Coordination-cage binding and catalysed hydrolysis of organophosphorus chemical warfare agent simulants.

The use of organophosphorus chemical warfare agents still remains an ongoing global threat. Here we investigate the binding of small-molecule organic guests including phosphate esters, sulfonate esters, carbonate esters and a sulfite ester - some of which act as simulants for organophosphorus chemical warfare agents - in the cavity of a water-soluble coordination cage. For several of these guest species, binding constants in the range 10 to 10 M were determined in water/DMSO (98 : 2 v/v) solution, through a combination of fluorescence and H NMR spectroscopy, and subsequent fitting of titration data to a 1 : 1 binding isotherm model.

Photoswitching of Co(ii)-based coordination cages containing azobenzene backbones.

Inclusion of photoswitchable azobenzene units as spacers into ditopic bridging ligands L and L, containing two chelating pyrazolyl-pyridine termini, allows formation of metal complex assemblies with Co(ii) that undergo a range of light-induced structural transformations. One notable result is the light-induced conversion of a Co(L) dinuclear triple helicate (based on the ligand isomer) to a -symmetric Co(L) assembly, assumed to be an edge-bridged tetrahedral cage, based on the ligand isomer. Another is the preparation of a series of Co(L) complexes, of which Co(-L) was crystallographically characterised and consists of a pair of Co(L) double helicates connected by an additional two bridging ligands which span the pair of helicate units, giving a cyclic Co array in which one and then two bridging ligands alternate around the periphery.

Orthogonal binding and displacement of different guest types using a coordination cage host with cavity-based and surface-based binding sites.

The octanuclear Co(ii) cubic coordination cage system (or if it bears external water-solubilising substituents) has two types of binding site for guests. These are (i) the partially-enclosed central cavity where neutral hydrophobic organic species can bind, and (ii) the six 'portals' in the centres of each of the faces of the cubic cage where anions bind formation of a network of CH⋯X hydrogen bonds between the anion and CH units on the positively-charged cage surface, as demonstrated by a set of crystal structures. The near-orthogonality of these guest binding modes provides the basis for an unusual dual-probe fluorescence displacement assay in which either a cavity-bound fluorophore (4-methyl-7-amino-coumarin, ; = 440 nm), or a surface-bound anionic fluorophore (fluorescein, ; = 515 nm), is displaced and has its emission 'switched on' according to whether the analyte under investigation is cavity-binding, surface binding, or a combination of both.

Qualitative colorimetric analysis of a Ir(iii)/Eu(iii) dyad in the presence of chemical warfare agents and simulants on a paper matrix.

The addition of G- and V-series organophosphorus chemical warfare agents and simulants to a paper-based assay of a dual-luminescent Ir(iii)/Eu(iii) dyad generated different emissive responses between the classes and compound types. The emission responses are complex and based not only on altering the balance between red Eu(iii)-based and blue Ir(iii)-based luminescent components, but also incorporate other factors such as analyte volatility, concentration and UV absorption. The extent of this emission colour change was analysed colorimetrically and related to the change in RGB output over time.