How Secondary and Tertiary Amide Moieties are Molecular Stations for Dibenzo-24-crown-8 in [2]Rotaxane Molecular Shuttles?

Benjamin Riss-Yaw,Frédéric Coutrot,Caroline Clavel,Justine Morin

doi:10.3390/molecules22112017

Abstract

Interlocked molecular machines like [2]rotaxanes are intriguing aesthetic molecules. The control of the localization of the macrocycle, which surrounds a molecular axle, along the thread leads to translational isomers of very different properties. Although many moieties have been used as sites of interactions for crown ethers, the very straightforwardly obtained amide motif has more rarely been envisaged as molecular station. In this article, we report the use of secondary and tertiary amide moieties as efficient secondary molecular station in pH-sensitive molecular shuttles. Depending on the N-substitution of the amide station, and on deprotonation or deprotonation-carbamoylation, the actuation of the molecular machinery differs accordingly to very distinct interactions between the axle and the DB24C8.

Highlights

Since the first interlocked molecular shuttles were reported in the literature in 1994 [1,2], several new systems of recognition have been used to control the localization of a macrocycle around either another macrocycle or a thread in more or less sophisticated interlocked molecules
The deprotonation appeared quite difficult with standard this bases standard bases such as tertiary amines, sodium hydroxide or DBU, as we already encountered such as tertiary amines, sodium hydroxide or DBU, as we already encountered this problem anteriorly problem anteriorly with encircled ammonium moieties in interlocked [2]rotaxane species when no with encircledstrong ammonium moieties in interlocked
Changing from the secondary to the tertiary class of the amide induced a singular behavior of the macrocycle along the thread, and the localization of the dibenzo-24-crown-8 macrocycle (DB24C8) and its interactions with the encircled axle were quite different after deprotonation or deprotonation-carbamoylation of the ammonium template

Summary

Introduction

Since the first interlocked molecular shuttles were reported in the literature in 1994 [1,2], several new systems of recognition have been used to control the localization of a macrocycle around either another macrocycle or a thread in more or less sophisticated interlocked molecules. With the dibenzo-24-crown-8 macrocycle (DB24C8), the use of ammonium [3], as template to direct the interlocking process, is probably the most encountered This template presents the advantage of being possibly concealed through deprotonation, so that the interactions between the template and the macrocycle become annihilated. This possibility is of interest for the construction of multi-stable molecular shuttles, especially if another thread’s moiety of initial weaker affinity is present in the thread.

Synthetic Access to Molecular Shuttles

Characterizations of the Molecular Shuttles

H NMR spectra have been carried carried out at a

Conclusions