Optimization and Insights into the Mechanism of Formation of Mechanically Interlocked Derivatives of Single-Walled Carbon Nanotubes.

The mechanical bond provides a stable yet dynamic link between the submolecular components of mechanically interlocked molecules, such as rotaxanes and catenanes. We introduced the mechanical bond as a new tool for the chemical modification of single-walled carbon nanotubes (SWNTs), producing the first mechanically interlocked derivatives of nanotubes (MINTs). To do so, we used U-shaped molecules featuring two units of a SWNT-recognition unit, which were cyclized around the SWNT by means of ring-closing metathesis (RCM). Here we report optimized conditions for the synthesis of MINTs obtained by systematic investigation of the effect of the concentration of the U-shaped molecule 1, reaction time, and catalyst concentration. Analysis of the data also provides insights into the mechanism of formation of MINTs. In particular, the effect of the concentration of 1 supports the formation of a 1⋅SWNT complex. The kinetic data follow a pseudo-first-order behavior that validates the RCM as the rate-determining step. An excess of RCM catalyst leads to the formation of supramolecularly adsorbed linear oligomers of 1.