Themed collection In celebration of Paul Beer’s 60th Birthday

This Perspective examines the versatility of the dithiocarbamate ligand in metal-directed self-assembly. The ligand has been utilised to form a variety of well-defined architectures, which can participate in host–guest chemistry and in stabilising gold nanoparticles.

The development of solution-based anion receptor molecules which exploit halogen bonding interactions is an emerging area of research. This Feature Article reviews recent advances which have been made in this rapidly developing field, surveying the use of iodoperfluoroarene, haloimidazolium and halotriazole/triazolium halogen-bond-donor motifs in anion receptor design and describing the application of mechanically interlocked rotaxane and catenane frameworks as halogen bonding anion host systems.

This feature article summarises the developments made in the surface assembly and characterisation of mechanically interlocked molecules, including recent progress in exploiting templating methods to interlock molecular systems on surfaces.

The rational development of a general anion templation strategy for the construction of interpenetrated and interlocked molecular structures based upon the coupling of anion recognition with ion-pairing is described.

Surface pre-organisation within robust amidoferrocene self-assembled monolayers can be exploited in the selective electrochemical sensing of anions in both organic and aqueous media.

Interlocked host molecules are demonstrated to exhibit high degrees of molecular recognition which, when coupled to appended reporter groups, make them highly promising candidates for the development of molecular sensors.

We discuss the various roles that metal ions play, and their advantages, in the synthesis of mechanically interlocked materials.

Key developments including the utilization of new metal cation and anion templates, dynamic combinatorial chemistry, molecular machines and the incorporation of catenanes onto surfaces and into metal organic frameworks are reviewed.

The potential of the sulfate dianion to template the formation of complex molecular architectures including helixes, capsules, and interlocked systems is discussed.

A new strategic anion templation methodology has been developed for the synthesis of interpenetrated pseudorotaxane, rotaxane and catenane structures, designed with a view to producing new highly selective anion receptors after template removal.

Alpha-cyclodextrin based anion receptors containing halogen and hydrogen bond donor motifs display selective association of perrhenate in neutral aqueous media.

A tetradentate halogen bond donor foldamer receptor framework is shown to exhibit enhanced anion recognition and chiral discrimination properties.

Novel halogen bonding chiral (S)-1,1′-bi-2-naphthol-based receptor molecules significantly enhance enantioselective anion recognition and electrochemical sensing compared to their hydrogen bonding analogues.

The first redox-active halogen bonding anion receptors display larger electrochemical voltammetric responses to halide binding compared to their hydrogen bonding analogues.

The synthesis of a water soluble [2]rotaxane is reported using hydrophilic secondary rim functionalised permethylated β-cyclodextrin derivatives as the axle stopper groups. The rotaxane recognises halide anions in pure water with impressive selectivity over sulfate.

The first example of perrhenate anion binding and fluorescence sensing in water by a halogen bond donor is reported.

The first example of a catenane synthesised using a nitrate anion template is demonstrated. The resulting interlocked host is capable of selectively recognising nitrate over a range of more basic oxoanions in a competitive organic–aqueous solvent mixture.

Four neutral [2]rotaxane host systems, synthesised via anion templation, are shown to recognise halide anions in aqueous solvent mixtures.

The first nitrate templated synthesis of an interlocked structure is reported. The resulting rotaxane host selectively recognises nitrate in preference to other mono-oxoanions in aqueous solvent mixtures.

The 2-iodoimidazolium group is exploited in the anion-templated assembly of pseudorotaxanes with isophthalamide containing macrocycles.

The dansyl fluorophore ligated to gold nanoparticles via imidazole and amine groups affords conjugates capable of detecting micromolar concentrations of the chemical warfare agent sulfur mustard by a fluorescence switching ‘ON’ displacement assay.

A redox-active [3]rotaxane exhibits different binding and electrochemical responses to chloride and sulfate anions in competitive solvent media.

The first example of a catenane capable of performing circumrotation via an anion switching methodology is described; of particular interest is a conformational locking mechanism which results from chloride coordination in the catenane binding cavity.

A new calix[4]diquinone species has been found to bind simple ion-pair systems strongly where no discernible affinity for either of the free ions is observed.

