Temperature-controlled, reversible shifting of molecular gear motion in a solid crystal opens latest possibilities for material design.
Gears are a vital part of on a regular basis machines. The flexibility to shift gears, like in a automobile, allows for control of the degree or direction of motion generated, making machines more versatile. Now, a team led by researchers on the Institute for Chemical Response Design and Discovery (WPI-ICReDD) in Hokkaido University has reported a brand new design strategy for realizing molecular-sized gears in crystals and the primary example of controllable molecular gear shifting in a solid material. They developed a crystalline material that incorporates gear-like molecules which will be reversibly shifted between two varieties of motion. The design principle provides a blueprint for the event of versatile, latest materials.
Researchers utilized a gear-shaped molecule called triaryltriazine, which has a middle triazine ring with three phenylene rings attached to it — which act just like the teeth of a gear. By attaching bulky, stationary molecules to the phenylene rings, researchers induced a “clutch stack” arrangement, where adjoining triaryltriazine molecules are rotated 60° from one another, slightly than stacking in the identical orientation.
“The design of the clutch stack was inspired by the mechanical machinery system of the clutch in a automobile,” said Associate Professor Mingoo Jin.
The attached stationary molecules also created enough space for the three phenylene rings to rotate between two positions in a flapping motion. The clutch stack arrangement of the triaryltriazine molecules enabled adjoining molecules to hook on to one another because the phenylene rings rotated, very similar to interlocking gears. This resulted within the correlated motion of all of the molecules within the stack.
When the temperature was raised above a certain threshold, a special correlated motion was observed, wherein phenylene rings underwent a 180° rotation. This alteration in motion was attributed to a phase transition within the crystal that created more room between adjoining molecules, giving the phenylene rings more room to rotate.
Researchers found this alteration in motion may very well be reversed by cooling the crystal, marking the primary time such controllable molecular motion has been observed in a solid. The effect of the molecular gearshift may very well be fine-tuned by adjusting the dimensions and structure of the stationary molecule attached to the gear molecule. This adjustability opens the door to the event of latest functional materials that leverage crystalline molecular machines.
“The subsequent direction for our research could be using geared molecular motion in crystals to control different physical properties of solid-state materials, resembling light emission or thermal behavior” commented Jin.
