Luminescent chiral lanthanide(III) complexes as potential molecular probes

Coordination chemistry of amide-functionalised tetraazamacrocycles: structural, relaxometric and cytotoxicity studies

Three different tetraazamacrocyclic ligands containing four amide substituents that feature groups (namely allyl, styryl and propargyl groups) suitable for polymerisation have been synthesised. Gadolinium(III) complexes of these three ligands have been prepared as potential monomers for the synthesis of polymeric MRI contrast agents. To assess the potential of these monomers as MRI contrast agents, their relaxation enhancement properties and cytotoxicity have been determined. A europium(III) complex of one of these ligands (with propargyl substituents) is also presented together with its PARACEST properties. In addition, to gain further insight into the coordination chemistry of the tetra-propargyl substituted ligand, the corresponding zinc(II) and cadmium(II) complexes have been prepared. The X-ray crystal structures of the tetra-propargyl ligand and its corresponding gadolinium(III), zinc(II) and cadmium(II) complexes are also presented.

Strong Circularly Polarized Luminescence from Highly Emissive Terbium Complexes in Aqueous Solution

Two luminescent terbium(III) complexes have been prepared from chiral ligands containing 2-hydroxyisophthalamide (IAM) antenna chromophores and their non-polarized and circularly-polarized luminescence properties have been studied. These tetradentate ligands, which form 2:1 ligand/Tb(III) complexes, utilize diaminocyclohexane (cyLI) and diphenylethylenediamine (dpenLI) backbones, which we reasoned would impart conformational rigidity and result in Tb(III) complexes that display both large luminescence quantum yield (Φ) values and strong circularly polarized luminescence (CPL) activities. Both Tb(III) complexes are highly emissive, with Φ values of 0.32 (dpenLI-Tb) and 0.60 (cyLI-Tb). Luminescence lifetime measurements in H(2)O and D(2)O indicate that while cyLI-Tb exists as a single species in solution, dpenLI-Tb exists as two species: a monohydrate complex with one H(2)O molecule directly bound to the Tb(III) ion and a complex with no water molecules in the inner coordination sphere. Both cyLI-Tb and dpenLI-Tb display increased CPL activity compared to previously reported Tb(III) complexes made with chiral IAM ligands. The CPL measurements also provide additional confirmation of the presence of a single emissive species in solution in the case of cyLI-Tb, and multiple emissive species in the case of dpenLI-Tb.

Usual Molecules in Unusual Environments Displaying Unusual Properties

The design of porous solids of controlled molecular geometry for various applications is a challenge of enormous technological and scientific importance. The placing of organic molecules between the layers of certain inorganic salts leads to enduring, solid materials where the confinement induces the organic molecules to change their properties or even display new ones at the supramolecular level. Many years ago, Feynman asked the question ‘What would the properties of materials be if we could really arrange the atoms (molecules) the way we want them?’. Chemistry, Physics, Engineering and even Biology are nowadays highly intertwined in the pursuing of Feynman’s ambition. However, despite all the huge efforts and smart developments, the finding of new materials is as yet, for the time being, quite open a field that allows for many serendipity-driven discoveries. In this context, we have a relatively large experience in the building of supramolecular scaffolds based in laminar zirconium phosphate (ZrP) containing covalently bonded phosphonates. In this paper, a short review will be presented concerning our past achievements and recent progress in the synthesis of organic-inorganic materials based in layered ZrP.