Recent Advances in the Synthesis and Application of Hydrogen Bond Templated Rotaxanes and Catenanes

Abstract

Alongside the use of metal cations and π–π stacking, hydrogen bonding is one of the major templating interactions used to prepare rotaxanes and catenanes. In this review, a brief summary of key historical milestones will be followed by discussion of developments from over the last decade in both synthetic methodology and application of hydrogen bond templated interlocked molecules. Hydrogen bond templation can allow for rapid access to interlocked molecules in high yields, with select examples having been put to useful purpose, in applications such as organocatalysis and cellular imaging.

Weak functional group interactions revealed through metal-free active template rotaxane synthesis

“…In principle the enforced high local concentration of convergent functional groups brought about by such mechanical bonding can stabilize weak non-covalent interactions 4 . In practice such outcomes are rarely observed [4][5][6][7][8] because most rotaxane syntheses rely upon strong attractive interactions between the building blocks 2,3,[9][10][11][12][13] to promote the rotaxane assembly process. Strong binding modes generally 'live on' in the interlocked product, an outcome useful for the design of artificial molecular machinery 2,3,[14][15][16] , whether intended to operate in solution 17 or when organized on surfaces 18,19 or within metal-organic frameworks 20,21 , but one that tends to override alternative weaker binding modes that could occur between the components.…”

Regulation of Macrocycle Shuttling Rates in [2]Rotaxanes by Amino‐Acid Speed Bumps in Organic–Aqueous Solvent Mixtures

“…Indeed a variety of effective methods for the synthesis of rotaxanes has been established through numerous synthetic strategies . Among a wide diversity of reported interlocked structures, molecular shuttles comprising a mobile macrocycle threaded on a two‐station axle, is one of the most emblematic types of architecture, which serves as an excellent platform for bottom‐up studies of dynamic properties . With sub‐molecular movement being integral to potential function in molecular machines, regulation of dynamics, both spontaneous and stimulus‐induced, is essential and intimately linked with molecular design .…”

Lanthanide‐Containing Rotaxanes, Catenanes, and Knots

“…[11] The opportunities offered in the construction of molecular machines by the relative motion of the constituent parts of rotaxanes and catenanes has been recognized by the award of the 2016 Nobel Prize in Chemistry. [12] Transition metals [13] have been widely used as (passive [14] and active [15] ) templates -alongside other templating interactions such as π-π donor-acceptor interactions [16] and hydrogen bonding [17] in the construction of MIMs. In comparison, the use of lanthanide cations as templates for MIM synthesis is a much more recent development.…”