Kinetic and energetic insights into the dissipative non-equilibrium operation of an autonomous light-powered supramolecular pump.

Natural and artificial autonomous molecular machines operate by constantly dissipating energy coming from an external source to maintain a non-equilibrium state. Quantitative thermodynamic characterization of these dissipative states is highly challenging as they exist only as long as energy is provided. Here we report on the detailed physicochemical characterization of the dissipative operation of a supramolecular pump.

Photoinduced Autonomous Nonequilibrium Operation of a Molecular Shuttle by Combined Isomerization and Proton Transfer Through a Catalytic Pathway.

We describe a [2]rotaxane whose recognition sites for the ring are a dibenzylammonium moiety, endowed with acidic and H-bonding donor properties, and an imidazolium center bearing a photoactive phenylazo substituent. Light irradiation of this compound triggers a network of / isomerization and proton transfer reactions that enable autonomous and reversible ring shuttling away from equilibrium.

Artificial Supramolecular Pumps Powered by Light.

Invited for the cover of this issue is Alberto Credi and co-workers at the University of Bologna and National Research Council, Bologna, Italy. The image represents the photostationary non-equilibrium operation of supramolecular pumps as a hydraulic circuit in which water flows between reservoirs. Read the full text of the article at 10.

Artificial Supramolecular Pumps Powered by Light.

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.

Threading of Conformationally Stable Calix[6]arene Wheels Substituted at the Methylene Bridges.

Calix[6]arenes disubstituted at the methylene bridges, which are stable in the cone or 1,2,3-alternate conformation, form pseudorotaxanes with dialkylammonium axles. The cone wheel-based pseudorotaxanes are 10-100 times more stable than those obtained with the native conformationally mobile calix[6]arene wheel, as a consequence of their higher degree of preorganization. The threading of conformationally stable 1,2,3-alternate calix[6]arenes is unprecedented in the literature.

Effect of Microwave-Assisted Extraction on Polyphenols Recovery from Tomato Peel Waste.

This study describes the application of microwave-assisted extraction (MAE) as an innovative technique for isolation of polyphenols from tomato peel waste. Effects of solvents, temperatures (25, 55 and 90 °C) and times (5 and 10 min) were evaluated with regard to total phenols (TP), total flavonoids (TF) and phenolic compound contents. Tomato peel extracts contain high amounts of kaemferol-3-O-rutinoside (8.