Interlocked Molecules4 Topologically Chiral Interlocked Molecules5 Outlook

Chiroptical inversion of a planar chiral redox-switchable rotaxane

“…13 Chiral rotaxanes may be chiral from inclusion of classical stereogenic elements or by virtue of being mechanically planar chiral. Since then, several examples followed, [14][15][16][17][18][19][20][21][22][23][24][25] in which the mechanically interlocked structure was used to induce directionality in polymers, [26][27][28] for sensing, [29][30][31] and to act as an enantioselective catalyst. 32 Today, sophisticated synthetic protocols allow an efficient enantioselective synthesis.…”

Stereoselective Synthesis of Molecular Square and Granny Knots

“…Most of the small-molecule knots 1 synthesized to date are trefoil 2 (3 1 ) 3 knots, the simplest nontrivial knot topology. The few examples of more complex synthetic molecular knots 4,5 are highly symmetrical, 6 with the strand crossings assembled in one or two steps using frameworks designed to only tolerate the particular crossing pattern required.…”

A Chiral Interlocking Auxiliary Strategy for the Synthesis of Mechanically Planar Chiral Rotaxanes

“…In principle, our approach is not limited to the AT-CuAAC synthesis of rotaxanes; it should be possible to extend the chiral interlocking auxiliary concept to other mechanical bond forming approaches using simply by identifying a chiral unit that gives rise to diastereoselective mechanical bond formation and from which the macrocycle can be shuttled away. Given recent reports of applications of mechanically chiral molecules, 10,17,34,35 and the increasing interest in the applications of chiral interlocked molecules in general, 36,37,38,39,40,41 we anticipate that these findings will spur further progress in the development of mechanically chiral systems.…”