In the quest for new molecular wheels, octahedral 18-electron trans-alkynylbis(1,2-bis-(diphenylphosphino ) ethane)ruthenium(II) complexes 7 (Fig. 1) appeared to be good candidates, as the low rotation barrier around the alkyne bond might allow a free rotation while the bulky phosphine ligands could act as a tire to interact with metallic surfaces. Good physisorption on metallic surfaces, which has been demonstrated to be crucial for a rolling motion of the wheels, 4b, 5a and ...
![1,3,5-tris[2-(4-ethynylphenyl)ethynyl]benzene Structure](https://image.chemsrc.com/caspic/372/211739-82-1.png)