Shape‐Adaptability and Redox‐Switching Properties of a Di‐Gold Metallotweezer

Susana Ibáñez,Eduardo Peris

doi:10.1002/chem.202100794

Abstract

The use of a carbazolyl‐connected di‐gold(I) metallotweezer for the encapsulation of several electron‐poor organic substrates, and a planar Au(III) complex containing a CNC pincer ligand, is described. The binding affinity of the receptor depends on the electron‐deficient character of the planar guest, with larger association constants found for the more electron‐poor guests. The X‐ray diffraction molecular structures of two host:guest adducts show that the host approaches its arms in order to facilitate the optimum interaction with the surface of the planar guests, in a clear example of an guest‐induced fit conformational arrangement. The electrochemical studies of the encapsulation of N,N’‐dimethyl‐naphthalenetetracarboxy diimide (NTCDI) show that the redox active guest is released from the receptor upon one electron reduction, thus constituting an example of redox‐switchable binding.

Highlights

In the 1990s several research groups around the world reasoned that U-shaped molecules with aromatic side walls would form rigid and highly preorganized concave cavities suitable for hosting aromatic guest molecules through π-π stacking interactions.[1]
We thought that the electron-rich environment provided by the pyrene moieties in complex 3 could be used for encapsulating planar electron-deficient organic molecules such as N,N’dimethyl-naphthalenetetracarboxy diimide (NTCDI, 4), 2,4,7trinitro-9-fluorenone (TNFLU, 5) and 2,7-dinitro-4-methoxy-fluorenone (6)
In the case of the titrations with 5 and 6, it was observed that the resonance of the proton bound to the nitrogen of the carbazolyl linker was shifted downfield by 0.9 and 0.2 ppm, respectively, suggesting that for these two guest molecules the formation of the hostguest complex may be stabilized by the presence of hydrogen bonding interactions, most likely with the oxygen atoms from the nitro groups of the guests

Summary

Introduction

In the 1990s several research groups around the world reasoned that U-shaped molecules with aromatic side walls would form rigid and highly preorganized concave cavities suitable for hosting aromatic guest molecules through π-π stacking interactions.[1].

Results

Conclusion