Artificial Supramolecular Pumps Powered by Light

Abstract

The development of artificial nanoscale motors that can use energy from a source to perform tasks requires systems capable of performing directionally controlled molecular movements and operating away from chemical equilibrium. Here, the design, synthesis and properties of pseudorotaxanes are described, in which a photon input triggers the unidirectional motion of a macrocyclic ring with respect to a non-symmetric molecular axle. The photoinduced energy ratcheting at the basis of the pumping mechanism is validated by measuring the relevant thermodynamic and kinetic parameters. Owing to the photochemical behavior of the azobenzene moiety embedded in the axle, the pump can repeat its operation cycle autonomously under continuous illumination. NMR spectroscopy was used to observe the dissipative non-equilibrium state generated in situ by light irradiation. We also show that fine changes in the axle structure lead to an improvement in the performance of the motor. Such results highlight the modularity and versatility of this minimalist pump design, which provides facile access to dynamic systems that operate under photoinduced nonequilibrium regimes.

Information Thermodynamics for Deterministic Chemical Reaction Networks

“…is is o en recognized as an energy ratchet mechanism in the literature of light-driven molecular motors, and provides the kinetic asymmetry allowing the the motor's functioning [10,24,27,70,71]. From a thermodynamic standpoint, this corresponds to a positive energy ow E for any value of the external force since i)…”

“…(61). is is o en recognized as an information ratchet mechanism providing an additional kinetic bias to the energy ratchet mechanism [10,24,27,70,71]. In the second regime (𝜆 = 436nm, Fig.…”

Sample size dependence of tagged molecule dynamics in steady-state networks with bimolecular reactions: Cycle times of a light-driven pump

“…The choice of a relevant case study is thus oriented towards reaction networks in which the kinetics of the tagged molecule involves bimolecular processes such as self-assembly. Apart from being widespread in natural biochemical networks, self-assembly is a key feature in the broad fields of systems chemistry and artificial supramolecular machines, in which specific tasks are realized thanks to a proper design of the molecular players and a suitable choice of the operative conditions [17][18][19][20][21][22][23] .…”

Second-Generation Light-Fueled Supramolecular Pump

“…Presumably, the Z -azobenzene moiety not only is unable to interact with the macrocycle but also disturbs its π stacking with the pseudostopper unit. Because of this phenomenon, the K E / K Z ratio, whose deviation from unity is key to generate a photoinduced dissipative nonequilibrium state, ,, increases from 3.7 for 2 + to 17 for 3 + .…”

“…Another significant aspect of this system, shared with its precursor, is its ability to use light energy to operate in a dissipative regime away from equilibrium. − Unlike kinetically trapped or metastable nonequilibrium states, a dissipative state can exist only if energy is continuously supplied. − The closed reaction network shown in Figure b consists of chemical reactions, which are subject to microscopic reversibility, and photochemical reactions, which are not. The constants K u ( h ν) and K c ( h ν) of the photochemical branches can be taken as the ratios of the concentrations of the respective products and reactants at the PSS.…”