Boronic ester-templated pre-rotaxanes as versatile intermediates for rotaxane -functionalisation.

We report on the synthesis of [2]rotaxanes from vicinal diols through dynamic covalent boronic ester templates, as well as the use of the boronic ester for rotaxane post-functionalisation. A boronic acid pincer ligand with two alkene-appended arms was condensed with a linear diol-containing thread, and ring-closing metathesis established a pre-rotaxane architecture along with a non-entangled isomer. Advanced NMR spectroscopy and mass spectrometry unambiguously assigned the isomers and revealed that the pre-rotaxane was in equilibrium with its hydrolyzed free [2]rotaxane form.

Switchable protection and exposure of a sensitive squaraine dye within a redox active rotaxane.

In nature, molecular environments in proteins can sterically protect and stabilize reactive species such as organic radicals through non-covalent interactions. Here, we report a near-infrared fluorescent rotaxane in which the stabilization of a chemically labile squaraine fluorophore by the coordination of a tetralactam macrocycle can be controlled chemically and electrochemically. The rotaxane can be switched between two co-conformations in which the wheel either stabilizes or exposes the fluorophore.

para-Phenylenediamine Dimer as a Redox-Active Guest for Supramolecular Systems.

Redox-active components are highly valuable in the construction of molecular devices. We combined two p-phenylenediamines (p-PDA) with a biphenyl (BiPhe) unit to prepare a supramolecular guest 4 consisting of three binding sites for cucurbit[7/8]uril (CBn) and/or cyclodextrins (CD). Supramolecular properties of 4 were investigated using NMR, UV-vis, mass spectrometry and isothermal titration calorimetry.

Encapsulation in Charged Droplets Generates Distorted Host-Guest Complexes.

The ability of various hydrogen-bonded resorcinarene-based capsules to bind α,ω-alkylbisDABCOnium (DnD) guests of different lengths was investigated in solution and in the gas-phase. While no host-guest interactions were detected in solution, encapsulation could be achieved in the charged droplets formed during electrospray ionisation (ESI). This included guests, which are far too long in their most stable conformation to fit inside the cavity of the capsules.

Binding modes of high stoichiometry guest complexes with a CoL cage uncovered by mass spectrometry.

We demonstrate how different modes of guest binding with a CoL cubic cage can be determined using ESI-MS. High stoichiometry guest binding was observed, with the guests preferentially binding externally, but internal guest inclusion was also seen at higher guest loading.