Synthesis of Molecular Motors Incorporating para ‐Phenylene‐Conjugated or Bicyclo[2.2.2]octane‐Insulated Electroactive Groups

The insulating role of the bicyclo[2.2.2]octane fragment has been theoretically evaluated by comparing the electronic coupling parameter ( V ab ) in 1,4‐bis(ferrocenyl)benzene ( 1 ) and 1,4‐bis(ferrocenyl)bicyclo[2.2.2]octane ( 2 ). The geometries were optimized by DFT and an extended Hückel calculation was performed to evaluate V ab by the dimer splitting method. The calculations showed a 12‐fold decrease of the electronic coupling from 60 meV for 1 to 5 meV for 2 . The second part describes the synthesis of two potential molecular motors with one incorporating the insulating bicyclo[2.2.2]octane fragment. These molecules are based on a ruthenium complex bearing a tripodal stator functionalized to be anchored onto surfaces. The ferrocenyl electroactive groups and the cyclopentadienyl (Cp) rotor are connected through a p ‐phenylene spacer ( 5 ) or through a spacer incorporating an insulating bicyclo[2.2.2]octane moiety ( 6 ).