A new photo-active rhenium(I) bipyridyl based rotaxane has been synthesised making use of a strategy founded on anion templation. By virtue of the unique interlocked structural cavity, the rotaxane selectively senses hydrogensulfate using luminescence spectroscopy.

Simple preorganised indolo[2,3-a]carbazole derivatives are shown to recognise and sense anionic guest species using fluorescence spectroscopy.

A series of new photo-active rhenium(I) bipyridyl based pseudorotaxane complexes is assembled via halide anion templation.

The synthesis of calix[4]arene based dendrimers containing up to seven calix[4]arene moieties is described, including the X-ray crystal structure of a tris-calix[4]arene branching derivative.

Two bistable halogen and hydrogen bonding-naphthalene diimide [2]rotaxanes have been prepared and the system incorporating a halogen bond donor anion recognition site is demonstrated to exhibit superior anion induced translational motion of the macrocyclic wheel component relative to the hydrogen bonding analogue.

The first ferrocene containing catenanes, in solution and on a surface, have been prepared by chloride anion templation.

The synthesis and cation recognition studies of two novel heteroditopic [2]catenanes that are capable of exhibiting cation induced reversible rotary motion is described. Barium cation complexation triggers a partial intra-ring rotation of the catenanes which is reversed upon addition of sulfate.

A new versatile tetrakis-imidazolium macrocycle for use in supramolecular applications is reported. It displays excellent affinities for π-electron rich neutral guests such as 1,5-dihydroxynaphthalene derivatives and TTF, providing opportunities for the construction of interlocked molecules, as well as exhibiting extensive and potent anion coordination chemistry.

Neutral heteroditopic [2]rotaxane ion-pair host systems were synthesised via a copper(II)-directed metal template strategy and shown to undergo cooperative anion recognition with a co-bound zinc(II) cation.

The preparation and anion binding properties of 1,3,5-tri-substituted benzene platform-based tripodal receptors containing halogen bonding (XB) iodo-imidazolium and iodo-triazolium motifs, and hydrogen bonding (HB) analogues are described.

Incorporating halogen bonding into an interlocked [2]rotaxane anion host system results in unprecedented nitrate recognition in 90% water.

A dicationic halogen bonding rotaxane displays enhanced binding and selectivity for bromide over other halides and nitrate and dihydrogen phosphate oxoanions in contrast to an all hydrogen bonding counterpart which is attributed to chelated charge assisted halogen bonding interactions.

Fluoride binding by lanthanide complexes of a range of DOTA tetraamides changes the magnetic anisotropy at the metal centre from an easy axis to an easy plane.

Dramatic changes are observed in both the NMR and luminescence spectra of LnDTMA complexes on addition of fluoride, consistent with a change in the nature of the magnetic anisotropy at the paramagnetic lanthanide centre.

A [2]rotaxane anion host that switches selectivity from dihydrogen phosphate to the halides upon substituting a hydrogen bond donor group for a halogen bond donor group within the axle component is described.

Halogen-bonding iodotriazole anion recognition groups have been integrated into a picket-fence zinc(II)-metalloporphyrin scaffold to produce a receptor with enhanced halide anion recognition and sensing applications.

A novel bis-triazole pyridinium axle containing rotaxane, prepared by a chloride anion templated ring closing metathesis clipping strategy, exhibits selectivity for halide anions over oxoanions with a notable preference for bromide being shown amongst the halides.

We report the synthesis and structural characterisation of a series of gold- and palladium-containing imidazolium salts. The reduction of these salts can give nanoparticles stabilised either by surfactant or carbene species which demonstrate catalytic activity even while ligands are attached to the metal surface.

The effect of varying the size of the macrocycle component on the formation of anion templated imidazolium interpenetrated assemblies and on the recognition properties of analogous interlocked rotaxane host systems is investigated.

A meta-xylenediamide containing rotaxane is prepared by a novel synthetic procedure, and exhibits selective halide anion recognition.

Anion sensing by ferrocene functionalized receptors is significantly enhanced when adsorbed at gold surfaces.

The fine tuning of selectivity and strength of cooperative ion-pair recognition using heteroditopic calix[4]arene-based receptors has been achieved. These modulations in binding properties are found to depend critically on the cation binding site and the macrocyclic nature of the receptors.

Novel halo-derivatised calix[4]tubes exhibit exceptional selectivity for potassium as evidenced by NMR, ESMS and molecular modelling studies.