An azobenzene container showing a definite folding - synthesis and structural investigation.

Abdulselam Adam,Saber Mehrparvar,Gebhard Haberhauer

doi:10.3762/bjoc.15.156

Abdulselam Adam, Saber Mehrparvar + Show 1 more

Open Access

https://doi.org/10.3762/bjoc.15.156

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Abstract

The combination of photo-switchable units with macrocycles is a very interesting field in supramolecular chemistry. Here, we present the synthesis of a foldable container consisting of two different types of Lissoclinum macrocyclic peptides which are connected via two azobenzene units. The container is controllable by light: irradiation with UV light causes a switching process to the compact cis,cis-isomer, whereas by the use of visible light the stretched trans,trans-isomer is formed. By means of quantum chemical calculations and CD spectroscopy we could show that the trans→cis isomerization is spatially directed; that means that one of the two different macrocycles performs a definite clockwise rotation to the other, caused by irradiation with UV light. For the cis→trans isomerization counterclockwise rotations are found. Furthermore, quantum chemical calculations reveal that the energy of the cis,cis-isomer is only slightly higher than the energy of the cis,trans-isomer. This effect can be explained by the high dispersion energy in the compact cis,cis-isomer.

Highlights

In supramolecular chemistry rigid scaffolds are required to arrange different recognition units in predefined distances and spatial orientation to each other [1]
The orientation and the distance between the recognition units are determined by the type and size of the macrocyclic platform, e.g., if all of the amino acid side chains are of the same configuration, they are presented on one face of the macrocycle in a convergent manner
That means the chiral information is transferred from both macrocycles to the cis-azobenzene units in cis,trans-(M)-10 and cis,cis-(M,M)-10 and the two different macrocycles perform a definite clockwise rotation to the other caused by irradiation with UV light and a counterclockwise rotation when the compound is exposed to visible light

Summary

Introduction

In supramolecular chemistry rigid scaffolds are required to arrange different recognition units in predefined distances and spatial orientation to each other [1]. Two imidazole-containing macrocycles are linked to each other by two azobenzene units (Figure 2). We present the synthesis and the structural investigation of a switchable chiral container in which two different C2-symmetric artificial Lissoclinum cyclopeptides are connected by two azobenzene bridges.

Results

Conclusion