Chemically and electrochemically induced expansion and contraction of a ferrocene rotor

A 2,2'-bipyridine-appended ferrocene rotor, 1,1'-di(5-yl-ethynyl-2,2'-bipyridine)ferrocene, can be switched from a folded/stacked (syn) conformation to an extended/unstacked (anti) conformation by the addition of [Cu(CH3CN)(4)](PF6) and 6,6'-dimesityl-2,2'-bipyridine. This extension and contraction process was completely reversible and could be triggered either chemically or electrochemically.