Scientists in Germany have moved a step closer to making molecular wheels after reporting a one-step self-assembly pathway to a molecular axle and spoke set. 

Technomimetic molecules are molecules designed to mimic the shape and motion of macroscopic objects. The axle unit, sturdy spokes and circular rim of real-life wheels have not yet been successfully copied on the molecular scale.

Professor Michael Schmittel and Dr Prasenjit Mal at the University of Siegen, Germany, made a supramolecular spoke set based on a hexakis-terpyridine scaffold. They formed a copper complex of the scaffold and capped the spokes with phenanthroline ligands. The phenanthroline ligands act as the rim elements which, when linked together by a covalent or coordinative bond, will form the rim of the completed wheel. Investigations into the best way to link the rim elements are currently underway in Schmittel's lab. 

Schmittel thinks the development of new technomimetic molecules still represents a huge challenge to chemists. 'While it is uncertain whether individual technomimetic molecules will ever be of any practical use, the intellectual challenge required for their realisation should become a major driving force for new developments,' he said.

Joanne Thomson