A Lanthanide Luminescent Cation Exchange Material Derived from a Flexible Tricarboxylic Acid 2,6-Bis(1,2,3-triazol-4-yl)pyridine (btp) Tecton

Generating water/MeOH-soluble and luminescent polymers by grafting 2,6-bis(1,2,3-triazol-4-yl)pyridine (btp) ligands onto a poly(ethylene-alt-maleic anhydride) polymer and cross-linking with terbium(III)

The synthesis of two new polymers made from P(E-alt-MA) (poly(ethylene-alt-maleic anhydride) and possessing 2,6-bis(1,2,3-triazol-4-yl)pyridine (btp) ligand side chains in 3 and 6 mol%, respectively (P1 and P2, respectively) is described. These polymers were shown to be soluble in MeOH solution and, in the case of P1, also in water, while P2 needed prolonged heating to enable water dissolution. Btp ligands are known for coordinating both d- and f-metal ions and so, herein, we demonstrate by using both UV-Vis absorption, fluorescence emission, as well as time-gated phosphorescence spectroscopies, that both P1 and P2 can bind to Tb(III) ions to give rise to luminescent polymers. From the analysis of the titration data, which demonstrated large changes in the emission intensity properties of the polymer upon Tb(III) binding (ground state changes were also clearly observed, with the absorption being red-shifted at lower energy), we show that the dominant stoichiometry in solution is 1 : 2 (M : L; Tb(III) : btp ratio) which implies that two btp ligands from the polymer background are able to crosslink through lanthanide coordination and that the backbone of the polymer is very likely to aid in coordinating the ions.

Macrocyclic vs. [2]catenane btp structures: influence of (aryl) substitution on the self templation of btp ligands in macrocyclic synthesis

The synthesis of four 2,6-bis(1,2,3-triazol-4-yl)pyridine (btp) olefin based ligands 3, 4, 11 and 12 is described and their attempted use to form mechanically interlocked molecules using ring closing metatheses (RCM) reactions. The btp ligands were modified in two ways, in 3 and 4 the aryl substitution pattern was changed from 4^th position to 3^rd position and in the case of 11 and 12, the arms were replaced with aliphatic chains. Our study demonstrates that for all four ligands, the RCM reactions only result in the formation of macrocyclic structures, which in three of the cases, were structurally characterised in both solution (using NMR and HRMS) and in the solid-state using X-ray crystallography. NMR studies were also carried out to investigate if these ligands could preorganise in solution via hydrogen bonding interactions. This study provides a handle of how such precursor substitution can be used to direct the formation of macrocycles or mechanically interlocked structures.

Mechanically Interlocked Chiral Self-Templated [2]Catenanes from 2,6-Bis(1,2,3-triazol-4-yl)pyridine (btp) Ligands

We report the efficient self-templated formation of optically active 2,6-bis(1,2,3-triazol-4-yl)pyridine (btp) derived homocircuit [2]catenane enantiomers. This represents the first example of the enantiopure formation of chiral btp homocircuit [2]catenanes from starting materials consisting of a classical chiral element; X-ray diffraction crystallography enabled the structural characterization of the [2]catenane. The self-assembly reaction was monitored closely in solution facilitating the characterization of the pseudo-rotaxane reaction intermediate prior to mechanically interlocking the pre-organised system via ring-closing metathesis.

Ruthenium-centred btp glycoclusters as inhibitors for Pseudomonas aeruginosa biofilm formation

Carbohydrate-decorated clusters (glycoclusters) centred on a Ru(ii) ion were synthesised and tested for their activity against Pseudomonas aeruginosa biofilm formation. These clusters were designed by conjugating a range of carbohydrate motifs (galactose, glucose, mannose and lactose, as well as galactose with a triethylene glycol spacer) to a btp (2,6-bis(1,2,3-triazol-4-yl)pyridine) scaffold. This scaffold, which possesses a C₂ symmetry, is an excellent ligand for d-metal ions, and thus the formation of the Ru(ii)-centred glycoclusters 7 and 8Gal was achieved from 5 and 6Gal; each possessing four deprotected carbohydrates. Glycocluster 8Gal, which has a flexible spacer between the btp and galactose moieties, showed significant inhibition of P. aeruginosa bacterial biofilm formation. By contrast, glycocluster 7, which lacked the flexible linker, didn't show significant antimicrobial effects and neither does the ligand 6Gal alone. These results are proposed to arise from carbohydrate–lectin interactions with LecA, which are possible for the flexible metal-centred multivalent glycocluster. Metal-centred glycoclusters present a structurally versatile class of antimicrobial agent for P. aeruginosa, of which this is, to the best of our knowledge, the first example.

