Anion- and Solvent-Induced Rotary Dynamics and Sensing in a Perylene Diimide [3]Catenane.

Timothy A. Barendt,Igor Marques,Vítor Félix,Paul D. Beer,Liliana Ferreira

doi:10.1021/jacs.7b04295

Abstract

A novel dynamic [3]catenane consisting of a large four-station central macrocycle which incorporates a bay tetrachloro-functionalized perylene diimide (PDI) unit and two triazolium anion-binding motifs, mechanically bonded with two smaller isophthalamide-containing macrocycles, is constructed using an anion template synthetic methodology. Proton NMR, electronic absorption, and fluorescence emission spectroscopies together with molecular dynamics simulations are used to investigate the anion recognition- and solvent-dependent dynamic properties of the higher-order mechanically interlocked molecule. Importantly, unprecedented solvent-dependent and anion-binding-induced circumrotatory motion in a hetero[3]catenane system is demonstrated where the exotic dual rotary switching behavior provides a unique and sophisticated mechanism for optical anion sensing in competitive protic organic and aqueous-organic media.

Highlights

Examples of anion controlled rotations of interlocked rings in catenanes are considerably rarer.47−49 To date, discrete anion recognition has served as a stimulus for rotary motion in a homocatenane50 whereas, to the best of our knowledge, the challenging circumrotation of one macrocycle around another in a heterocatenane51 stimulated by anion binding has yet to be realized
A [1+1] macrocyclization reaction was performed in which a tetrachloro-perylene diimide (PDI) bis-biphenyl azide derivative was ring closed with a phenyl trityl bis-alkyne via a double copper(I)-catalyzed azide alkyne cycloaddition (CuAAC) “click” reaction under high dilution conditions to afford the large, rigid central ring (Scheme 1)
A rare example of a dynamic hetero[3]catenane comprised of a large central four-station tetrachloro perylene diimide−bistriazolium ring and two smaller peripheral isophthalamidecontaining macrocycles was synthesized by anion templation and isolated as coordinating chloride and non-coordinating hexafluorophosphate anion salts

Summary

■ INTRODUCTION

In the 26 years since the first rotaxane-based molecular shuttle was reported, mechanically interlocked molecules (MIMs) have become firmly established within the field of nanoscale molecular machines and switches.− The ability to undergo controlled and reversible molecular motion via changes in the relative positions of their constituent parts, as dictated by the nature of the inherent mechanical bond, has been key to this success.− MIMs containing more than two interlocked components may be used to promote motions of even greater complexity that, for example, mimic the actions of an elevator, compressor, or pincer− from the macroscopic world. It is important to note that the chloride anions are more extensively solvated by methanol molecules rather than by chloroform ones, as further discussed in the SI, section 4.2 These MD simulations demonstrate there is some, albeit relatively restricted, pirouetting motion of the peripheral macrocyclic rings in the triazolium-based coconformers of the [3]catenane in solution, while in the PDIbased analogues there is significant restraint, which serves to explain the complex 1H NMR spectra obtained upon the addition of polar protic solvent. Anion-induced circumrotatory motion in the hetero[3]catenane and the colors associated with each anion

Electronic absorption upon the titration of 60

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES