Mechanics of Molecule-Gears with Six Long Teeth

On a Pb(111) surface in its superconducting state, the construction of a train of two and three hexa- tert -butylbiphenylbenzene molecule-gears (HB-BPB) is presented using a single Cu ad-atom rotation axle per molecule-gear for the two first ones. The new presented HB-BPB gears have been designed and synthesized with very long biphenyl teeth to minimize the number of Cu rotation axles for a long train construction when engaged at larger interaxle distances. It leads to a strong mechanical entanglement between the gears and renders a transmission of rotation along the train difficult. To minimize this classical entanglement, a practical solution is presented by using a native Pb(111) surface monoatomic step and by positioning each molecule-gear of the train at different monoatomic step heights on the supporting surface. This allows the construction of functioning long molecule-gear trains.