Synthetic strategies towards mechanically interlocked oligomers and polymers

Abstract

Synthetic methodologies towards the preparation of oligomeric and polymeric mechanically interlocked molecules are described, including both covalent strategies and self-assembly approaches.

Structural Flexibility in Metal-Organic Cages

“…Mechanically interlocked molecules have been widely investigated for their use as molecular machines due to the high degree of co-conformational freedom between their components afforded by the lack of covalent bonds ( Heard and Goldup, 2020 ). Consequently there has been considerable interest in the development of mechanically interlocked ligands ( Lewis et al, 2017 ) and the use of metal ions/nodes to periodically arrange them ( Hoyas Pérez and Lewis, 2020 ; Wilson and Loeb, 2020 ). Lewis and co-workers recently reported the synthesis of [2]rotaxane ligand 30 ( Figure 4C ), wherein one of the stopper units preventing escape of the macrocycle component was based on dipyridyl ligand 9 ( Wong et al, 2020 ).…”

Chemically modified nucleic acids and DNA intercalators as tools for nanoparticle assembly

“…20), but many others exist such as molecular knots and Borromean rings. 161 A rotaxane configuration consists of a macrocycle (ring) which is threaded onto a dumbbell shaped molecule. The name rotaxane derives from the Latin words rota (wheel) and axis (axle) and the dumbbell structure is referred to as the axle.…”

“…168,169 Whilst these early attempts were low yielding and inefficient, catenanes and rotaxanes can now be synthesised from a plethora of small discrete molecules and oligomers in high yield. 161 This section will focus on the use of DNA catenanes and rotaxanes for the programmable self-assembly of nanoparticles. We will discuss their preparation and the chemical modifications that enable these constructions.…”

“… 168,169 Whilst these early attempts were low yielding and inefficient, catenanes and rotaxanes can now be synthesised from a plethora of small discrete molecules and oligomers in high yield. 161 …”

Aqueous assembly of a (pseudo)rotaxane with a donor–π–acceptor axis formed by a Knoevenagel condensation

“…A variety of coupling reactions have been employed, with the copper(I)-catalysed azide-alkyne 1,3cycloaddtion (CuAAC) as "click" reaction being particularly popular, 10,16 combining mild conditions and the concomitant tolerance for a large variety of functional groups with high yields, especially in (metal-)templated assembly strategies. [25][26][27][28] However, in contrast to the irreversible CuAAC, only stoppering by reversible transformations might provide thermodynamic control over the formed superstructures. So far mainly imine condensations 29,30 and olefin metatheses 31 have been used for this purpose.…”