Multiply threaded rotaxanes

Paul R Mcgonigal

doi:10.1080/10610278.2018.1433832

Abstract

Mechanically interlocked molecules (MIMs) of all shapes and sizes are available to Chemists, driving forward progress across a broad range of research areas. Yet, some classes of MIMs remain relatively elusive. This Review summarises the properties of multiply threaded rotaxanes and the methods that have been developed to prepare them, outlining some of the pitfalls and solutions that have been uncovered along the way.

Highlights

Elegant synthetic methods have become available to assemble mechanically interlocked molecules (MIMs) over the past few decades, allowing researchers to investigate and exploit the unique properties of mechanical bonds (1)
The preparation of multiply threaded rings presents challenges: (i) the ring component may have to participate in mutually stabilising reactions with two or more components simultaneously (6); (ii) any noncovalent bonding interactions between components must compete with destabilisation brought about by steric overcrowding in the multicomponent system; (iii) the ring must be sufficiently large to accommodate multiple dumbbells while being small enough to remain mechanically interlocked; and, (iv) large stoppers may be required to prevent slippage (7) of the large ring. It is not entirely straightforward, to extend the design elements of a [2]rotaxane to a multiply threaded [n]rotaxane. This Review aims to provide a survey of the successful syntheses of multiply threaded rotaxanes and a discussion
A modest toolbox of protocols has emerged for the construction doubly threaded rotaxanes

Summary

Introduction

Elegant synthetic methods have become available to assemble mechanically interlocked molecules (MIMs) over the past few decades, allowing researchers to investigate and exploit the unique properties of mechanical bonds (1). Rotaxanes are made up (Figure 1) of ring and dumbbell components. The components remain entangled in this way because of ‘stoppers’ (2) – sterically bulky groups that are too large to pass through the aperture of the ring component – that are present at the ends of each dumbbell. In their most simple form, rotaxanes are formed from just one ring component and one dumbbell component, i.e. a [2]rotaxane. The numerical prefix [n] indicates the total number of independent components present in the MIM. Higher order [n]rotaxanes are created either by (i) encircling a long dumbbell with multiple rings, (ii)

Objectives

Findings

Conclusion