Ruthenium-centred glycoclusters based on carbohydrate-functionalised bis(triazolyl)pyridine ligands show Pseudomonas aeruginosa biofilm inhibition, with activity that is dependent on ligand structure.

Highlights of the development and application of luminescent lanthanide based coordination polymers, MOFs and functional nanomaterials

The development of lanthanide based coordination polymer and metal-organic framework (CPs and MOFs) nanomaterials as novel functional (e.g. luminescent and magnetic) materials has attracted significant attention in recent times. This is in part due to the wide, but yet unique coordination requirements that the f-metal ions possess, as well as their attractive physical properties, which are often transferred to the bulk material. Hence, there is no surprise, that the design, synthesis and characterisation of lanthanide based CP/MOF materials (featuring either 'pure' lanthanides, or a mixture of both f- and d-metal ions) for applications in gas and small molecule absorption, storage, conversion/catalysis, chemical sensing, bio-imaging, drug delivery, etc. has been a prominent feature in the scientific literature. In this review, we give a selected overview of some of the recent developments in the area of Ln CP/MOF based nanomaterials for sensing, optical materials and bio-medicine research, as well as making reference to some more established examples, with the view of introducing, particularly to new researchers to the field, the powerful and attractive features of lanthanide based materials.

Balancing connectivity with function in silver(i) networks of pyridyltriazole (tzpa) ligands results in the formation of a metallogel

A new flexible and divergent 1,2,3-triazol-4-yl-picolinamide (tzpa) ligand 2 and the half-equivalent model ligand 1, both functionalised with pendant 3-pyridyl groups, are reported and their coordination behaviour with silver(i) ions is explored, both in the crystalline phase and through the formation of a supramolecular metallogel. The self-assembly of tzpa ligand 1 with AgCF3SO3 resulted in the formation of a 1D coordination polymer, binding in a bidentate fashion through the pyridyl and triazole nitrogen atoms of the tzpa binding site and a pendant pyridyl nitrogen atom of an adjacent ligand. Doubling the number of metal binding sites in ligand 2, while retaining the same metal binding domain, gives rise to the formation of a supramolecular metallogel on reaction with AgBF4 at 5 wt% in MeCN, possessing self-healing properties.

Structural properties of the chelating agent 2,6-bis(1-(3-hydroxypropyl)-1,2,3-triazol-4-yl)pyridine: a combined XRD and DFT structural study

The conformational isomerism of the chelating agent 2,6-bis(1-(3-hydroxypropyl)-1,2,3-triazol-4-yl)pyridine (PTD), exploited in fuel reprocessing in spent nuclear waste, has been studied by single crystal X-ray diffraction analysis in combination with an extensive DFT conformational investigation. In the solid-state, the elucidated crystal structure (i.e., not yet published) shows that by thermal treatment (DSC) no other phases are observed upon crystallization from the melt, indicating that the conformation observed by X-ray data is rather stable. Mapping of intermolecular and intramolecular noncovalent interactions has been used to elucidate the unusual arrangement of the asymmetric unit. Considerations relating to the stability of different conformational isomers in aqueous and non-aqueous solutions are also presented. The accurate structural description reported here might open various research topics such as the potential of PTD to act as an outer sphere ligand in the formation of second sphere coordination complexes and their interconversion by mechanochemical means.

Unexpected linkage isomerism in chiral tetranuclear bis-tridentate (1,2,3-triazol-4-yl)-picolinamide (tzpa) grids

The synthesis of a chiral bis-tridentate (1,2,3-triazol-4-yl)-picolinamide (tzpa) ligand is described and its coordination chemistry with Cu(NO3)2 and [Cu(MeCN)4]PF6 is explored in the crystalline phase as well as in solution. Chiral [2 × 2] tetranuclear square grid complexes [Cu4(H21)4](NO3)8 and [Cu4(H1)4](PF6)4 were observed, and crystallographically analysed, these being linkage isomers with N4O2 and N5O coordination spheres, respectively. These come about by an unusual in situ amide deprotonation and coordination, which accompanies a CuI → CuII oxidation process.

An excellently stable TbIII–organic framework with outstanding stability as a rapid, reversible, and multi-responsive luminescent sensor in water

A multi-response Tb-based metal–organic framework with excellent stability is used as a rapid and reversible luminescent sensor for Fe³⁺, Cr₂O₇²⁻, and nitrofurantoin in water.

Exploring the reversible host–guest chemistry of a crystalline octanuclear Ag(i) metallosupramolecular macrocycle formed from a simple pyrazinylpyridine ligand

High nuclearity Ag(i) assemblies are prepared from simple polytopic ligands, including an octanuclear metallomacrocycle which exhibits reversible and selective guest exchange.