An international team of scientists has developed a predictive thermodynamic approach to designing and tuning mechanically interlocked molecular (MIM) switches. The approach could lead to improved molecular electronic devices, they claim. 

Fraser Stoddart, at Northwestern University, Evanston, US, and colleagues investigated how structural changes to the switches affect their behaviour. They synthesised a library of MIM switch precursors, pseudorotaxanes, based on cyclobis(paraquat-p-phenylene) unit (CBPQT⁴⁺), and investigated how substituents on the CBPQT⁴⁺ units affect the thermodynamics of pseudorotaxane formation with a variety of guests. 

They revealed that the thermodynamic free energy differences observed for the pseudorotaxane formation could be extrapolated to predict the thermodynamics in analogous MIM switches. The investigation could lead to more complex mechanically interlocked molecules with advanced properties and applications, says Stoddart. 

Joanne Thomson