π-Stacking Stopper-Macrocycle Stabilized Dynamically Interlocked [2]Rotaxanes.

Sing-Ming Chan,Chak-Shing Kwan,Fung-Kit Tang,Ching-Yau Lam,Ken Cham-Fai Leung,Sam C K Hau

doi:10.3390/molecules26154704

Sing-Ming Chan, Chak-Shing Kwan + Show 4 more

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https://doi.org/10.3390/molecules26154704

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Abstract

The synthesis of mechanically interlocked molecules is valuable due to their unique topologies. With π-stacking intercomponent interaction, e.g., phenanthroline and anthracene, novel [2]rotaxanes have been synthesized by dynamic imine clipping reaction. Their X-ray crystal structures indicate the π-stackings between the anthracene moiety (stopper) on the thread and the (hetero)aromatic rings at the macrocycle of the rotaxanes. Moreover, the length of glycol chains affects the extra π-stacking intercomponent interactions between the phenyl groups and the dimethoxy phenyl groups on the thread. Dynamic combinatorial library has shown at best 84% distribution of anthracene-threaded phenanthroline-based rotaxane, coinciding with the crystallography in that the additional π-stacking intercomponent interactions could increase the thermodynamic stability and selectivity of the rotaxanes.

Highlights

The synthesis of mechanically interlocked molecules, such as [n]rotaxanes and [n]catenanes [1,2,3,4], has drawn interest due to their unique topologies
For the [n]rotaxanes, templated-direct syntheses using secondary dialkylammonium (R2NH2+) ions are involved in threading followed by stoppering [15], slippage [16,17,18,19] and clipping approaches [20,21] Various macrocycles, such as dibenzo[24]crown-8 (DB24C8) and benzo[21]crown-7 (B21C7), can be threaded through by the dialkylammonium (R2NH2+) ions with sufficiently high binding constant [22,23,24]
In 2001, Stoddart and co-workers developed the dynamic clipping on R2NH2+ ions for [2]rotaxane synthesis [25]

Summary

Introduction

The synthesis of mechanically interlocked molecules, such as [n]rotaxanes and [n]catenanes [1,2,3,4], has drawn interest due to their unique topologies. They have been applied in the designs of molecular machinery [5,6,7,8] and molecular sensing [9,10,11,12,13,14]. As being part of the dynamic covalent chemistry (DCC) [21,26,27], the dynamic clipping approach allows self-error checking and self-sorting to favor the most thermodynamically stable rotaxane as the major product based on equilibrium reactions. Besides [2]rotaxanes, efficient methods for constructing dendritic [n]rotaxanes [28,29,30,31,32] homocircuit [n]rotaxanes [33,34,35,36,37,38] and heterocircuit [n]rotaxanes [39,40,41,42,43,44,45] have recently been investigated

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