Synthesis of a [2]rotaxane through first- and second-sphere coordination

In an effort to expand the application of a new template from interpenetrated to interlocked molecular species, we report the synthesis of a new [2]rotaxane by means of both first- and second-sphere coordination of a palladium(II) dichloride subunit

Ion-Mobility Mass Spectrometry for the Rapid Determination of the Topology of Interlocked and Knotted Molecules.

A rapid screening method based on traveling-wave ion-mobility spectrometry (TWIMS) combined with tandem mass spectrometry provides insight into the topology of interlocked and knotted molecules, even when they exist in complex mixtures, such as interconverting dynamic combinatorial libraries. A TWIMS characterization of structure-indicative fragments generated by collision-induced dissociation (CID) together with a floppiness parameter defined based on parent- and fragment-ion arrival times provide a straightforward topology identification. To demonstrate its broad applicability, this approach is applied here to six Hopf and two Solomon links, a trefoil knot, and a [3]catenate.Deutsche Forschungsgemeinschaft (CRC 765 “Multivalency”). Alexander von Humboldt Foundation. Swiss National Science Foundation (PZ00P2_161270). Fondation Wiener-Anspach

Switchable synchronisation of pirouetting motions in a redox-active [3]rotaxane

In this study, the crown/ammonium [3]rotaxane R2 is reported which allows a switchable synchronisation of wheel pirouetting motions. The rotaxane is composed of a dumbbell-shaped axle molecule with two mechanically interlocked macrocycles which are decorated with a redox-active tetrathiafulvalene (TTF) unit. Electrochemical, spectroscopic, and electron paramagnetic resonance experiments reveal that rotaxane R2 can be reversibly switched between four stable oxidation states (R2, R2˙+, R22(˙+), and R24+). The oxidations enable non-covalent, cofacial interactions between the TTF units in each state—including a stabilised mixed-valence (TTF2)˙+ and a radical-cation (TTF˙+)2 dimer interaction—which dictate a syn (R2, R2˙+, and R22(˙+)) or anti (R24+) ground state co-conformation of the wheels in the rotaxane. Furthermore, the strength of these wheel–wheel interactions varies with the oxidation state, and thus electrochemical switching allows a controllable synchronisation of the wheels’ pirouetting motions. DFT calculations explore the potential energy surface of the counter-rotation of the two interacting wheels in all oxidation states. The controlled coupling of pirouetting motions in rotaxanes can lead to novel molecular gearing systems which transmit rotational motion by switchable non-covalent interactions

Photosensitive drugs: a review on their photoprotection by liposomes and cyclodextrins.

Nowadays, an exciting challenge in the drug chemistry and technology research is represented by the development of methods aimed to protect molecular integrity and therapeutic activity of drugs from effects of light. The photostability characterization is ruled by ICH (The International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use), which releases details throughout basic protocols of stability tests to be performed on new medicinal products for human use. The definition of suitable photoprotective systems is fundamental for pharmaceutical manufacturing and for human healthy as well, since light exposure may affect either drugs or drug formulations giving rise even to allergenic or mutagenic by-products. Here, we summarize and discuss the recent studies on the formulation of photosensitive drugs into supramolecular systems, capable of entrapping the molecules in a hollow of their structure by weak noncovalent interactions and protecting them from light. The best known supramolecular matrices belong to the 'auto-assembled' structures, of which liposomes are the most representative, and the 'host-guest' systems, of which cyclodextrins represent the most common 'host' counterpart. A relevant number of papers concerning the use of both liposomes and cyclodextrins as photoprotection systems for drugs has been published over the last 20 years, demonstrating that this topic captures interest in an increasing number of researchers