Abstract
Host−guest interactions are of central importance in many biological and chemical processes. However, the investigation of the formation and decomplexation of host−guest systems at the single-molecule level has been a challenging task. Here we show that the single-molecule conductance of organoplatinum(II) metallocycle hosts can be enhanced by an order of magnitude by the incorporation of a C60 guest molecule. Mechanically stretching the metallocycle-C60 junction with a scanning tunneling microscopy break junction technique causes the release of the C60 guest from the metallocycle, and consequently the conductance switches back to the free-host level. Metallocycle hosts with different shapes and cavity sizes show different degrees of flexibility to accommodate the C60 guest in response to mechanical stretching. DFT calculations provide further insights into the electronic structures and charge transport properties of the molecular junctions based on metallocycles and the metallocycle-C60 complexes.
Highlights
Host−guest interactions are of central importance in many biological and chemical processes
The maximum mechanical stretching force of the STM tip for the pyridine contact is ~0.8 nN51, which is strong enough to induce the structural deformation of the metallocycles and the release of the C60 guest. These results suggest that the driving force of forming these metallocycle-C60 host–guest complexes is a weak noncovalent interaction, where the shape and cavity size of the metallocycle host play a vital role in the complexation
The linear Benesi–Hildebrand plot suggests a 1:1 host–guest binding ratio of 6 with C60 and the binding constant was calculated to be 4.1 × 105 M−1. These results suggest that the driving force of forming the target host–guest complexes is derived from the donor–acceptor interactions between the electron-rich metallocylic skeleton and the electron-deficient of C6054
Summary
Host−guest interactions are of central importance in many biological and chemical processes. We measure the conductance and study the charge transport in three supramolecular metallocycles and their host–guest complexes with C60 with STMBJ.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
