A translationally active ligand based on a [2]rotaxane molecular shuttle with a 2,2'-bipyridyl core.

A rigid H-shaped, [2]rotaxane molecular shuttle comprised of an axle containing two benzimidazole recognition sites and a central 2,2'-bipyridyl (bipy) group interlocked with a 24-crown-8 (24C8) wheel was synthesized using a threading followed by stoppering protocol. The central bipy chelating unit was shown to act as a speed bump that raised the barrier to shuttling for the [2]rotaxane. Coordination of a PtCl moiety to the bipy unit in a square planar geometry created an insurmountable steric barrier to shuttling.

Orthogonal, modular anion-cation and cation-anion self-assembly using pre-programmed anion binding sites.

Subcomponent self-assembly relies on cation coordination whereas the roles of anions often only emerge during the assembly process. When sites for anions are instead pre-programmed, they have the potential to be used as orthogonal elements to build up structure in a predictable and modular way. We explore this idea by combining cation (M) and anion (X) binding sites together and show the orthogonal and modular build up of structure in a multi-ion assembly.

Dynamics of a [2]rotaxane wheel in a crystalline molecular solid.

An H-shaped [2]rotaxane comprising a bis(benzimidazole) axle and a 24-membered crown ether wheel appended with four trityl groups forms a highly crystalline material with enough free volume to allow large amplitude motion of the interlocked macrocycle. Variable-temperature (VT) H solid-state nuclear magnetic resonance (SSNMR) was used to characterize the dynamics of the [2]rotaxane wheel in this material.

Zero-Overlap Fluorophores for Fluorescent Studies at Any Concentration.

Fluorophores are powerful tools for the study of chemistry, biology, and physics. However, fluorescence is severely impaired when concentrations climb above 5 μM as a result of effects like self-absorption and chromatic shifts in the emitted light. Herein, we report the creation of a charge-transfer (CT) fluorophore and the discovery that its emission color seen at low concentrations is unchanged even at 5 mM, some 3 orders of magnitude beyond typical limits.

Apical Functionalization of Tribenzotriquinacenes.

The introduction of one alkyne moiety at the central carbon atom of the tripodal tribenzotriquinacene scaffold allows easy access to a great variety of apically functionalized derivatives. The spatially well-separated arrangement of different functional units on the convex face and outer rim was further proven by single-crystal X-ray studies. Subsequent modifications that feature a general protecting group-free strategy for the demethylation of protected catechols in the presence of a terminal alkyne group, an azide-alkyne Huisgen cycloaddition, and Sonogashira cross-coupling reactions showcase the high synthetic potential of this modular approach for tribenzotriquinacene derivatization.

Reversible Assembly of a Supramolecular Cage Linked by Boron-Nitrogen Dative Bonds.

Boron-nitrogen dative bonds provide a suitable motif for reversible, yet strong and directed interactions, leading to the highly efficient self-assembly of small organic building blocks into supramolecular cage structures. A bipyramidal [2+3] assembly, as the first example of a supramolecular cage mediated by BN dative bonds that exists as a discrete species in solution, is quantitatively obtained from a tribenzotriquinacene-based trisboronate ester and 1,4-diazabicyclo[2.2.