title: Autonomous artificial nanomotor powered by sunlight.
abstract: Light excitation powers the reversible shuttling movement of the ring component of a rotaxane between two stations located at a 1.3-nm distance on its dumbbell-shaped component. The photoinduced shuttling movement, which occurs in solution, is based on a "four-stroke" synchronized sequence of electronic and nuclear processes. At room temperature the deactivation time of the high-energy charge-transfer state obtained by light excitation is approximately 10 micros, and the time period required for the ring-displacement process is on the order of 100 micros. The rotaxane behaves as an autonomous linear motor and operates with a quantum efficiency up to approximately 12%. The investigated system is a unique example of an artificial linear nanomotor because it gathers together the following features: (i) it is powered by visible light (e.g., sunlight); (ii) it exhibits autonomous behavior, like motor proteins; (iii) it does not generate waste products; (iv) its operation can rely only on intramolecular processes, allowing in principle operation at the single-molecule level; (v) it can be driven at a frequency of 1 kHz; (vi) it works in mild environmental conditions (i.e., fluid solution at ambient temperature); and (vii) it is stable for at least 10(3) cycles.
authors.affiliation: Dipartimento di Chimica G. Ciamician, Università di Bologna, via Selmi 2, 40126 Bologna, Italy. vincenzo.balzani@unibo.it
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Balzani
authors.forename: Miguel
authors.initials: M
authors.lastname: Clemente-León
authors.forename: Alberto
authors.initials: A
authors.lastname: Credi
authors.forename: Belén
authors.initials: B
authors.lastname: Ferrer
authors.forename: Margherita
authors.initials: M
authors.lastname: Venturi
authors.forename: Amar H
authors.initials: AH
authors.lastname: Flood
authors.forename: J Fraser
authors.initials: JF
authors.lastname: Stoddart
mesh_terms: D000042:Absorption; D004563:Electrochemistry; D004581:Electronics; D004583:Electrons; D007700:Kinetics; D008027:Light; D049449:Luminescence; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D020409:Molecular Motor Proteins; D009068:Movement; D036103:Nanotechnology / Q000379:methods*; D010640:Phenothiazines / Q000737:chemistry; D010777:Photochemistry; D010782:Photolysis; D043862:Rotaxanes / Q000737:chemistry; D013053:Spectrophotometry; D013472:Sunlight; D013696:Temperature; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D020409:Molecular Motor Proteins; D010640:Phenothiazines; D043862:Rotaxanes; C031637:phenothiazine